Dr Paul Newton

Research Area: Clinical Epidemiology
Scientific Themes: Tropical Medicine & Global Health
Laboratories at dusk, Laos

Laboratories at dusk, Laos

We are a small clinical tropical medicine research group, the Wellcome Trust-Mahosot Hospital-Oxford Tropical Medicine Research Collaboration, based at Mahosot Hospital, Vientiane in Laos. Vientiane is a small capital city, on the banks of the Mekong River, of a country of 6 million people, but of the size of the UK. We are embedded in the Microbiology Laboratory of the Hospital and linked to the Mahidol University Oxford University Research Unit (MORU) in Bangkok, Thailand. The research is funded by the Wellcome Trust (UK).

The main aim of our work is to provide Lao health workers and the Lao Government with key data that will help make evidence-based decisions for individual patients and for health policy. The conditions we concentrate on include malaria, scrub typhus, murine typhus, melioidosis, dengue, leptospirosis, the causes of central nervous system infections and hepatitis/jaundice. We are also investigating diseases of nutrition and poverty such as infantile beriberi and noma.

We are particularly interested in the public health importance of diseases such scrub typhus and murine typhus, which were previously unrecognised, and the causes of community-acquired bacteraemia. Early work demonstrated the importance of local knowledge in deciding policy and the heterogeneity of infectious epidemiology in rural Asia. We also perform clinical trials on malaria, typhoid, murine typhus and scrub typhus treatment and evaluate rapid diagnostic tests for key diseases. We coordinate and conduct research on a Cinderella of medical specialties – medicine quality - especially the severe public health problem of counterfeit antimalarials in Asia and Africa.

We build human medical research capacity in Laos and produce a Lao and English language medical journal – the Mahosot Microbiology Review.

There are no collaborations listed for this principal investigator.

Caillet C, Syhakhang L, Delpierre C, Manithip C, Mayxay M, Buisson Y, Lapeyre-Mestre M, Newton P, Roussin A. 2014. Healthcare providers and population's knowledge regarding the risks related to medicinal products use: a cross-sectional study conducted in Laos FUNDAMENTAL & CLINICAL PHARMACOLOGY, 28 pp. 61-61.

Caillet C, Sichanh C, Mayxay M, Syhakhang L, Lapeyre-Mestre M, Roussin A, Newton P. 2014. Visual identification of single units of medicines for pharmacoepidemiological studies in developing countries: a pilot study in Lao PDR FUNDAMENTAL & CLINICAL PHARMACOLOGY, 28 pp. 102-102.

Tabernero P, Fernández FM, Green M, Guerin PJ, Newton PN. 2014. Mind the gaps--the epidemiology of poor-quality anti-malarials in the malarious world--analysis of the WorldWide Antimalarial Resistance Network database. Malar J, 13 (1), pp. 139. Read abstract | Read more

Poor quality medicines threaten the lives of millions of patients and are alarmingly common in many parts of the world. Nevertheless, the global extent of the problem remains unknown. Accurate estimates of the epidemiology of poor quality medicines are sparse and are influenced by sampling methodology and diverse chemical analysis techniques. In order to understand the existing data, the Antimalarial Quality Scientific Group at WWARN built a comprehensive, open-access, global database and linked Antimalarial Quality Surveyor, an online visualization tool. Analysis of the database is described here, the limitations of the studies and data reported, and their public health implications discussed. Hide abstract

Elliott I, Mayxay M, Yeuichaixong S, Lee SJ, Newton PN. 2014. The practice and clinical implications of tablet splitting in international health. Trop Med Int Health, 19 (7), pp. 754-760. Read abstract | Read more

Tablet splitting is frequently performed to facilitate correct dosing, but the practice and implications in low-income settings have rarely been discussed. Hide abstract

Dittrich S, Castonguay-Vanier J, Moore CE, Thongyoo N, Newton PN, Paris DH. 2014. Loop-mediated isothermal amplification for Rickettsia typhi (the causal agent of murine typhus): Problems with diagnosis at the limit of detection Journal of Clinical Microbiology, 52 (3), pp. 832-838. Read abstract | Read more

Murine typhus is a flea-borne disease of worldwide distribution caused by Rickettsia typhi. Although treatment with tetracycline antibiotics is effective, treatment is often misguided or delayed due to diagnostic difficulties. As the gold standard immunofluorescence assay is imperfect, we aimed to develop and evaluate a loop-mediated isothermal amplification (LAMP) assay. LAMP assays have the potential to fulfill the WHO ASSURED criteria (affordable, sensitive, specific, user friendly, robust and rapid, equipment free, deliverable to those who need them) for diagnostic methodologies, as they can detect pathogen-derived nucleic acid with low technical expenditure. The LAMP assay was developed using samples of bacterial isolates (n=41), buffy coat specimens from R. typhi PCR-positive Lao patients (n=42), and diverse negative controls (n=47). The method was then evaluated prospectively using consecutive patients with suspected scrub typhus or murine typhus (n=266). The limit of detection was ∼40 DNA copies/LAMP reaction, with an analytical sensitivity of<10 DNA copies/reaction based on isolate dilutions. Despite these low cutoffs, the clinical sensitivity was disappointing, with 48% (95% confidence interval [95% CI], 32.5 to 62.7%) (specificity, 100% [95% CI, 100 to 100%]) in the developmental phase and 33% (95% CI, 9.2 to 56.8%) (specificity, 98.5% [95% CI, 97.0% to 100%]) in the prospective study. This low diagnostic accuracy was attributed to low patient R. typhi bacterial loads (median, 210 DNA copies/ml blood; interquartile range, 130 to 500). PCR-positive but LAMP-negative samples demonstrated significantly lower bacterial loads than LAMP-positive samples. Our findings highlight the diagnostic challenges for diseases with low pathogen burdens and emphasize the need to integrate pathogen biology with improved template production for assay development strategies. Copyright © 2014 Dittrich et al. Hide abstract

Moyes CL, Henry AJ, Golding N, Huang Z, Singh B, Baird JK, Newton PN, Huffman M et al. 2014. Defining the geographical range of the Plasmodium knowlesi reservoir. PLoS Negl Trop Dis, 8 (3), pp. e2780. Read abstract | Read more

The simian malaria parasite, Plasmodium knowlesi, can cause severe and fatal disease in humans yet it is rarely included in routine public health reporting systems for malaria and its geographical range is largely unknown. Because malaria caused by P. knowlesi is a truly neglected tropical disease, there are substantial obstacles to defining the geographical extent and risk of this disease. Information is required on the occurrence of human cases in different locations, on which non-human primates host this parasite and on which vectors are able to transmit it to humans. We undertook a systematic review and ranked the existing evidence, at a subnational spatial scale, to investigate the potential geographical range of the parasite reservoir capable of infecting humans. Hide abstract

Monge ME, Dwivedi P, Zhou M, Payne M, Harris C, House B, Juggins Y, Cizmarik P, Newton PN, Fernández FM, Jenkins D. 2014. A tiered analytical approach for investigating poor quality emergency contraceptives. PLoS One, 9 (4), pp. e95353. Read abstract | Read more

Reproductive health has been deleteriously affected by poor quality medicines. Emergency contraceptive pills (ECPs) are an important birth control method that women can use after unprotected coitus for reducing the risk of pregnancy. In response to the detection of poor quality ECPs commercially available in the Peruvian market we developed a tiered multi-platform analytical strategy. In a survey to assess ECP medicine quality in Peru, 7 out of 25 different batches showed inadequate release of levonorgestrel by dissolution testing or improper amounts of active ingredient. One batch was found to contain a wrong active ingredient, with no detectable levonorgestrel. By combining ultrahigh performance liquid chromatography-ion mobility spectrometry-mass spectrometry (UHPLC-IMS-MS) and direct analysis in real time MS (DART-MS) the unknown compound was identified as the antibiotic sulfamethoxazole. Quantitation by UHPLC-triple quadrupole tandem MS (QqQ-MS/MS) indicated that the wrong ingredient was present in the ECP sample at levels which could have significant physiological effects. Further chemical characterization of the poor quality ECP samples included the identification of the excipients by 2D Diffusion-Ordered Nuclear Magnetic Resonance Spectroscopy (DOSY 1H NMR) indicating the presence of lactose and magnesium stearate. Hide abstract

Dubot-Pérès A, Tan CY, de Chesse R, Sibounheuang B, Vongsouvath M, Phommasone K, Bessaud M, Gazin C et al. 2014. SYBR green real-time PCR for the detection of all enterovirus-A71 genogroups. PLoS One, 9 (3), pp. e89963. Read abstract | Read more

Enterovirus A71 (EV-A71) has recently become an important public health threat, especially in South-East Asia, where it has caused massive outbreaks of Hand, Foot and Mouth disease every year, resulting in significant mortality. Rapid detection of EV-A71 early in outbreaks would facilitate implementation of prevention and control measures to limit spread. Real-time RT-PCR is the technique of choice for the rapid diagnosis of EV-A71 infection and several systems have been developed to detect circulating strains. Although eight genogroups have been described globally, none of these PCR techniques detect all eight. We describe, for the first time, a SYBR Green real-time RT-PCR system validated to detect all 8 EV-A71 genogroups. This tool could permit the early detection and shift in genogroup circulation and the standardization of HFMD virological diagnosis, facilitating networking of laboratories working on EV-A71 in different regions. Hide abstract

Tanomsing N, Mayxay M, Newton PN, Nosten F, Dolecek C, Hien TT, White NJ, Day NP, Dondorp AM, Imwong M. 2014. Genetic variability of Plasmodium malariae dihydropteroate synthase (dhps) in four Asian countries. PLoS One, 9 (4), pp. e93942. Read abstract | Read more

The dihydropteroate synthase (dhps) genes of 44 P. malariae strains from four Asian countries were isolated. Only a limited number of polymorphisms were observed. Comparison with homologous mutations in other Plasmodium species showed that these polymorphisms are unlikely to be associated with sulfadoxine resistance. Hide abstract

Tarantola A, Goutard F, Newton P, de Lamballerie X, Lortholary O, Cappelle J, Buchy P. 2014. Estimating the burden of Japanese encephalitis virus and other encephalitides in countries of the mekong region. PLoS Negl Trop Dis, 8 (1), pp. e2533. Read abstract | Read more

Diverse aetiologies of viral and bacterial encephalitis are widely recognized as significant yet neglected public health issues in the Mekong region. A robust analysis of the corresponding health burden is lacking. We retrieved 75 articles on encephalitis in the region published in English or in French from 1965 through 2011. Review of available data demonstrated that they are sparse and often derived from hospital-based studies with significant recruitment bias. Almost half (35 of 75) of articles were on Japanese encephalitis virus (JEV) alone or associated with dengue. In the Western Pacific region the WHO reported 30,000-50,000 annual JEV cases (15,000 deaths) between 1966 and 1996 and 4,633 cases (200 deaths) in 2008, a decline likely related to the introduction of JEV vaccination in China, Vietnam, or Thailand since the 1980s. Data on dengue, scrub typhus and rabies encephalitis, among other aetiologies, are also reviewed and discussed. Countries of the Mekong region are undergoing profound demographic, economic and ecological change. As the epidemiological aspects of Japanese encephalitis (JE) are transformed by vaccination in some countries, highly integrated expert collaborative research and objective data are needed to identify and prioritize the human health, animal health and economic burden due to JE and other pathogens associated with encephalitides. Hide abstract

Culzoni MJ, Dwivedi P, Green MD, Newton PN, Fernandez FM. 2014. Ambient mass spectrometry technologies for the detection of falsified drugs MEDCHEMCOMM, 5 (1), pp. 9-19. Read abstract | Read more

Increased globalization of the pharmaceutical market has facilitated the unobstructed and fast spread of poor-quality medicines. Poor-quality medicines include spurious/falsely-labeled/falsified/counterfeit drugs (those that are deliberately and fraudulently mislabeled with respect to content and/or origin), substandard drugs (legitimate drugs that do not meet their quality specifications), and degraded medicines (good quality pharmaceuticals that suffered from deterioration caused by improper storage or distribution). Consumption of poor-quality pharmaceuticals is likely to increase morbidity and mortality. Moreover, poor-quality drugs can also contribute to the development of resistance to anti-infective medicines and decrease the quality of health care received by patients. To assess the true prevalence of poor quality drugs, tiered technology approaches enabling the testing of drug samples collected at points of sale are required, thus ensuring public health standards. High throughput and high resolution ambient mass spectrometry techniques allow investigation of pharmaceuticals with minimal or no sample preparation, thus possessing capabilities to survey a large number of drug samples for their authenticity. © 2014 The Royal Society of Chemistry. Hide abstract

Dittrich S, Castonguay-Vanier J, Moore CE, Thongyoo N, Newton PN, Paris DH. 2014. Loop-mediated isothermal amplification for Rickettsia typhi (the causal agent of murine typhus): problems with diagnosis at the limit of detection. J Clin Microbiol, 52 (3), pp. 832-838. Read abstract | Read more

Murine typhus is a flea-borne disease of worldwide distribution caused by Rickettsia typhi. Although treatment with tetracycline antibiotics is effective, treatment is often misguided or delayed due to diagnostic difficulties. As the gold standard immunofluorescence assay is imperfect, we aimed to develop and evaluate a loop-mediated isothermal amplification (LAMP) assay. LAMP assays have the potential to fulfill the WHO ASSURED criteria (affordable, sensitive, specific, user friendly, robust and rapid, equipment free, deliverable to those who need them) for diagnostic methodologies, as they can detect pathogen-derived nucleic acid with low technical expenditure. The LAMP assay was developed using samples of bacterial isolates (n=41), buffy coat specimens from R. typhi PCR-positive Lao patients (n=42), and diverse negative controls (n=47). The method was then evaluated prospectively using consecutive patients with suspected scrub typhus or murine typhus (n=266). The limit of detection was ∼40 DNA copies/LAMP reaction, with an analytical sensitivity of <10 DNA copies/reaction based on isolate dilutions. Despite these low cutoffs, the clinical sensitivity was disappointing, with 48% (95% confidence interval [95% CI], 32.5 to 62.7%) (specificity, 100% [95% CI, 100 to 100%]) in the developmental phase and 33% (95% CI, 9.2 to 56.8%) (specificity, 98.5% [95% CI, 97.0% to 100%]) in the prospective study. This low diagnostic accuracy was attributed to low patient R. typhi bacterial loads (median, 210 DNA copies/ml blood; interquartile range, 130 to 500). PCR-positive but LAMP-negative samples demonstrated significantly lower bacterial loads than LAMP-positive samples. Our findings highlight the diagnostic challenges for diseases with low pathogen burdens and emphasize the need to integrate pathogen biology with improved template production for assay development strategies. Hide abstract

Smit PW, Elliott I, Peeling RW, Mabey D, Newton PN. 2014. An overview of the clinical use of filter paper in the diagnosis of tropical diseases. Am J Trop Med Hyg, 90 (2), pp. 195-210. Read abstract | Read more

Tropical infectious diseases diagnosis and surveillance are often hampered by difficulties of sample collection and transportation. Filter paper potentially provides a useful medium to help overcome such problems. We reviewed the literature on the use of filter paper, focusing on the evaluation of nucleic acid and serological assays for diagnosis of infectious diseases using dried blood spots (DBS) compared with recognized gold standards. We reviewed 296 eligible studies and included 101 studies evaluating DBS and 192 studies on other aspects of filter paper use. We also discuss the use of filter paper with other body fluids and for tropical veterinary medicine. In general, DBS perform with sensitivities and specificities similar or only slightly inferior to gold standard sample types. However, important problems were revealed with the uncritical use of DBS, inappropriate statistical analysis, and lack of standardized methodology. DBS have great potential to empower healthcare workers by making laboratory-based diagnostic tests more readily accessible, but additional and more rigorous research is needed. Hide abstract

Achan J, Adam I, Arinaitwe E, Ashley EA, Awab GR, Ba MS, Barnes KI, Bassat Q et al. 2013. The Effect of Dosing Regimens on the Antimalarial Efficacy of Dihydroartemisinin-Piperaquine: A Pooled Analysis of Individual Patient Data PLOS MEDICINE, 10 (12), pp. e1001564-e1001564. Read abstract | Read more

Background:Dihydroartemisinin-piperaquine (DP) is increasingly recommended for antimalarial treatment in many endemic countries; however, concerns have been raised over its potential under dosing in young children. We investigated the influence of different dosing schedules on DP's clinical efficacy.Methods and Findings:A systematic search of the literature was conducted to identify all studies published between 1960 and February 2013, in which patients were enrolled and treated with DP. Principal investigators were approached and invited to share individual patient data with the WorldWide Antimalarial Resistance Network (WWARN). Data were pooled using a standardised methodology. Univariable and multivariable risk factors for parasite recrudescence were identified using a Cox's regression model with shared frailty across the study sites. Twenty-four published and two unpublished studies (n = 7,072 patients) were included in the analysis. After correcting for reinfection by parasite genotyping, Kaplan-Meier survival estimates were 97.7% (95% CI 97.3%-98.1%) at day 42 and 97.2% (95% CI 96.7%-97.7%) at day 63. Overall 28.6% (979/3,429) of children aged 1 to 5 years received a total dose of piperaquine below 48 mg/kg (the lower limit recommended by WHO); this risk was 2.3-2.9-fold greater compared to that in the other age groups and was associated with reduced efficacy at day 63 (94.4% [95% CI 92.6%-96.2%], p<0.001). After adjusting for confounding factors, the mg/kg dose of piperaquine was found to be a significant predictor for recrudescence, the risk increasing by 13% (95% CI 5.0%-21%) for every 5 mg/kg decrease in dose; p = 0.002. In a multivariable model increasing the target minimum total dose of piperaquine in children aged 1 to 5 years old from 48 mg/kg to 59 mg/kg would halve the risk of treatment failure and cure at least 95% of patients; such an increment was not associated with gastrointestinal toxicity in the ten studies in which this could be assessed.Conclusions:DP demonstrates excellent efficacy in a wide range of transmission settings; however, treatment failure is associated with a lower dose of piperaquine, particularly in young children, suggesting potential for further dose optimisation.Please see later in the article for the Editors' Summary. © 2013 Price et al. Hide abstract

Flegg JA, Guérin PJ, Nosten F, Ashley EA, Phyo AP, Dondorp AM, Fairhurst RM, Socheat D et al. 2013. Optimal sampling designs for estimation of Plasmodium falciparum clearance rates in patients treated with artemisinin derivatives. Malar J, 12 (1), pp. 411. Read abstract | Read more

The emergence of Plasmodium falciparum resistance to artemisinins in Southeast Asia threatens the control of malaria worldwide. The pharmacodynamic hallmark of artemisinin derivatives is rapid parasite clearance (a short parasite half-life), therefore, the in vivo phenotype of slow clearance defines the reduced susceptibility to the drug. Measurement of parasite counts every six hours during the first three days after treatment have been recommended to measure the parasite clearance half-life, but it remains unclear whether simpler sampling intervals and frequencies might also be sufficient to reliably estimate this parameter. Hide abstract

Elliott I, Dittrich S, Paris D, Sengduanphachanh A, Phoumin P, Newton PN. 2013. The use of dried cerebrospinal fluid filter paper spots as a substrate for PCR diagnosis of the aetiology of bacterial meningitis in the Lao PDR Clinical Microbiology and Infection, 19 (10), Read abstract | Read more

We investigated whether dried cerebrospinal fluid (CSF) conserved on filter paper can be used as a substrate for accurate PCR diagnosis of important causes of bacterial meningitis in the Lao PDR. Using mock CSF, we investigated and optimized filter paper varieties, paper punch sizes, elution volumes and quantities of DNA template to achieve sensitive and reliable detection of bacterial DNA from filter paper specimens. FTA Elute Micro Card™ (Whatman, Maidstone, UK) was the most sensitive, consistent and practical variety of filter paper. Following optimization, the lower limit of detection for Streptococcus pneumoniae from dried mock CSF spots was 14 genomic equivalents (GE)/μL (interquartile range 5.5 GE/μL) or 230 (IQR 65) colony forming units/mL. A prospective clinical evaluation for S. pneumoniae, S. suis and Neisseria meningitidis was performed. Culture and PCR performed on fresh liquid CSF from patients admitted with a clinical diagnosis of meningitis (n = 73) were compared with results derived from dried CSF spots. Four of five fresh PCR-positive CSF samples also tested PCR positive from dried CSF spots, with one patient under the limit of detection. In a retrospective study of S. pneumoniae samples (n = 20), the median (IQR; range) CSF S. pneumoniae bacterial load was 1.1 × 104 GE/μL (1.2 × 105; 1 to 6.1 × 106 DNA GE/μL). Utilizing the optimized methodology, we estimate an extrapolated sensitivity of 90%, based on the range of CSF genome counts found in Laos. Dried CSF filter paper spots could potentially help us to better understand the epidemiology of bacterial meningitis in resource-poor settings and guide empirical treatments and vaccination policies. © 2013 The Authors. Clinical Microbiology and Infection published by John Wiley & Sons Ltd on behalf of the European Society of Clinical Microbiology and Infectious Disease. Hide abstract

Mayxay M, Castonguay-Vanier J, Chansamouth V, Dubot-Pérès A, Paris DH, Phetsouvanh R, Tangkhabuanbutra J, Douangdala P et al. 2013. Causes of non-malarial fever in Laos: a prospective study. Lancet Glob Health, 1 (3), pp. e46-e54. Read abstract | Read more

Because of reductions in the incidence of Plasmodium falciparum malaria in Laos, identification of the causes of fever in people without malaria, and discussion of the best empirical treatment options, are urgently needed. We aimed to identify the causes of non-malarial acute fever in patients in rural Laos. Hide abstract

Plancon A, Newton P. 2013. Building bridges between law enforcement and public health communities to combat pharmaceutical crime TROPICAL MEDICINE & INTERNATIONAL HEALTH, 18 pp. 20-20.

Newton P. 2013. Causes of fever - hoof beats are rarely from zebras TROPICAL MEDICINE & INTERNATIONAL HEALTH, 18 pp. 7-7.

Phommasone K, Paris DH, Anantatat T, Castonguay-Vanier J, Keomany S, Souvannasing P, Blacksell SD, Mayxay M, Newton PN. 2013. Concurrent Infection with murine typhus and scrub typhus in southern Laos--the mixed and the unmixed. PLoS Negl Trop Dis, 7 (8), pp. e2163. | Read more

Dubot-Pérès A, Vongphrachanh P, Denny J, Phetsouvanh R, Linthavong S, Sengkeopraseuth B, Khasing A, Xaythideth V et al. 2013. An epidemic of dengue-1 in a remote village in rural Laos. PLoS Negl Trop Dis, 7 (8), pp. e2360. Read abstract | Read more

In the Lao PDR (Laos), urban dengue is an increasingly recognised public health problem. We describe a dengue-1 virus outbreak in a rural northwestern Lao forest village during the cool season of 2008. The isolated strain was genotypically "endemic" and not "sylvatic," belonging to the genotype 1, Asia 3 clade. Phylogenetic analyses of 37 other dengue-1 sequences from diverse areas of Laos between 2007 and 2010 showed that the geographic distribution of some strains remained focal overtime while others were dispersed throughout the country. Evidence that dengue viruses have broad circulation in the region, crossing country borders, was also obtained. Whether the outbreak arose from dengue importation from an urban centre into a dengue-naïve community or crossed into the village from a forest cycle is unknown. More epidemiological and entomological investigations are required to understand dengue epidemiology and the importance of rural and forest dengue dynamics in Laos. Hide abstract

Anderson M, Luangxay K, Sisouk K, Vorlasan L, Soumphonphakdy B, Sengmouang V, Chansamouth V, Phommasone K et al. 2014. Epidemiology of bacteremia in young hospitalized infants in Vientiane, Laos, 2000-2011. J Trop Pediatr, 60 (1), pp. 10-16. Read abstract | Read more

As data about the causes of neonatal sepsis in low-income countries are inadequate, we reviewed the etiology and antibiotic susceptibilities of bacteremia in young infants in Laos. As Staphylococcus aureus is the leading cause of bacteremia in Lao infants, we also examined risk factors for this infection, in particular the local practice of warming mothers during the first weeks postpartum with hot coals under their beds (hot beds). Clinical and laboratory data regarding infants aged 0-60 days evaluated for sepsis within 72 h of admission to Mahosot Hospital in Vientiane, Laos, were reviewed, and 85 of 1438 (5.9%) infants' blood cultures grew a clinically significant organism. Most common were S. aureus, Escherichia coli and Klebsiella pneumoniae. Whereas no methicillin-resistant S. aureus was found, only 18% of E. coli isolates were susceptible to ampicillin. A history of sleeping on a hot bed with mother was associated with S. aureus bacteremia (odds ratio 4.8; 95% confidence interval 1.2-19.0). Hide abstract

Newton PN, Stepniewska K, Dondorp A, Silamut K, Chierakul W, Krishna S, Davis TM, Suputtamongkol Y et al. 2013. Prognostic indicators in adults hospitalized with falciparum malaria in Western Thailand. Malar J, 12 (1), pp. 229. Read abstract | Read more

Severe malaria remains a major cause of death and morbidity amongst adults in the Asiatic tropics. Hide abstract

Jiang J, Paris DH, Blacksell SD, Aukkanit N, Newton PN, Phetsouvanh R, Izzard L, Stenos J, Graves SR, Day NP, Richards AL. 2013. Diversity of the 47-kD HtrA nucleic acid and translated amino acid sequences from 17 recent human isolates of Orientia. Vector Borne Zoonotic Dis, 13 (6), pp. 367-375. Read abstract | Read more

Orientia tsutsugamushi, the etiologic agent of potentially fatal scrub typhus, is characterized by a high antigenic diversity, which complicates the development of a broadly protective vaccine. Efficacy studies in murine and nonhuman primate models demonstrated the DNA vaccine candidate pKarp47, based upon the O. tsutsugamushi Karp 47-kD HtrA protein gene, to be a successful immunoprophylactic against scrub typhus. To characterize 47-kD HtrA protein diversity among human isolates of Orientia, we sequenced the full open reading frame (ORF) of the 47-kD HtrA gene and analyzed the translated amino acid sequences of 17 patient isolates from Thailand (n=13), Laos (n=2), Australia (n=1), and the United Arab Emirates (UAE) (n=1) and 9 reference strains: Karp (New Guinea), Kato (Japan), Ikeda (Japan), Gilliam (Burma), Boryong (Korea), TA763, TH1811 and TH1817 (Thailand), and MAK243 (China). The percentage identity (similarity) of translated amino acid sequences between 16 new isolates and 9 reference strains of O. tsutsugamushi ranged from 96.4% to 100% (97.4% to 100%). However, inclusion of the recently identified Orientia chuto sp. nov. reduced identity (similarity) values to 82.2% to 83.3% (90.4% to 91.4%). These results demonstrate the diversity of Orientia 47-kD HtrA among isolates encountered by humans and therefore provide support for the necessity of developing a broadly protective scrub typhus vaccine that takes this diversity into account. Hide abstract

Phetsouvanh R, Thojaikong T, Phoumin P, Sibounheuang B, Phommasone K, Chansamouth V, Lee SJ, Newton PN, Blacksell SD. 2013. Inter- and intra-operator variability in the reading of indirect immunofluorescence assays for the serological diagnosis of scrub typhus and murine typhus. Am J Trop Med Hyg, 88 (5), pp. 932-936. Read abstract | Read more

Inter- and intra-observer variation was examined among six microscopists who read 50 scrub typhus (ST) and murine typhus (MT) indirect immunofluorescence assay (IFA) immunoglobulin M (IgM) slides. Inter-observer agreement was moderate (κ = 0.45) for MT and fair (κ = 0.32) for ST, and was significantly correlated with experience (P = 0.03 and P = 0.004, respectively); κ-scores for intra-observer agreement between morning and afternoon readings (range = 0.35-0.86) were not correlated between years of experience for ST and MT IFAs (Spearman's ρ = 0.31, P = 0.54 and P = 0.14, respectively; P = 0.78). Storage at 4°C for 2 days showed a change from positive to negative in 20-32% of slides. Although the titers did not dramatically change after 14 days of storage, the final interpretation (positive to negative) did change in 36-50% of samples, and it, therefore, recommended that slides should be read as soon as possible after processing. Hide abstract

Green MD, Mayxay M, Beach R, Pongvongsa T, Phompida S, Hongvanthong B, Vanisaveth V, Newton PN, Vizcaino L, Swamidoss I. 2013. Evaluation of a rapid colorimetric field test to assess the effective life of long-lasting insecticide-treated mosquito nets in the Lao PDR. Malar J, 12 (1), pp. 57. Read abstract | Read more

Malaria morbidity and mortality have been significantly reduced through the proper use of insecticide-treated mosquito nets, but the extra protection afforded by the insecticide diminishes over time. The insecticide depletion rates vary according to location where wash frequency and wear are influenced by cultural habits as well as the availability of water. Monitoring of available insecticides on the net surface is essential for determining the effective life of the net. Therefore, a rapid and inexpensive colorimetric field test for cyanopyrethroids (Cyanopyrethroid Field Test or CFT) was used to measure surface levels of deltamethrin on insecticide-coated polyester nets (PowerNets™) in rural Lao PDR over a two-year period. Hide abstract

Wang H, Yuan Z, Li G, Barnes E, Klenerman P, Yuan M, Li C, Lu L et al. 2013. Eight novel hepatitis c virus genomes reveal the changing taxonomic structure of genotype 6 Journal of General Virology, 94 (PART11), pp. 76-80. Read abstract | Read more

Analysis of partial hepatitis C virus sequences has revealed many novel genotype 6 variants that cannot be unambiguously classified, which obscure the distinctiveness of pre-existing subtypes. To explore this uncertainty, we obtained genomes of 98.0-98.8% full-length for eight such variants (KM35, QC273, TV257, TV476, TV533, L349, QC271 and DH027) and characterized them using phylogenetic analyses and per cent nucleotide similarities. The former four are closely related phylogenetically to subtype 6k, TV533 and L349 to subtype 6l, QC271 to subtypes 6i and 6j, and DH027 to subtypes 6m and 6n. The former six defined a high-level grouping that comprised subtypes 6k and 6l, plus related strains. The threshold between intra- and intersubtype diversity in this group was indistinct. We propose that similar results would be seen elsewhere if more intermediate variants like QC271 and DH027 were sampled. © 2013 SGM. Hide abstract

Newton PN, Day NPJ. 2012. Scrub Typhus pp. 542-545. | Read more

Castonguay-Vanier J, Davong V, Bouthasavong L, Sengdetka D, Simmalavong M, Seupsavith A, Dance DA, Baker S, Le Thi Phuong T, Vongsouvath M, Newton PN. 2013. Evaluation of a simple blood culture amplification and antigen detection method for diagnosis of Salmonella enterica serovar typhi bacteremia. J Clin Microbiol, 51 (1), pp. 142-148. Read abstract | Read more

In most areas where typhoid is endemic, laboratory diagnosis is not possible due to the lack of appropriate facilities. We investigated whether the combination of blood culture amplification of Salmonella enterica serovar Typhi with an S. Typhi antigen rapid diagnostic test (RDT) could be an accurate and inexpensive tool for the accelerated diagnosis of patients with acute typhoid in Laos. For a panel of 23 Gram-negative reference pathogens, the Standard Diagnostics (catalog no. 15FK20; Kyonggi-do, South Korea) RDT gave positive results for S. Typhi NCTC 8385, S. Typhi NCTC 786 (Vi negative), Salmonella enterica serovar Enteritidis (ATCC 13076), and Salmonella enterica serovar Ndolo NCTC 8700 (all group D). In a prospective study of 6,456 blood culture bottles from 3,028 patients over 15 months, 392 blood culture bottles (6.1%) from 221 (7.3%) patients had Gram-negative rods (GNRs) seen in the blood culture fluid. The sensitivity, negative predictive value, specificity, and positive predictive value were 96.7%, 99.5%, 97.9%, and 87.9%, respectively, for patients with proven S. Typhi bacteremia and 91.2%, 98.4%, 98.9%, and 93.9% for patients with group D Salmonella. The median (range) number of days between diagnosis by RDT and reference assays was 1 (-1 to +2) day for those with confirmed S. Typhi. The use of antigen-based pathogen detection in blood culture fluid may be a useful, relatively rapid, inexpensive, and accurate technique for the identification of important causes of bacteremia in the tropics. Hide abstract

Lee SJ, Newton PN. 2012. Use of the correlation coefficient to compare a point-of-care antigen test against a quantitative sandwich enzyme-linked immunosorbent assay for the detection of cryptococcal meningitis. Clin Infect Dis, 55 (12), pp. 1744-1745. | Read more

Blacksell SD, Lee SJ, Chanthongthip A, Taojaikong T, Thongpaseuth S, Hübscher T, Newton PN. 2012. Comparison of performance of serum and plasma in panbio dengue and Japanese encephalitis virus enzyme-linked immunosorbent assays. Am J Trop Med Hyg, 87 (3), pp. 573-575. Read abstract | Read more

We examined the comparative performance of serum and plasma (in dipotassium EDTA) in Panbio Dengue enzyme-linked immunosorbent assays (ELISAs) for detection of non-structural protein 1 (NS1), IgM, and IgG, and a dengue/Japanese encephalitis virus (JEV) combination IgM ELISA in a prospective series of 201 patients with suspected dengue in Laos. Paired comparisons of medians from serum and plasma samples were not significantly different for Dengue IgM, and NS1 which had the highest number of discordant pairs (both 2%; P = 0.13 and P = 0.25, respectively). Comparison of qualitative final diagnostic interpretations for serum and plasma samples were not significantly different: only 1.5% (3 of 201 for Dengue/JEV IgM and Dengue IgG) and 2.0% (4 of 201; IgM and NS1) showed discordant pairs. These results demonstrate that plasma containing EDTA is suitable for use in these ELISAs. Hide abstract

Tanganuchitcharnchai A, Smythe L, Dohnt M, Hartskeerl R, Vongsouvath M, Davong V, Lattana O, Newton PN, Blacksell SD. 2012. Evaluation of the Standard Diagnostics Leptospira IgM ELISA for diagnosis of acute leptospirosis in Lao PDR. Trans R Soc Trop Med Hyg, 106 (9), pp. 563-566. Read abstract | Read more

The diagnostic utility of the Standard Diagnostics Leptospira IgM ELISA for detection of acute leptospirosis was assessed in febrile adults admitted in Vientiane, Laos. Using the cut-off suggested by the manufacturer [optical density (OD) ≥0.75], the assay demonstrated limited diagnostic capacity with a sensitivity of 95% and a specificity of 41% compared with the Leptospira microscopic agglutination test, which is the serological gold standard. However, re-evaluation of the diagnostic cut-off to an OD of 1.7 demonstrated improved diagnostic accuracy overall (sensitivity 70%; specificity 78%). Hide abstract

Moore CE, Blacksell SD, Taojaikong T, Jarman RG, Gibbons RV, Lee SJ, Chansamouth V, Thongpaseuth S, Mayxay M, Newton PN. 2012. A prospective assessment of the accuracy of commercial IgM ELISAs in diagnosis of Japanese encephalitis virus infections in patients with suspected central nervous system infections in Laos. Am J Trop Med Hyg, 87 (1), pp. 171-178. Read abstract | Read more

Japanese encephalitis virus (JEV) is a major cause of encephalitis in Asia. We estimated the diagnostic accuracy of two anti-JEV immunoglobulin M (IgM) enzyme-linked immunosorbent assays (ELISAs) (Panbio and XCyton JEVCheX) compared with a reference standard (AFRIMS JEV MAC ELISA) in a prospective study of the causes of central nervous system infections in Laos. Cerebrospinal fluid (CSF; 515 patients) and serum samples (182 patients) from those admitted to Mahosot Hospital, Vientiane, were tested. The CSF from 14.5% of acute encephalitis syndrome (AES) patients and 10.1% from those with AES and meningitis were positive for anti-JEV IgM in the reference ELISA. The sensitivities for CSF were 65.4% (95% confidence interval [CI] = 51-78) (Xcyton), 69.2% (95% CI = 55-81) (Panbio), however 96.2% (95% CI = 87-100) with Panbio Ravi criteria. Specificities were 89-100%. For admission sera from AES patients, sensitivities and specificities of the Panbio ELISA were 85.7% (95% CI = 42-100%) and 92.9% (95% CI = 83-98%), respectively. Hide abstract

Mayxay M, Khanthavong M, Chanthongthip O, Imwong M, Pongvongsa T, Hongvanthong B, Phompida S, Vanisaveth V, White NJ, Newton PN. 2012. Efficacy of artemether-lumefantrine, the nationally-recommended artemisinin combination for the treatment of uncomplicated falciparum malaria, in southern Laos. Malar J, 11 (1), pp. 184. Read abstract | Read more

The Lao Government changed the national policy for uncomplicated Plasmodium falciparum malaria from chloroquine to artemether-lumefantrine (AL) in 2005. Since then, no information on AL efficacy has been reported. With evidence of resistance to artemisinin derivatives in adjacent Cambodia, there has been a concern as to AL efficacy. Monitoring of AL efficacy would help the Lao Government to make decisions on appropriate malaria treatment. Hide abstract

Luangxay K, Sisouk K, Vorlasan L, Soumphonphakdy B, Sengmouang V, Anderson M, Chansamouth V, Phommasone K, Begue R, Newton P. 2012. High hospital incidence of Staphylococcus aureus bacteremia in young infants in the Lao PDR INTERNATIONAL JOURNAL OF INFECTIOUS DISEASES, 16 pp. E202-E203. | Read more

Vongphayloth K, Rattanavong S, Moore CE, Phetsouvanh R, Wuthiekanun V, Sengdouangphachanh A, Phouminh P, Newton PN, Buisson Y. 2012. Burkholderia pseudomallei detection in surface water in southern Laos using Moore's swabs. Am J Trop Med Hyg, 86 (5), pp. 872-877. Read abstract | Read more

The causal agent of melioidosis, Burkholderia pseudomallei, has been cultured from paddy fields in the Lao PDR. We carried out a pilot study to examine the relationship between bacterial soil contamination and that of nearby surface waters in Saravane Province. Soil sampling was conducted at a depth of 30 cm (100 holes in a 45 × 45 m grid) at two sites, East and West Saravane. Moore's swabs were used for water sampling of paddy fields, lakes, rivers, boreholes, and storage tanks within 2 km of the two soil sampling sites. B. pseudomallei from soil and water were cultured on Ashdown's agar. Thirty-six percent and 6% of water samples collected around East and West Saravane, respectively, were culture positive for B. pseudomallei. Low pH and high turbidity were independently associated with culture of B. pseudomallei. Most positive water samples were from the Sedone River, downstream of the East Saravane site. Moore's swabs are simple and inexpensive tools for detecting B. pseudomallei in surface waters. Hide abstract

Tabernero P, Newton PN. 2012. The WWARN antimalarial quality surveyor. Pathog Glob Health, 106 (2), pp. 77-78. | Read more

Newton P. 2012. Interview. Pathog Glob Health, 106 (2), pp. 69-71. | Read more

Mayxay M, Khanthavong M, Chanthongthip O, Imwong M, Lee SJ, Stepniewska K, Soonthornsata B, Pongvongsa T et al. 2012. No evidence for spread of Plasmodium falciparum artemisinin resistance to Savannakhet Province, Southern Laos. Am J Trop Med Hyg, 86 (3), pp. 403-408. Read abstract | Read more

We conducted an open-label, randomized clinical trial to assess parasite clearance times (PCT) and the efficacy of 4 mg/kg (group 1, n = 22) and 2 mg/kg (group 2, n = 22) of oral artesunate for three days followed by artemether-lumefantrine in patients with uncomplicated Plasmodium falciparum malaria at Xepon Interdistrict Hospital, Savannakhet Province in southern Laos. Slides were read in duplicate. The overall mean (95% confidence interval; range) PCT in hours was 23.2 (21.2-25.3; 12-46) and 22.4 (20.3-24.5; 12-46) for the first and second microscopists, respectively (P = 0.57). Ten (23%) patients remained parasitemic on day 1 after treatment (4 [18%] in group 1 and 6 [27%] in group 2; P = 0.47). No patient had patent asexual parasitemia on the second and third days of treatment. The 42-day polymerase chain reaction-corrected cure rates were 100% in both treatment groups. Serious adverse events did not develop during or after treatment in any patients. In conclusion, no evidence of P. falciparum in vivo resistance to artesunate was found in southern Laos. Hide abstract

Yalcindag E, Elguero E, Arnathau C, Durand P, Akiana J, Anderson TJ, Aubouy A, Balloux F et al. 2012. Multiple independent introductions of Plasmodium falciparum in South America. Proc Natl Acad Sci U S A, 109 (2), pp. 511-516. Read abstract | Read more

The origin of Plasmodium falciparum in South America is controversial. Some studies suggest a recent introduction during the European colonizations and the transatlantic slave trade. Other evidence--archeological and genetic--suggests a much older origin. We collected and analyzed P. falciparum isolates from different regions of the world, encompassing the distribution range of the parasite, including populations from sub-Saharan Africa, the Middle East, Southeast Asia, and South America. Analyses of microsatellite and SNP polymorphisms show that the populations of P. falciparum in South America are subdivided in two main genetic clusters (northern and southern). Phylogenetic analyses, as well as Approximate Bayesian Computation methods suggest independent introductions of the two clusters from African sources. Our estimates of divergence time between the South American populations and their likely sources favor a likely introduction from Africa during the transatlantic slave trade. Hide abstract

Nayyar GM, Breman JG, Newton PN, Herrington J. 2012. Poor-quality antimalarial drugs in southeast Asia and sub-Saharan Africa. Lancet Infect Dis, 12 (6), pp. 488-496. Read abstract | Read more

Poor-quality antimalarial drugs lead to drug resistance and inadequate treatment, which pose an urgent threat to vulnerable populations and jeopardise progress and investments in combating malaria. Emergence of artemisinin resistance or tolerance in Plasmodium falciparum on the Thailand-Cambodia border makes protection of the effectiveness of the drug supply imperative. We reviewed published and unpublished studies reporting chemical analyses and assessments of packaging of antimalarial drugs. Of 1437 samples of drugs in five classes from seven countries in southeast Asia, 497 (35%) failed chemical analysis, 423 (46%) of 919 failed packaging analysis, and 450 (36%) of 1260 were classified as falsified. In 21 surveys of drugs from six classes from 21 countries in sub-Saharan Africa, 796 (35%) of 2297 failed chemical analysis, 28 (36%) of 77 failed packaging analysis, and 79 (20%) of 389 were classified as falsified. Data were insufficient to identify the frequency of substandard (products resulting from poor manufacturing) antimalarial drugs, and packaging analysis data were scarce. Concurrent interventions and a multifaceted approach are needed to define and eliminate criminal production, distribution, and poor manufacturing of antimalarial drugs. Empowering of national medicine regulatory authorities to protect the global drug supply is more important than ever. Hide abstract

Cheeseman IH, Miller BA, Nair S, Nkhoma S, Tan A, Tan JC, Al Saai S, Phyo AP et al. 2012. A major genome region underlying artemisinin resistance in malaria. Science, 336 (6077), pp. 79-82. Read abstract | Read more

Evolving resistance to artemisinin-based compounds threatens to derail attempts to control malaria. Resistance has been confirmed in western Cambodia and has recently emerged in western Thailand, but is absent from neighboring Laos. Artemisinin resistance results in reduced parasite clearance rates (CRs) after treatment. We used a two-phase strategy to identify genome region(s) underlying this ongoing selective event. Geographical differentiation and haplotype structure at 6969 polymorphic single-nucleotide polymorphisms (SNPs) in 91 parasites from Cambodia, Thailand, and Laos identified 33 genome regions under strong selection. We screened SNPs and microsatellites within these regions in 715 parasites from Thailand, identifying a selective sweep on chromosome 13 that shows strong association (P = 10(-6) to 10(-12)) with slow CRs, illustrating the efficacy of targeted association for identifying the genetic basis of adaptive traits. Hide abstract

Kernif T, Socolovschi C, Wells K, Lakim MB, Inthalad S, Slesak G, Boudebouch N, Beaucournu JC, Newton PN, Raoult D, Parola P. 2012. Bartonella and Rickettsia in arthropods from the Lao PDR and from Borneo, Malaysia. Comp Immunol Microbiol Infect Dis, 35 (1), pp. 51-57. Read abstract | Read more

Rickettsioses and bartonelloses are arthropod-borne diseases of mammals with widespread geographical distributions. Yet their occurrence in specific regions, their association with different vectors and hosts and the infection rate of arthropod-vectors with these agents remain poorly studied in South-east Asia. We conducted entomological field surveys in the Lao PDR (Laos) and Borneo, Malaysia by surveying fleas, ticks, and lice from domestic dogs and collected additional samples from domestic cows and pigs in Laos. Rickettsia felis was detected by real-time PCR with similar overall flea infection rate in Laos (76.6%, 69/90) and Borneo (74.4%, 268/360). Both of the encountered flea vectors Ctenocephalides orientis and Ctenocephalides felis felis were infected with R. felis. The degrees of similarity of partial gltA and ompA genes with recognized species indicate the rickettsia detected in two Boophilus spp. ticks collected from a cow in Laos may be a new species. Isolation and further characterization will be necessary to specify it as a new species. Bartonella clarridgeiae was detected in 3/90 (3.3%) and 2/360 (0.6%) of examined fleas from Laos and Borneo, respectively. Two fleas collected in Laos and one flea collected in Borneo were co-infected with both R. felis and B. clarridgeiae. Further investigations are needed in order to isolate these agents and to determine their epidemiology and aetiological role in unknown fever in patients from these areas. Hide abstract

Paris DH, Phetsouvanh R, Tanganuchitcharnchai A, Jones M, Jenjaroen K, Vongsouvath M, Ferguson DP, Blacksell SD, Newton PN, Day NP, Turner GD. 2012. Orientia tsutsugamushi in human scrub typhus eschars shows tropism for dendritic cells and monocytes rather than endothelium. PLoS Negl Trop Dis, 6 (1), pp. e1466. Read abstract | Read more

Scrub typhus is a common and underdiagnosed cause of febrile illness in Southeast Asia, caused by infection with Orientia tsutsugamushi. Inoculation of the organism at a cutaneous mite bite site commonly results in formation of a localized pathological skin reaction termed an eschar. The site of development of the obligate intracellular bacteria within the eschar and the mechanisms of dissemination to cause systemic infection are unclear. Previous postmortem and in vitro reports demonstrated infection of endothelial cells, but recent pathophysiological investigations of typhus patients using surrogate markers of endothelial cell and leucocyte activation indicated a more prevalent host leucocyte than endothelial cell response in vivo. We therefore examined eschar skin biopsies from patients with scrub typhus to determine and characterize the phenotypes of host cells in vivo with intracellular infection by O. tsutsugamushi, using histology, immunohistochemistry, double immunofluorescence confocal laser scanning microscopy and electron microscopy. Immunophenotyping of host leucocytes infected with O. tsutsugamushi showed a tropism for host monocytes and dendritic cells, which were spatially related to different histological zones of the eschar. Infected leucocyte subsets were characterized by expression of HLADR+, with an "inflammatory" monocyte phenotype of CD14/LSP-1/CD68 positive or dendritic cell phenotype of CD1a/DCSIGN/S100/FXIIIa and CD163 positive staining, or occasional CD3 positive T-cells. Endothelial cell infection was rare, and histology did not indicate a widespread inflammatory vasculitis as the cause of the eschar. Infection of dendritic cells and activated inflammatory monocytes offers a potential route for dissemination of O. tsutsugamushi from the initial eschar site. This newly described cellular tropism for O. tsutsugamushi may influence its interaction with local host immune responses. Hide abstract

Rattanavong S, Vongthongchit S, Bounphamala K, Vongphakdy P, Gubler J, Mayxay M, Phetsouvanh R, Elliott I et al. 2012. Actinomycetoma in SE Asia: the first case from Laos and a review of the literature. BMC Infect Dis, 12 (1), pp. 349. Read abstract | Read more

Mycetoma is a chronic, localized, slowly progressing infection of the cutaneous and subcutaneous tissues caused either by fungi (eumycetoma or implantation mycosis) or by aerobic actinomycetes (actinomycetoma). It is acquired by traumatic implantation, most commonly in the tropics and subtropics, especially in rural agricultural communities. Although well recognized elsewhere in Asia, it has not been reported from the Lao People's Democratic Republic (Laos). Hide abstract

Attaran A, Barry D, Basheer S, Bate R, Benton D, Chauvin J, Garrett L, Kickbusch I et al. 2012. How to achieve international action on falsified and substandard medicines. BMJ, 345 (nov13 22), pp. e7381. | Read more

Paris DH, Nawtaisong P, Blacksell SD, Lee SJ, Dondorp AM, Day NPJ, Newton PN, Chansamouth V et al. 2012. Coagulation and inflammation in scrub typhus and murine typhus-a prospective comparative study from Laos Clinical Microbiology and Infection, 18 (12), pp. 1221-1228. Read abstract | Read more

Scrub typhus (caused by Orientia tsutsugamushi) and murine typhus (caused by Rickettsia typhi) cause up to 28% of febrile episodes in Thailand and Laos. The current understanding of coagulation and inflammation in the pathogenesis of these clinically very similar vasculotropic diseases is limited. This study compared human in vivo changes in 15 coagulation, inflammation and endothelial activation markers in prospectively collected admission and follow-up samples of 121 patients (55 scrub typhus, 55 murine typhus, and 11 typhus-like illness) and 51 healthy controls from Laos. As compared with controls, all but one of the markers assessed were significantly affected in typhus patients; however, the activation patterns differed significantly between scrub and murine typhus patients. The levels of markers of coagulation activation and all inflammatory cytokines, except for interleukin-12, were significantly higher in patients with scrub typhus than in those with murine typhus. In patients with murine typhus, however, the levels of endothelium-derived markers were significantly higher. Anticoagulant factors were inhibited in both typhus patient groups. This is the first study demonstrating that, in scrub typhus, in vivo coagulation activation is prominent and is related to a strong proinflammatory response, whereas in murine typhus, changes in coagulant and fibrinolytic pathways are suggestive of endothelial cell perturbation. These data suggest that, although late-stage endothelial infection is common in both diseases, the in vivo pathogenic mechanisms of R. typhi and O. tsutsugamushi could differ in the early phase of infection and may contribute to disease differentiation. © 2011 The Authors. Clinical Microbiology and Infection © 2011 European Society of Clinical Microbiology and Infectious Diseases. Hide abstract

White LJ, Newton PN, Maude RJ, Pan-ngum W, Fried JR, Mayxay M, Maude RR, Day NP. 2012. Defining disease heterogeneity to guide the empirical treatment of febrile illness in resource poor settings. PLoS One, 7 (9), pp. e44545. Read abstract | Read more

Malaria incidence is in decline in many parts of SE Asia leading to a decreasing proportion of febrile illness that is attributable to malaria. However in the absence of rapid, affordable and accurate diagnostic tests, the non-malaria causes of these illnesses cannot be reliably identified. Studies on the aetiology of febrile illness have indicated that the causes are likely to vary by geographical location within countries (i.e. be spatially heterogeneous) and that national empirical treatment policies based on the aetiology measured in a single location could lead to inappropriate treatment. Hide abstract

Blacksell SD, Lee SJ, Chanthongthip A, Taojaikong T, Thongpaseuth S, Hübscher T, Newton PN. 2012. Short report: Comparison of performance of serum and plasma in panbio dengue and Japanese encephalitis virus enzyme-linked immunosorbent assays American Journal of Tropical Medicine and Hygiene, 87 (3), pp. 573-575. Read abstract | Read more

We examined the comparative performance of serum and plasma (in dipotassium EDTA) in Panbio Dengue enzyme-linked immunosorbent assays (ELISAs) for detection of non-structural protein 1 (NS1), IgM, and IgG, and a dengue/Japanese encephalitis virus (JEV) combination IgM ELISA in a prospective series of 201 patients with suspected dengue in Laos. Paired comparisons of medians from serum and plasma samples were not significantly different for Dengue IgM, and NS1 which had the highest number of discordant pairs (both 2%; P = 0.13 and P = 0.25, respectively). Comparison of qualitative final diagnostic interpretations for serum and plasma samples were not significantly different: only 1.5% (3 of 201 for Dengue/JEV IgM and Dengue IgG) and 2.0% (4 of 201; IgM and NS1) showed discordant pairs. These results demonstrate that plasma containing EDTA is suitable for use in these ELISAs. Copyright © 2012 by The American Society of Tropical Medicine and Hygiene. Hide abstract

Acestor N, Cooksey R, Newton PN, Ménard D, Guerin PJ, Nakagawa J, Christophel E, González IJ, Bell D. 2012. Mapping the aetiology of non-malarial febrile illness in Southeast Asia through a systematic review--terra incognita impairing treatment policies. PLoS One, 7 (9), pp. e44269. Read abstract | Read more

An increasing use of point of care diagnostic tests that exclude malaria, coupled with a declining malaria burden in many endemic countries, is highlighting the lack of ability of many health systems to manage other causes of febrile disease. A lack of knowledge of distribution of these pathogens, and a lack of screening and point-of-care diagnostics to identify them, prevents effective management of these generally treatable contributors to disease burden. While prospective data collection is vital, an untapped body of knowledge already exists in the published health literature. Hide abstract

Newton PN, Green MD, Mildenhall DC, Plançon A, Nettey H, Nyadong L, Hostetler DM, Swamidoss I et al. 2011. Poor quality vital anti-malarials in Africa - an urgent neglected public health priority. Malar J, 10 (1), pp. 352. Read abstract | Read more

Plasmodium falciparum malaria remains a major public health problem. A vital component of malaria control rests on the availability of good quality artemisinin-derivative based combination therapy (ACT) at the correct dose. However, there are increasing reports of poor quality anti-malarials in Africa. Hide abstract

Newton PN, Amin AA, Bird C, Passmore P, Dukes G, Tomson G, Simons B, Bate R, Guerin PJ, White NJ. 2011. The primacy of public health considerations in defining poor quality medicines. PLoS Med, 8 (12), pp. e1001139. | Read more

Paris DH, Chansamouth V, Nawtaisong P, Löwenberg EC, Phetsouvanh R, Blacksell SD, Lee SJ, Dondorp AM et al. 2012. Coagulation and inflammation in scrub typhus and murine typhus--a prospective comparative study from Laos. Clin Microbiol Infect, 18 (12), pp. 1221-1228. Read abstract | Read more

Scrub typhus (caused by Orientia tsutsugamushi) and murine typhus (caused by Rickettsia typhi) cause up to 28% of febrile episodes in Thailand and Laos. The current understanding of coagulation and inflammation in the pathogenesis of these clinically very similar vasculotropic diseases is limited. This study compared human in vivo changes in 15 coagulation, inflammation and endothelial activation markers in prospectively collected admission and follow-up samples of 121 patients (55 scrub typhus, 55 murine typhus, and 11 typhus-like illness) and 51 healthy controls from Laos. As compared with controls, all but one of the markers assessed were significantly affected in typhus patients; however, the activation patterns differed significantly between scrub and murine typhus patients. The levels of markers of coagulation activation and all inflammatory cytokines, except for interleukin-12, were significantly higher in patients with scrub typhus than in those with murine typhus. In patients with murine typhus, however, the levels of endothelium-derived markers were significantly higher. Anticoagulant factors were inhibited in both typhus patient groups. This is the first study demonstrating that, in scrub typhus, in vivo coagulation activation is prominent and is related to a strong proinflammatory response, whereas in murine typhus, changes in coagulant and fibrinolytic pathways are suggestive of endothelial cell perturbation. These data suggest that, although late-stage endothelial infection is common in both diseases, the in vivo pathogenic mechanisms of R. typhi and O. tsutsugamushi could differ in the early phase of infection and may contribute to disease differentiation. Hide abstract

Stoesser N, Crook DW, Moore CE, Phetsouvanh R, Chansamouth V, Newton PN, Jones N. 2012. Characteristics of CTX-M ESBL-producing Escherichia coli isolates from the Lao People's Democratic Republic, 2004-09. J Antimicrob Chemother, 67 (1), pp. 240-242. | Read more

Mok S, Imwong M, Mackinnon MJ, Sim J, Ramadoss R, Yi P, Mayxay M, Chotivanich K et al. 2011. Artemisinin resistance in Plasmodium falciparum is associated with an altered temporal pattern of transcription. BMC Genomics, 12 (1), pp. 391. Read abstract | Read more

Artemisinin resistance in Plasmodium falciparum malaria has emerged in Western Cambodia. This is a major threat to global plans to control and eliminate malaria as the artemisinins are a key component of antimalarial treatment throughout the world. To identify key features associated with the delayed parasite clearance phenotype, we employed DNA microarrays to profile the physiological gene expression pattern of the resistant isolates. Hide abstract

Khennavong M, Davone V, Vongsouvath M, Phetsouvanh R, Silisouk J, Rattana O, Mayxay M, Castonguay-Vanier J, Moore CE, Strobel M, Newton PN. 2011. Urine antibiotic activity in patients presenting to hospitals in Laos: implications for worsening antibiotic resistance. Am J Trop Med Hyg, 85 (2), pp. 295-302. Read abstract | Read more

Widespread use of antibiotics may be important in the spread of antimicrobial resistance. We estimated the proportion of Lao in- and outpatients who had taken antibiotics before medical consultation by detecting antibiotic activity in their urine added to lawns of Bacillus stearothermophilus, Escherichia coli, and Streptococcus pyogenes. In the retrospective (N = 2,058) and prospective studies (N = 1,153), 49.7% (95% confidence interval [CI] = 47.4-52.0) and 36.2% (95% CI = 33.4-38.9), respectively, of Vientiane patients had urinary antibiotic activity detected. The highest frequency of estimated antibiotic pre-treatment was found in patients recruited with suspected central nervous system infections and community-acquired septicemia (both 56.8%). In Vientiane, children had a higher frequency of estimated antibiotic pre-treatment than adults (60.0% versus 46.5%; P < 0.001). Antibiotic use based on patients histories was significantly less frequent than when estimated from urinary antibiotic activity (P < 0.0001). Hide abstract

Lubell Y, Staedke SG, Greenwood BM, Kamya MR, Molyneux M, Newton PN, Reyburn H, Snow RW et al. 2011. Likely health outcomes for untreated acute febrile illness in the tropics in decision and economic models; a Delphi survey. PLoS One, 6 (2), pp. e17439. Read abstract | Read more

Modelling is widely used to inform decisions about management of malaria and acute febrile illnesses. Most models depend on estimates of the probability that untreated patients with malaria or bacterial illnesses will progress to severe disease or death. However, data on these key parameters are lacking and assumptions are frequently made based on expert opinion. Widely diverse opinions can lead to conflicting outcomes in models they inform. Hide abstract

Khounnorath S, Chamberlain K, Taylor AM, Soukaloun D, Mayxay M, Lee SJ, Phengdy B, Luangxay K et al. 2011. Clinically unapparent infantile thiamin deficiency in Vientiane, Laos. PLoS Negl Trop Dis, 5 (2), pp. e969. Read abstract | Read more

Beriberi occurs in Vientiane, Lao PDR, among breastfed infants. Clinical disease may be the tip of an iceberg with subclinical thiamin deficiency contributing to other illnesses. Thiamin treatment could improve outcome. Hide abstract

Conlan JV, Sripa B, Attwood S, Newton PN. 2011. A review of parasitic zoonoses in a changing Southeast Asia. Vet Parasitol, 182 (1), pp. 22-40. Read abstract | Read more

Parasitic zoonoses are common and widely distributed in the Southeast Asian region. However, the interactions between parasites, hosts and vectors are influenced by environmental, socio-cultural and livestock production changes that impact on the distribution, prevalence and severity of disease. In this review we provide an update on new knowledge in the context of ongoing changes for the food-borne pig associated zoonoses Taenia solium and Trichinella spp., the food-borne trematodes Opisthorchis viverrini and Clonorchis sinensis, the water-borne trematodes Schistosoma spp., the vector-borne zoonotic protozoa Plasmodium knowlesi and Leishmania spp. and the soil-borne zoonotic hookworm Ancylostoma ceylanicum. These various changes need to be considered when assessing or developing regional control programs or devising new research initiatives in a changing SE Asia. Hide abstract

Peacock S, Newton P. 2011. In Response American Journal of Tropical Medicine and Hygiene, 84 (2), pp. 359-359. | Read more

Slesak G, Inthalad S, Strobel M, Marschal M, Hall M, Newton PN. 2011. Chromoblastomycosis after a leech bite complicated by myiasis: a case report. BMC Infect Dis, 11 (1), pp. 14. Read abstract | Read more

Chromoblastomycosis is a chronic mycotic infection, most common in the tropics and subtropics, following traumatic fungal implantation. Hide abstract

Soukaloun D, Lee SJ, Chamberlain K, Taylor AM, Mayxay M, Sisouk K, Soumphonphakdy B, Latsavong K et al. 2011. Erythrocyte transketolase activity, markers of cardiac dysfunction and the diagnosis of infantile beriberi. PLoS Negl Trop Dis, 5 (2), pp. e971. Read abstract | Read more

Infantile beriberi is a potentially lethal manifestation of thiamin deficiency, associated with traditional post-partum maternal food avoidance, which persists in the Lao PDR (Laos). There are few data on biochemical markers of infantile thiamin deficiency or indices of cardiac dysfunction as potential surrogate markers. Hide abstract

Slesak G, Mounlaphome K, Inthalad S, Phoutsavath O, Mayxay M, Newton PN. 2011. Bowel obstruction from wild bananas: a neglected health problem in Laos. Trop Doct, 41 (2), pp. 85-90. Read abstract | Read more

We investigated the significance and risk factors of bowel obstruction caused by the consumption of wild bananas (BOWB) in Laos. Of six patients with BOWB in Luang Namtha, North Laos, five required enterotomy for phytobezoars. All had eaten wild banana (WB) seeds. Of 227 other patients/relatives: 91.2% had eaten WB; 46.3% had also eaten the seeds and 45.4% knew of complications resulting from eating WB; 42.3% were aware of the complications of ingesting the seeds (constipation [37.9%], appendicitis/abdominal pain/vomiting [2.6% each] and bloated stomach/death [1.3% each]). Middle/highland Lao ethnicity was associated with WB and seed consumption (odds ratio [OR] 9.91 and 2.33), male sex with WB consumption and unawareness (OR 4.31 and 1.78). At all surgically-equipped hospitals in Laos, 33/44 doctors knew of BOWB, describing patients as young adults (16/30), male (24/30) and from middleland Lao (18/30). Countrywide, 46/48 patients with BOWB required laparotomy in 2009 (incidence 0.8/100,000). All consumed WB seeds. BOWB is widespread in Laos, especially among young middleland Lao men consuming WB seeds on an empty stomach. Hide abstract

Mayxay M, Keomany S, Khanthavong M, Souvannasing P, Stepniewska K, Khomthilath T, Keola S, Pongvongsa T et al. 2010. A phase III, randomized, non-inferiority trial to assess the efficacy and safety of dihydroartemisinin-piperaquine in comparison with artesunate-mefloquine in patients with uncomplicated Plasmodium falciparum malaria in southern Laos. Am J Trop Med Hyg, 83 (6), pp. 1221-1229. Read abstract | Read more

We conducted an open, randomized clinical trial of oral dihydroartemisinin-piperaquine (DP) versus artesunate-mefloquine (AM) in 300 patients in Laos with uncomplicated Plasmodium falciparum malaria as part of a multicentre study in Asia. Survival analysis and adjustment for re-infection showed that the 63-day cure rates (95% confidence interval [CI]) were 100% for AM and 99.5% (96.4-99.8%) for DP. The 63-day cure rates per protocol were 99% (97 of 98) for AM and 99.5% (196 of 197) for DP (P = 0.55). The difference (AM minus DP) in cure rates (95% CI) was -0.5% (-5.1 to 2.0%), which is within the 5% non-inferiority margin. The median fever and parasite clearance times were also similar for AM and DP. The proportion of patients with at least one recorded potential adverse event was significantly higher in the AM group (38 of 87, 44%) than in the DP group (57 of 182, 31%) (relative risk = 0.6, 95% CI = 0.4-0.9; P = 0.04). Dihydroartemisinin-piperaquine is not inferior to AM in the treatment of uncomplicated P. falciparum malaria in Laos and is associated with fewer adverse effects. The results of this study were similar to those of the larger multicentre study. Hide abstract

Rattanavong S, Wuthiekanun V, Langla S, Amornchai P, Sirisouk J, Phetsouvanh R, Moore CE, Peacock SJ, Buisson Y, Newton PN. 2011. Randomized soil survey of the distribution of Burkholderia pseudomallei in rice fields in Laos. Appl Environ Microbiol, 77 (2), pp. 532-536. Read abstract | Read more

Melioidosis is a major cause of morbidity and mortality in Southeast Asia, where the causative organism (Burkholderia pseudomallei) is present in the soil. In the Lao People's Democratic Republic (Laos), B. pseudomallei is a significant cause of sepsis around the capital, Vientiane, and has been isolated in soil near the city, adjacent to the Mekong River. We explored whether B. pseudomallei occurs in Lao soil distant from the Mekong River, drawing three axes across northwest, northeast, and southern Laos to create nine sampling areas in six provinces. Within each sampling area, a random rice field site containing a grid of 100 sampling points each 5 m apart was selected. Soil was obtained from a depth of 30 cm and cultured for B. pseudomallei. Four of nine sites (44%) were positive for B. pseudomallei, including all three sites in Saravane Province, southern Laos. The highest isolation frequency was in east Saravane, where 94% of soil samples were B. pseudomallei positive with a geometric mean concentration of 464 CFU/g soil (95% confidence interval, 372 to 579 CFU/g soil; range, 25 to 10,850 CFU/g soil). At one site in northwest Laos (Luangnamtha), only one sample (1%) was positive for B. pseudomallei, at a concentration of 80 CFU/g soil. Therefore, B. pseudomallei occurs in Lao soils beyond the immediate vicinity of the Mekong River, alerting physicians to the likelihood of melioidosis in these areas. Further studies are needed to investigate potential climatic, soil, and biological determinants of this heterogeneity. Hide abstract

Mayxay M, Phetsouvanh R, Moore CE, Chansamouth V, Vongsouvath M, Sisouphone S, Vongphachanh P, Thaojaikong T et al. 2011. Predictive diagnostic value of the tourniquet test for the diagnosis of dengue infection in adults. Trop Med Int Health, 16 (1), pp. 127-133. Read abstract | Read more

To examine the accuracy of the admission tourniquet test in the diagnosis of dengue infection among Lao adults. Hide abstract

Moore CE, Sengduangphachanh A, Thaojaikong T, Sirisouk J, Foster D, Phetsouvanh R, McGee L, Crook DW, Newton PN, Peacock SJ. 2010. Enhanced determination of Streptococcus pneumoniae serotypes associated with invasive disease in Laos by using a real-time polymerase chain reaction serotyping assay with cerebrospinal fluid. Am J Trop Med Hyg, 83 (3), pp. 451-457. Read abstract | Read more

A prospective hospital-based study was undertaken to define the incidence of invasive pneumococcal disease (IPD) and circulating serotypes in Laos. Of 10,799 patients with hemocultures and 353 patients with cerebrospinal fluid samples, 0.21% and 5.4%, respectively, were positive for Streptococcus pneumoniae, giving a total of 35 IPD patients. We developed a real-time polymerase chain reaction to detect serotypes represented in the 13-valent pneumococcal vaccine. A blinded evaluation comparing serotype as defined by the Quellung reaction versus the polymerase chain reaction demonstrated 100% concordance. The most frequent serotype (n = 33 patients) was 1 (n = 6), followed by serotypes 5, 6A/B/C, 14, and 23F. Serotypes represented in the 7-valent polysaccharide-protein conjugate vaccine (PCV-7) infected 39% of patients, with 73% coverage for the PCV-10 and PCV-13 vaccines. Although the sample size is small, these data suggest that the PCV-7 vaccine may have relatively low efficacy in Laos. Further studies are urgently needed to guide pneumococcal vaccine policy in Laos. Hide abstract

Blacksell SD, Jenjaroen K, Phetsouvanh R, Tanganuchitcharnchai A, Phouminh P, Phongmany S, Day NP, Newton PN. 2010. Accuracy of rapid IgM-based immunochromatographic and immunoblot assays for diagnosis of acute scrub typhus and murine typhus infections in Laos. Am J Trop Med Hyg, 83 (2), pp. 365-369. Read abstract | Read more

We studied the diagnostic accuracy of a rapid immunochromatographic test (ICT) for detection of IgM against scrub typhus (ST ICT) and an immunoblot test for the detection of IgM against murine typhus (MT IBT) by using admission serum samples from 1,030 febrile patients in Laos. Sensitivity and specificity for the ST ICT determined by using the diagnostic criteria of a four-fold increase in IgM against Orientia tsutsugamushi between paired samples were 23.8% (95% confidence interval [CI] = 15.9-33.3%) and 86.2% (95% CI = 84.1-88.6%), respectively. Sensitivity and specificity for the ST ICT determined by using an admission IgM titer > or = 1:400 were 39.1% (95% CI = 34.1-44.2%) and 99.5% (95% CI = 98.7-99.9%), respectively. Sensitivity and specificity for the MT IBT determined by using the criteria of a four-fold increase in IgM against Rickettsia typhi between paired serum samples were 61.2% (95% CI = 53.7-68.3%) and 86.5% (95% CI = 84.1-88.8%), respectively. Sensitivity and specificity for the MT IBT determined by using an admission IgM titer > or = 1:400 were 54.6% (95% CI = 49.1-60.0%) and 94.1% (95% CI = 92.0-95.7%), respectively. Both assays had relatively good specificity but low sensitivity and thus have limited utility for admission diagnosis. Hide abstract

Valecha N, Phyo AP, Mayxay M, Newton PN, Krudsood S, Keomany S, Khanthavong M, Pongvongsa T et al. 2010. An open-label, randomised study of dihydroartemisinin-piperaquine versus artesunate-mefloquine for falciparum malaria in Asia. PLoS One, 5 (7), pp. e11880. Read abstract | Read more

The artemisinin-based combination treatment (ACT) of dihydroartemisinin (DHA) and piperaquine (PQP) is a promising novel anti-malarial drug effective against multi-drug resistant falciparum malaria. The aim of this study was to show non-inferiority of DHA/PQP vs. artesunate-mefloquine (AS+MQ) in Asia. Hide abstract

Syhavong B, Rasachack B, Smythe L, Rolain JM, Roque-Afonso AM, Jenjaroen K, Soukkhaserm V, Phongmany S et al. 2010. The infective causes of hepatitis and jaundice amongst hospitalised patients in Vientiane, Laos. Trans R Soc Trop Med Hyg, 104 (7), pp. 475-483. Read abstract | Read more

There is little information on the diverse infectious causes of jaundice and hepatitis in the Asiatic tropics. Serology (hepatitis A, B, C and E, leptospirosis, dengue, rickettsia), antigen tests (dengue), PCR assays (hepatitis A, C and E) and blood cultures (septicaemia) were performed on samples from 392 patients admitted with jaundice or raised transaminases (> or =x3) to Mahosot Hospital, Vientiane, Laos over 3 years. Conservative definitions suggested diagnoses of dengue (8.4%), rickettsioses (7.3%), leptospirosis (6.8%), hepatitis B (4.9%), hepatitis C (4.9%), community-acquired septicaemia (3.3%) and hepatitis E (1.6%). Although anti-hepatitis A virus (HAV) IgM antibody results suggested that 35.8% of patients had acute HAV infections, anti-HAV IgG antibody avidity and HAV PCR suggested that 82% had polyclonal activation and not acute HAV infections. Scrub typhus, murine typhus or leptospirosis were present in 12.8% of patients and were associated with meningism and relatively low AST and ALT elevation. These patients would be expected to respond to empirical doxycycline therapy which, in the absence of virological diagnosis and treatment, may be an appropriate cost-effective intervention in Lao patients with jaundice/hepatitis. Hide abstract

Tantibhedhyangkul W, Angelakis E, Tongyoo N, Newton PN, Moore CE, Phetsouvanh R, Raoult D, Rolain JM. 2010. Intrinsic fluoroquinolone resistance in Orientia tsutsugamushi. Int J Antimicrob Agents, 35 (4), pp. 338-341. Read abstract | Read more

Scrub typhus is a public health concern for a population of over a billion humans, with an estimated incidence of one million cases/year in endemic areas. Although doxycycline remains the standard therapy, fluoroquinolones have been used successfully in a few patients. However, there is also clinical evidence that fluoroquinolones are ineffective in the treatment of scrub typhus. To clarify this matter, we determined the in vitro susceptibility of Orientia tsutsugamushi strain Kato to ciprofloxacin and ofloxacin and sequenced the quinolone resistance-determining region (QRDR) of the gyrA gene, the target of fluoroquinolones, of 18 fresh isolates from the Lao PDR. Orientia tsutsugamushi strain Kato was resistant to ciprofloxacin and ofloxacin in vitro (minimum inhibitory concentration=8 microg/mL). All sequences obtained, including those from the two available genomes of O. tsutsugamushi (strains Boryong and Ikeda), had a Ser83Leu mutation in their QRDR domain that is known to be associated with fluoroquinolone resistance. These findings re-emphasise the usefulness of in silico analysis for the prediction of antibiotic resistance and suggest that fluoroquinolones should not be used in the treatment of scrub typhus. Hide abstract

Koh GC, Maude RJ, Paris DH, Newton PN, Blacksell SD. 2010. Diagnosis of scrub typhus. Am J Trop Med Hyg, 82 (3), pp. 368-370. Read abstract | Read more

Scrub typhus is transmitted by trombiculid mites and is endemic to East and Southeast Asia and Northern Australia. The clinical syndrome classically consists of a fever, rash, and eschar, but scrub typhus also commonly presents as an undifferentiated fever that requires laboratory confirmation of the diagnosis, usually by indirect fluorescent antibody (IFA) assay. We discuss the limitations of IFA, debate the value of other methods based on antigen detection and nucleic acid amplification, and outline recommendations for future study. Hide abstract

Stepniewska K, Ashley E, Lee SJ, Anstey N, Barnes KI, Binh TQ, D'Alessandro U, Day NP et al. 2010. In vivo parasitological measures of artemisinin susceptibility. J Infect Dis, 201 (4), pp. 570-579. Read abstract | Read more

Parasite clearance data from 18,699 patients with falciparum malaria treated with an artemisinin derivative in areas of low (n=14,539), moderate (n=2077), and high (n=2083) levels of malaria transmission across the world were analyzed to determine the factors that affect clearance rates and identify a simple in vivo screening measure for artemisinin resistance. The main factor affecting parasite clearance time was parasite density on admission. Clearance rates were faster in high-transmission settings and with more effective partner drugs in artemisinin-based combination treatments (ACTs). The result of the malaria blood smear on day 3 (72 h) was a good predictor of subsequent treatment failure and provides a simple screening measure for artemisinin resistance. Artemisinin resistance is highly unlikely if the proportion of patients with parasite densities of <100,000 parasites/microL given the currently recommended 3-day ACT who have a positive smear result on day 3 is <3%; that is, for n patients the observed number with a positive smear result on day 3 does not exceed (n + 60)/24. Hide abstract

Newton PN, Green MD, Fernández FM. 2010. Impact of poor-quality medicines in the 'developing' world. Trends Pharmacol Sci, 31 (3), pp. 99-101. Read abstract | Read more

Since our ancestors began trading several millennia ago, counterfeit and substandard medicines have been a recurring problem, with history punctuated by crises in the supply of anti-microbials, such as fake cinchona bark in the 1600s and fake quinine in the 1800s. Unfortunately this problem persists, in particular afflicting unsuspecting patients in 'developing' countries. Poor-quality drugs are a vital (but neglected) public health problem. They contribute to a 'crevasse' between the enormous effort in therapeutic research and policy decisions and implementation of good-quality medicines. Hide abstract

Kaur H, Green MD, Hostetler DM, Fernández FM, Newton PN. 2010. Antimalarial drug quality: methods to detect suspect drugs Therapy, 7 (1), pp. 49-57. Read abstract | Read more

Malaria is a major public health problem in the endemic countries of Africa, Asia and Latin America. Poor quality antimalarials are of major, but neglected, concern in the control of Plasmodium falciparum malaria. They cause treatment failure and economic loss, and engender drug resistance and loss of confidence in health systems. The emergence of resistance to the artemisinin derivatives in Asia bodes ill for malaria control in Africa, and strenuous efforts are needed to improve the quality of the world's supply of antimalarials. This article reviews the problem and discusses methods available to determine the quality of antimalarials. © 2010 Future Medicine Ltd. Hide abstract

Vallée J, Thaojaikong T, Moore CE, Phetsouvanh R, Richards AL, Souris M, Fournet F, Salem G, Gonzalez JP, Newton PN. 2010. Contrasting spatial distribution and risk factors for past infection with scrub typhus and murine typhus in Vientiane City, Lao PDR. PLoS Negl Trop Dis, 4 (12), pp. e909. Read abstract | Read more

The aetiological diagnostic of fevers in Laos remains difficult due to limited laboratory diagnostic facilities. However, it has recently become apparent that both scrub and murine typhus are common causes of previous undiagnosed fever. Epidemiological data suggests that scrub typhus would be more common in rural areas and murine typhus in urban areas, but there is very little recent information on factors involved in scrub and murine typhus transmission, especially where they are sympatric - as is the case in Vientiane, the capital of the Lao PDR. Hide abstract

Fernandez FM, Hostetler D, Powell K, Kaur H, Green MD, Mildenhall DC, Newton PN. 2011. Poor quality drugs: grand challenges in high throughput detection, countrywide sampling, and forensics in developing countries. Analyst, 136 (15), pp. 3073-3082. Read abstract | Read more

Throughout history, poor quality medicines have been a persistent problem, with periodical crises in the supply of antimicrobials, such as fake cinchona bark in the 1600s and fake quinine in the 1800s. Regrettably, this problem seems to have grown in the last decade, especially afflicting unsuspecting patients and those seeking medicines via on-line pharmacies. Here we discuss some of the challenges related to the fight against poor quality drugs, and counterfeits in particular, with an emphasis on the analytical tools available, their relative performance, and the necessary workflows needed for distinguishing between genuine, substandard, degraded and counterfeit medicines. Hide abstract

Blacksell SD, Jenjaroen K, Phetsouvanh R, Wuthiekanun V, Day NP, Newton PN, Ching WM. 2010. Accuracy of AccessBio Immunoglobulin M and Total Antibody Rapid Immunochromatographic Assays for the Diagnosis of Acute Scrub Typhus Infection. Clin Vaccine Immunol, 17 (2), pp. 263-266. Read abstract | Read more

Using archived samples, we assessed the diagnostic capacity of a rapid immunochromatographic test (ICT) for the detection of Orientia tsutsugamushi IgM and total antibodies to aid with the diagnosis of acute scrub typhus infection in febrile patients in Laos. The sensitivity and the specificity of the ICT for the detection of IgM were 96.8% (121/125 samples; 95% confidence interval [CI], 92.1 to 99.1%) and 93.3% (98/105 samples; 95% CI, 86.7 to 97.3%), respectively. For the detection of total antibodies, the sensitivity was 97.6% (122/125 samples; 95% CI, 93.1 to 99.5%), but the specificity was much lower, at 71.4% (75/105 samples; 95% CI, 61.8 to 79.8%). Hide abstract

Angelakis E, Khamphoukeo K, Grice D, Newton PN, Roux V, Aplin K, Raoult D, Rolain JM. 2009. Molecular detection of Bartonella species in rodents from the Lao PDR. Clin Microbiol Infect, 15 Suppl 2 (SUPPL. 2), pp. 95-97. | Read more

Newton PN, Rolain JM, Rasachak B, Mayxay M, Vathanatham K, Seng P, Phetsouvanh R, Thammavong T et al. 2009. Sennetsu neorickettsiosis: a probable fish-borne cause of fever rediscovered in Laos. Am J Trop Med Hyg, 81 (2), pp. 190-194. Read abstract

Neorickettsia sennetsu has been described from Japan and Malaysia, causing a largely forgotten infectious mononucleosis-like disease. Because it is believed to be contracted from eating raw fish, frequently consumed in the Lao PDR, we looked for evidence of N. sennetsu among Lao patients and fish. A buffy coat from 1 of 91 patients with undifferentiated fever was positive by 16S rRNA amplification and sequencing and real-time polymerase chain reactions (PCR) targeting two N. sennetsu genes. Lao blood donors and patients with fever, hepatitis, or jaundice (N = 1,132) had a high prevalence (17%) of immunofluorescence assay IgG anti-N. sennetsu antibodies compared with 4% and 0% from febrile patients (N = 848) in Thailand and Malaysia, respectively. We found N. sennetsu DNA by PCR, for the first time, in a fish (Anabas testudineus). These data suggest that sennetsu may be an under-recognized cause of fever and are consistent with the hypothesis that it may be contracted from eating raw fish. Hide abstract

Sengaloundeth S, Green MD, Fernández FM, Manolin O, Phommavong K, Insixiengmay V, Hampton CY, Nyadong L et al. 2009. A stratified random survey of the proportion of poor quality oral artesunate sold at medicine outlets in the Lao PDR - implications for therapeutic failure and drug resistance. Malar J, 8 (1), pp. 172. Read abstract | Read more

Counterfeit oral artesunate has been a major public health problem in mainland SE Asia, impeding malaria control. A countrywide stratified random survey was performed to determine the availability and quality of oral artesunate in pharmacies and outlets (shops selling medicines) in the Lao PDR (Laos). Hide abstract

Phetsouvanh R, Blacksell SD, Jenjaroen K, Day NP, Newton PN. 2009. Comparison of indirect immunofluorescence assays for diagnosis of scrub typhus and murine typhus using venous blood and finger prick filter paper blood spots. Am J Trop Med Hyg, 80 (5), pp. 837-840. Read abstract

We performed indirect immunofluorescence assays (IFAs) to compare levels of IgM and IgG antibodies to Orientia tsutsugamushi and Rickettsia typhi in admission-phase serum samples and filter paper blood spots (assayed immediately and stored at 5.4 degrees C and 29 degrees C for 30 days) collected on the same day from 53 adults with suspected scrub typhus and murine typhus admitted to Mahosot Hospital Vientiane, Lao People's Democratic Republic. The sensitivities and specificities of admission-phase filter paper blood spots in comparison to paired sera were between 91% and 95% and 87% and 100%, respectively, for the diagnosis of scrub typhus and murine typhus. The classification of patients as having or not having typhus did not significantly differ after storage of the blood spots for 30 days (P > 0.4) at 5.4 degrees C and 29 degrees C. Because filter paper blood samples do not require sophisticated and expensive storage and transport, they may be an appropriate specimen collection technique for the diagnosis of rickettsial disease in the rural tropics. Hide abstract

Newton PN, Lee SJ, Goodman C, Fernández FM, Yeung S, Phanouvong S, Kaur H, Amin AA et al. 2009. Guidelines for field surveys of the quality of medicines: a proposal. PLoS Med, 6 (3), pp. e52. | Read more

Barennes H, Simmala C, Odermatt P, Thaybouavone T, Vallee J, Martinez-Aussel B, Newton PN, Strobel M. 2009. Postpartum traditions and nutrition practices among urban Lao women and their infants in Vientiane, Lao PDR (vol 63, pg 323, 2009) EUROPEAN JOURNAL OF CLINICAL NUTRITION, 63 (3), pp. 450-450. | Read more

Charunwatthana P, Abul Faiz M, Ruangveerayut R, Maude RJ, Rahman MR, Roberts LJ, Moore K, Bin Yunus E et al. 2009. N-acetylcysteine as adjunctive treatment in severe malaria: a randomized, double-blinded placebo-controlled clinical trial. Crit Care Med, 37 (2), pp. 516-522. Read abstract | Read more

Markers of oxidative stress are reported to be increased in severe malaria. It has been suggested that the antioxidant N-acetylcysteine (NAC) may be beneficial in treatment. We studied the efficacy and safety of parenteral NAC as an adjunct to artesunate treatment of severe falciparum malaria. Hide abstract

Pybus OG, Barnes E, Taggart R, Lemey P, Markov PV, Rasachak B, Syhavong B, Phetsouvanah R et al. 2009. Genetic history of hepatitis C virus in East Asia. J Virol, 83 (2), pp. 1071-1082. Read abstract | Read more

The hepatitis C virus (HCV), which currently infects an estimated 3% of people worldwide, has been present in some human populations for several centuries, notably HCV genotypes 1 and 2 in West Africa and genotype 6 in Southeast Asia. Here we use newly developed methods of sequence analysis to conduct the first comprehensive investigation of the epidemic and evolutionary history of HCV in Asia. Our analysis includes new HCV core (n = 16) and NS5B (n = 14) gene sequences, obtained from serum samples of jaundiced patients from Laos. These exceptionally diverse isolates were analyzed in conjunction with all available reference strains using phylogenetic and Bayesian coalescent methods. We performed statistical tests of phylogeographic structure and applied a recently developed "relaxed molecular clock" approach to HCV for the first time, which indicated an unexpectedly high degree of rate variation. Our results reveal a >1,000-year-long development of genotype 6 in Asia, characterized by substantial phylogeographic structure and two distinct phases of epidemic history, before and during the 20th century. We conclude that HCV lineages representing preexisting and spatially restricted strains were involved in multiple, independent local epidemics during the 20th century. Our analysis explains the generation and maintenance of HCV diversity in Asia and could provide a template for further investigations of HCV spread in other regions. Hide abstract

Zwang J, Ashley EA, Nosten F, Singhasivanon P, Stepniewska K, White NJ, Mayxay M, Smithuis F et al. 2009. Safety and efficacy of dihydroartemisinin-piperaquine in falciparum malaria: A prospective multi-centre individual patient data analysis PLoS ONE, 4 (7), Read abstract | Read more

Background: The fixed dose antimalarial combination of dihydroartemisinin-piperaquine (DP) is a promising new artemisinin-based combination therapy (ACT). We present an individual patient data analysis of efficacy and tolerability in acute uncomplicated falciparum malaria, from seven published randomized clinical trials conducted in Africa and South East Asia using a predefined in-vivo protocol. Comparator drugs were mefloquine-artesunate (MAS3) in Thailand, Myanmar, Laos and Cambodia; artemether-lumefantrine in Uganda; and amodiaquine+sulfadoxine-pyrimethamine and artesunate+amodiaquine in Rwanda. Methods and Findings: In total 3,547 patients were enrolled: 1,814 patients (32% children under five years) received DP and 1,733 received a comparator antimalarial at 12 different sites and were followed for 28-63 days. There was no significant heterogeneity between trials. DP was well tolerated with 1.7% early vomiting. There were less adverse events with DP in children and adults compared to MAS3 except for diarrhea; ORs (95%CI) 2.74 (2.13 to 3.51) and 3.11 (2.31 to 4.18), respectively. DP treatment resulted in a rapid clearance of fever and parasitaemia. The PCR genotype corrected efficacy at Day 28 of DP assessed by survival analysis was 98.7% (95%CI 97.6-99.8). DP was superior to the comparator drugs in protecting against both P.falciparum recurrence and recrudescence (P = 0.001, weighted by site). There was no difference between DP and MAS3 in treating P. vivax co-infections and in suppressing the first relapse (median interval to P. vivax recurrence: 6 weeks). Children under 5 y were at higher risk of recurrence for both infections. The proportion of patients developing gametocytaemia (P = 0.002, weighted by site) and the subsequent gametocyte carriage rates were higher with DP (11/1000 person gametocyte week, PGW) than MAS3 (6/ 1000 PGW, P = 0.001, weighted by site). Conclusions: DP proved a safe, well tolerated, and highly effective treatment of P.falciparum malaria in Asia and Africa, but the effect on gametocyte carriage was inferior to that of MAS3. © 2009 Zwang et al. Hide abstract

Barennes H, Simmala C, Odermatt P, Thaybouavone T, Vallee J, Martinez-Aussel B, Newton PN, Strobel M. 2009. Erratum: Postpartum traditions and nutrition practices among urban Lao women and their infants in Vientiane, Lao PDR (European Journal of Clinical Nutrition (2009) vol. 63 (323-331) 10.1038/sj.ejcn.1602928) European Journal of Clinical Nutrition, 63 (3), pp. 450-450. | Read more

Slesak G, Douangdala P, Inthalad S, Silisouk J, Vongsouvath M, Sengduangphachanh A, Moore CE, Mayxay M, Matsuoka H, Newton PN. 2009. Fatal Chromobacterium violaceum septicaemia in northern Laos, a modified oxidase test and post-mortem forensic family G6PD analysis Annals of Clinical Microbiology and Antimicrobials, 8 (1), pp. 24-24. Read abstract | Read more

Background: Chromobacterium violaceum is a Gram negative facultative anaerobic bacillus, found in soil and stagnant water, that usually has a violet pigmented appearance on agar culture. It is rarely described as a human pathogen, mostly from tropical and subtropical areas. Case presentation: A 53 year-old farmer died with Chromobacterium violaceum septicemia in Laos. A modified oxidase method was used to demonstrate that this violacious organism was oxidase positive. Forensic analysis of the glucose-6-phosphate dehydrogenase genotypes of his family suggest that the deceased patient did not have this possible predisposing condition. Conclusion: C. violaceum infection should be included in the differential diagnosis in patients presenting with community-acquired septicaemia in tropical and subtropical areas. The apparently neglected but simple modified oxidase test may be useful in the oxidase assessment of other violet-pigmented organisms or of those growing on violet coloured agar. © 2009 Slesak et al; licensee BioMed Central Ltd. Hide abstract

Paris DH, Blacksell SD, Newton PN, Day NP. 2008. Simple, rapid and sensitive detection of Orientia tsutsugamushi by loop-isothermal DNA amplification. Trans R Soc Trop Med Hyg, 102 (12), pp. 1239-1246. Read abstract | Read more

We present a loop-mediated isothermal PCR assay (LAMP) targeting the groEL gene, which encodes the 60kDa heat shock protein of Orientia tsutsugamushi. Evaluation included testing of 63 samples of contemporary in vitro isolates, buffy coats and whole blood samples from patients with fever. Detection limits for LAMP were assessed by serial dilutions and quantitation by real-time PCR assay based on the same target gene: three copies/microl for linearized plasmids, 26 copies/microl for VERO cell culture isolates, 14 copies/microl for full blood samples and 41 copies/microl for clinical buffy coats. Based on a limited sample number, the LAMP assay is comparable in sensitivity with conventional nested PCR (56kDa gene), with limits of detection well below the range of known admission bacterial loads of patients with scrub typhus. This inexpensive method requires no sophisticated equipment or sample preparation, and may prove useful as a diagnostic assay in financially poor settings; however, it requires further prospective validation in the field setting. Hide abstract

Newton PN. 2008. Different Clinical Expression of Murine Typhus and Scrub Typhus INTERNATIONAL JOURNAL OF INFECTIOUS DISEASES, 12 pp. E43-E43. | Read more

Dowell FE, Maghirang EB, Fernandez FM, Newton PN, Green MD. 2008. Detecting counterfeit antimalarial tablets by near-infrared spectroscopy. J Pharm Biomed Anal, 48 (3), pp. 1011-1014. Read abstract | Read more

Counterfeit antimalarial drugs are found in many developing countries, but it is challenging to differentiate between genuine and fakes due to their increasing sophistication. Near-infrared spectroscopy (NIRS) is a powerful tool in pharmaceutical forensics, and we tested this technique for discriminating between counterfeit and genuine artesunate antimalarial tablets. Using NIRS, we found that artesunate tablets could be identified as genuine or counterfeit with high accuracy. Multivariate classification models indicated that this discriminatory ability was based, at least partly, on the presence or absence of spectral signatures related to artesunate. This technique can be field-portable and requires little training after calibrations are developed, thus showing great promise for rapid and accurate fake detection. Hide abstract

Newton PN, Hampton CY, Alter-Hall K, Teerwarakulpana T, Prakongpan S, Ruangveerayuth R, White NJ, Day NP, Tudino MB, Mancuso N, Fernández FM. 2008. Characterization of "Yaa Chud" Medicine on the Thailand-Myanmar border: selecting for drug-resistant malaria and threatening public health. Am J Trop Med Hyg, 79 (5), pp. 662-669. Read abstract

Multidrug-resistant Plasmodium falciparum malaria is a severe public health problem on the Thailand-Myanmar border. Many villagers buy packets of 4-5 mixed medicines ("yaa chud") from shops without medical assessment as their first-line malaria treatment. In 2000-2001 a local researcher purchased 50 yaa chud from 44 shops around Mae Sot, Thailand and Myawaddy, Myanmar (Burma), for his wife who was said to be pregnant with fever and drowsiness. The tablets/capsules were provisionally identified by appearance and active ingredients determined in a subset by using mass and atomic spectrometry. The most frequently detected active ingredients were acetaminophen (22%), chlorpheniramine (13.4%), chloroquine (12.6%), tetracycline/doxycycline (11.4%), and quinine (5.1%). Only seven bags contained potentially curative medicine for malaria. A total of 82% of the bags contained medicines contraindicated in pregnancy. Inappropriate, ineffective antimalarial drugs on the Thailand-Myanmar border are likely to increase malaria morbidity, mortality and health costs and engender the emergence and spread of antimalarial drug resistance. Hide abstract

Nair S, Miller B, Barends M, Jaidee A, Patel J, Mayxay M, Newton P, Nosten F, Ferdig MT, Anderson TJ. 2008. Adaptive copy number evolution in malaria parasites. PLoS Genet, 4 (10), pp. e1000243. Read abstract | Read more

Copy number polymorphism (CNP) is ubiquitous in eukaryotic genomes, but the degree to which this reflects the action of positive selection is poorly understood. The first gene in the Plasmodium folate biosynthesis pathway, GTP-cyclohydrolase I (gch1), shows extensive CNP. We provide compelling evidence that gch1 CNP is an adaptive consequence of selection by antifolate drugs, which target enzymes downstream in this pathway. (1) We compared gch1 CNP in parasites from Thailand (strong historical antifolate selection) with those from neighboring Laos (weak antifolate selection). Two percent of chromosomes had amplified copy number in Laos, while 72% carried multiple (2-11) copies in Thailand, and differentiation exceeded that observed at 73 synonymous SNPs. (2) We found five amplicon types containing one to greater than six genes and spanning 1 to >11 kb, consistent with parallel evolution and strong selection for this gene amplification. gch1 was the only gene occurring in all amplicons suggesting that this locus is the target of selection. (3) We observed reduced microsatellite variation and increased linkage disequilibrium (LD) in a 900-kb region flanking gch1 in parasites from Thailand, consistent with rapid recent spread of chromosomes carrying multiple copies of gch1. (4) We found that parasites bearing dhfr-164L, which causes high-level resistance to antifolate drugs, carry significantly (p = 0.00003) higher copy numbers of gch1 than parasites bearing 164I, indicating functional association between genes located on different chromosomes but linked in the same biochemical pathway. These results demonstrate that CNP at gch1 is adaptive and the associations with dhfr-164L strongly suggest a compensatory function. More generally, these data demonstrate how selection affects multiple enzymes in a single biochemical pathway, and suggest that investigation of structural variation may provide a fast-track to locating genes underlying adaptation. Hide abstract

Parola P, Blacksell SD, Phetsouvanh R, Phongmany S, Rolain JM, Day NP, Newton PN, Raoult D. 2008. Genotyping of Orientia tsutsugamushi from humans with scrub typhus, Laos. Emerg Infect Dis, 14 (9), pp. 1483-1485. | Read more

Ricci C, Nyadong L, Yang F, Fernandez FM, Brown CD, Newton PN, Kazarian SG. 2008. Assessment of hand-held Raman instrumentation for in situ screening for potentially counterfeit artesunate antimalarial tablets by FT-Raman spectroscopy and direct ionization mass spectrometry. Anal Chim Acta, 623 (2), pp. 178-186. Read abstract | Read more

Pharmaceutical counterfeiting has become a significant public health problem worldwide and new, rapid, user-friendly, reliable and inexpensive methods for drug quality screening are needed. This work illustrates the chemical characterization of genuine and fake artesunate antimalarial tablets by portable Raman spectroscopy and validation by FT-Raman spectroscopy and ambient mass spectrometry. The applicability of a compact and robust portable Raman spectrometer (TruScan) for the in situ chemical identification of counterfeit tablets is reported. Hide abstract

Imwong M, Pukrittayakamee S, Pongtavornpinyo W, Nakeesathit S, Nair S, Newton P, Nosten F, Anderson TJ, Dondorp A, Day NP, White NJ. 2008. Gene amplification of the multidrug resistance 1 gene of Plasmodium vivax isolates from Thailand, Laos, and Myanmar. Antimicrob Agents Chemother, 52 (7), pp. 2657-2659. Read abstract | Read more

Plasmodium vivax mdr1 gene amplification, quantified by real-time PCR, was significantly more common on the western Thailand border (6 of 66 samples), where mefloquine pressure has been intense, than elsewhere in southeast Asia (3 of 149; P = 0.02). Five coding mutations in pvmdr1, independent of gene amplification, were also found. Hide abstract

Paris DH, Jenjaroen K, Blacksell SD, Phetsouvanh R, Wuthiekanun V, Newton PN, Day NP, Turner GD. 2008. Differential patterns of endothelial and leucocyte activation in 'typhus-like' illnesses in Laos and Thailand. Clin Exp Immunol, 153 (1), pp. 63-67. Read abstract | Read more

Scrub typhus is responsible for a large proportion of undifferentiated fevers in south-east Asia. The cellular tropism and pathophysiology of the causative agent, Orientia tsutsugamushi, remain poorly understood. We measured endothelial and leucocyte activation by soluble cell adhesion molecule enzyme-linked immunosorbent assays in 242 Lao and Thai patients with scrub or murine typhus, leptospirosis, dengue, typhoid and uncomplicated falciparum malaria on admission to hospital. Soluble E-selectin (sE-selectin) levels were lowest in dengue, sL-selectin highest in scrub typhus with a high sE-selectin to sL-selectin ratio in leptospirosis patients. In scrub typhus patients elevated sL-selectin levels correlated with the duration of skin rash (P = 0.03) and the presence of eschar (P = 0.03), elevated white blood cell (WBC) count (P = 0.007), elevated lymphocyte (P = 0.007) and neutrophil counts (P = 0.015) and elevated levels of sE-selectin correlated with the duration of illness before admission (P = 0.03), the presence of lymphadenopathy (P = 0.033) and eschar (P = 0.03), elevated WBC (P = 0.005) and neutrophil counts (P = 0.0003). In comparison, soluble selectin levels in murine typhus patients correlated only with elevated WBC counts (P = 0.03 for sE-selectin and sL-selectin). Soluble intercellular adhesion molecule-1 and soluble vascular adhesion molecule-1 levels were not associated significantly with any clinical parameters in scrub or murine typhus patients. The data presented suggest mononuclear cell activation in scrub typhus. As adhesion molecules direct leucocyte migration and induce inflammatory and immune responses, this may represent O. tsutsugamushi tropism during early dissemination, or local immune activation within the eschar. Hide abstract

Keoluangkhot V, Green MD, Nyadong L, Fernández FM, Mayxay M, Newton PN. 2008. Impaired clinical response in a patient with uncomplicated falciparum malaria who received poor-quality and underdosed intramuscular artemether. Am J Trop Med Hyg, 78 (4), pp. 552-555. Read abstract

We describe an adult with uncomplicated Plasmodium falciparum malaria who did not improve clinically despite 5 days of intramuscular artemether therapy. He was prescribed a lower dose (kg body weight) than that recommended, and a vial from the packet contained only 74% of the artemether dose as stated by the manufacturer. The combination of underdosing, poor-quality drug, and the intrinsic low bioavailability of artemether may have contributed to his poor clinical response. Analysis of the packaging and chemical "fingerprinting" of the artemether suggested that the drug was genuine but was either substandard or had deteriorated after manufacture. Hide abstract

Srour ML, Watt B, Phengdy B, Khansoulivong K, Harris J, Bennett C, Strobel M, Dupuis C, Newton PN. 2008. Noma in Laos: stigma of severe poverty in rural Asia. Am J Trop Med Hyg, 78 (4), pp. 539-542. Read abstract

Noma, or cancrum oris, is a debilitating necrotizing ulcerative stomatitis that destroys the mouth and face. It usually starts in early childhood and is associated with severe poverty, malnutrition, and infections. It is most frequently described from sub-Saharan Africa but is under-reported. There have been very few reports from Asia. We describe the clinical and social features of a series of 12 patients with noma from remote poor villages in rural Lao People's Democratic Republic (Laos). Noma is an ominous stigma of severe poverty and the description of this disease emphasizes the importance of poverty reduction and nutritional improvement in Lao development. In the meantime, more awareness of the problem and the importance of early therapy in acute noma by primary health care workers may reduce mortality and prevent progression to severe disfigurement. Hide abstract

Fernandez FM, Green MD, Newton PN. 2008. Prevalence and detection of counterfeit pharmaceuticals: A mini review INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 47 (3), pp. 585-590. | Read more

Paris DH, Blacksell SD, Stenos J, Graves SR, Unsworth NB, Phetsouvanh R, Newton PN, Day NP. 2008. Real-time multiplex PCR assay for detection and differentiation of rickettsiae and orientiae. Trans R Soc Trop Med Hyg, 102 (2), pp. 186-193. Read abstract | Read more

The high incidence of rickettsial diseases in Southeast Asia necessitates rapid and accurate diagnostic tools for a broad range of rickettsial agents, including Orientia tsutsugamushi (scrub typhus) and Rickettsia typhi (murine typhus), but also spotted fever group infections, which are increasingly reported. We present an SYBR-Green-based, real-time multiplex PCR assay for rapid identification and differentiation of scrub typhus group, typhus group and spotted fever group rickettsiae using 47kDa, gltA and ompB gene targets. Detection limits for amplification of these genes in reference strains ranged from 24 copies/microl, 5 copies/microl and 1 copy/microl in multiplex and 2 copies/microl, 1 copy/microl and 1 copy/microl in single template format, respectively. Differentiation by melt-curve analysis led to distinct melt temperatures for each group-specific amplicon. The assay was subjected to 54 samples, of which all cell-culture and 75% of characterised clinical buffy coat samples were correctly identified. Real-time PCR has the advantage of reliably detecting and differentiating rickettsial and orientia cell-culture isolates in a single-template assay, compared with the more time-consuming and laborious immunofluorescence assay. However, further optimisation and validation on samples taken directly from patients to assess its clinical diagnostic utility is required. Hide abstract

Newton PN, Fernández FM, Plançon A, Mildenhall DC, Green MD, Ziyong L, Christophel EM, Phanouvong S et al. 2008. A collaborative epidemiological investigation into the criminal fake artesunate trade in South East Asia. PLoS Med, 5 (2), pp. e32. Read abstract | Read more

Since 1998 the serious public health problem in South East Asia of counterfeit artesunate, containing no or subtherapeutic amounts of the active antimalarial ingredient, has led to deaths from untreated malaria, reduced confidence in this vital drug, large economic losses for the legitimate manufacturers, and concerns that artemisinin resistance might be engendered. Hide abstract

Paris DH, Blacksell SD, Newton PN, Day NPJ. 2008. Simple, rapid and sensitive detection of Orientia tsutsugamushi by loop-isothermal DNA amplification Transactions of the Royal Society of Tropical Medicine and Hygiene,

Lee SJ, Stepniewska K, Anstey N, Ashley E, Barnes K, Binh TQ, D'Alessandro U, Day NP et al. 2008. The relationship between the haemoglobin concentration and the haematocrit in Plasmodium falciparum malaria. Malar J, 7 (1), pp. 149. Read abstract | Read more

Malaria is a very important cause of anaemia in tropical countries. Anaemia is assessed either by measurement of the haematocrit or the haemoglobin concentration. For comparisons across studies, it is often necessary to derive one measure from the other. Hide abstract

Peacock SJ, Newton PN. 2008. Public health impact of establishing the cause of bacterial infections in rural Asia. Trans R Soc Trop Med Hyg, 102 (1), pp. 5-6. Read abstract | Read more

Recent studies delineating bacterial causes of fever in rural Asia indicate a major role for several previously under-recognized pathogens, including Rickettsia and Leptospira. The use of blood culture for the first time to investigate patients with febrile illness in rural Asia has also revealed some unexpected findings, e.g. Staphylococcus aureus is the major cause of bacteraemia in children aged <1 year in Laos. The spread of antimicrobial-resistant pathogens such as MRSA into rural Asia has already occurred and requires monitoring. These factors have major implications for empirical therapy of fever. Initiatives are urgently needed to strengthen the infrastructure of microbiology in rural Asia. Hide abstract

Barennes H, Sayasone S, Odermatt P, De Bruyne A, Hongsakhone S, Newton PN, Vongphrachanh P, Martinez-Aussel B, Strobel M, Dupouy-Camet J. 2008. A major trichinellosis outbreak suggesting a high endemicity of Trichinella infection in northern Laos. Am J Trop Med Hyg, 78 (1), pp. 40-44. Read abstract

Trichinellosis is an important and under-recognized food-borne zoonosis in Southeast Asia. After 30 years of no reports, a small outbreak was described in Central Lao PDR (Laos) in 2003. Here we report a large outbreak of at least 650 estimated patients in Udomxay (northern Laos) in June 2005. Trichinella ELISA assays on serum from 133 patients and Western blot assays on 16 patients were positive in 67.6% and 81.2%, respectively. No deaths were recorded. Consumption of uncooked or fermented pork at funeral and wedding ceremonies was the main source of infection. Larvae of Trichinella spiralis were found in 1 of 11 local pigs not involved in this outbreak. The results suggest that trichinellosis may be an under-recognized but important endemic disease in Laos and reinforces the need to urgently implement veterinary and educational programs. Hide abstract

Phetsouvanh R, Nakatsu M, Arakawa E, Davong V, Vongsouvath M, Lattana O, Moore CE, Nakamura S, Newton PN. 2008. Fatal bacteremia due to immotile Vibrio cholerae serogroup O21 in Vientiane, Laos - a case report. Ann Clin Microbiol Antimicrob, 7 (1), pp. 10. Read abstract | Read more

Human infections with non-O1, non-O139 V. cholerae have been described from Laos. Elsewhere, non cholera-toxin producing, non-O1, non-O139 V. cholerae have been described from blood cultures and ascitic fluid, although they are exceedingly rare isolates. Hide abstract

Blacksell SD, Mammen MP, Thongpaseuth S, Gibbons RV, Jarman RG, Jenjaroen K, Nisalak A, Phetsouvanh R, Newton PN, Day NP. 2008. Evaluation of the Panbio dengue virus nonstructural 1 antigen detection and immunoglobulin M antibody enzyme-linked immunosorbent assays for the diagnosis of acute dengue infections in Laos. Diagn Microbiol Infect Dis, 60 (1), pp. 43-49. Read abstract | Read more

We evaluated 2 commercial enzyme-linked immunosorbent assays (ELISAs) for the diagnosis of dengue infection; one a serologic test for immunoglobulin M (IgM) antibodies, the other based on detection of dengue virus nonstructural 1 (NS1) antigen. Using gold standard reference serology on paired sera, 41% (38/92 patients) were dengue confirmed, with 4 (11%) acute primary and 33 (87%) acute secondary infections (1 was of indeterminate status). Sensitivity of the NS1-ELISA was 63% (95% confidence interval [CI], 53-73) on admission samples but was much less sensitive (5%; 95% CI, 1-10) on convalescent samples. The IgM capture ELISA had a lower but statistically equivalent sensitivity compared with the NS1-ELISA for admission samples (45%; 95% CI, 35-55) but was more sensitive on convalescent samples (58%; 95% CI, 48-68). The results of the NS1 and IgM capture ELISAs were combined using a logical OR operator, increasing the sensitivity for admission samples (79%; 95% CI, 71-87), convalescent samples (63%; 95% CI, 53-73), and all samples (71%; 95% CI, 65-78). Hide abstract

Chau TT, Campbell JI, Galindo CM, Van Minh Hoang N, Diep TS, Nga TT, Van Vinh Chau N, Tuan PQ et al. 2007. Antimicrobial drug resistance of Salmonella enterica serovar typhi in asia and molecular mechanism of reduced susceptibility to the fluoroquinolones. Antimicrob Agents Chemother, 51 (12), pp. 4315-4323. Read abstract | Read more

This study describes the pattern and extent of drug resistance in 1,774 strains of Salmonella enterica serovar Typhi isolated across Asia between 1993 and 2005 and characterizes the molecular mechanisms underlying the reduced susceptibilities to fluoroquinolones of these strains. For 1,393 serovar Typhi strains collected in southern Vietnam, the proportion of multidrug resistance has remained high since 1993 (50% in 2004) and there was a dramatic increase in nalidixic acid resistance between 1993 (4%) and 2005 (97%). In a cross-sectional sample of 381 serovar Typhi strains from 8 Asian countries, Bangladesh, China, India, Indonesia, Laos, Nepal, Pakistan, and central Vietnam, collected in 2002 to 2004, various rates of multidrug resistance (16 to 37%) and nalidixic acid resistance (5 to 51%) were found. The eight Asian countries involved in this study are home to approximately 80% of the world's typhoid fever cases. These results document the scale of drug resistance across Asia. The Ser83-->Phe substitution in GyrA was the predominant alteration in serovar Typhi strains from Vietnam (117/127 isolates; 92.1%). No mutations in gyrB, parC, or parE were detected in 55 of these strains. In vitro time-kill experiments showed a reduction in the efficacy of ofloxacin against strains harboring a single-amino-acid substitution at codon 83 or 87 of GyrA; this effect was more marked against a strain with a double substitution. The 8-methoxy fluoroquinolone gatifloxacin showed rapid killing of serovar Typhi harboring both the single- and double-amino-acid substitutions. Hide abstract

Amornchai P, Chierakul W, Wuthiekanun V, Mahakhunkijcharoen Y, Phetsouvanh R, Currie BJ, Newton PN, van Vinh Chau N, Wongratanacheewin S, Day NP, Peacock SJ. 2007. Accuracy of Burkholderia pseudomallei identification using the API 20NE system and a latex agglutination test. J Clin Microbiol, 45 (11), pp. 3774-3776. Read abstract | Read more

In an evaluation of the API 20NE for the identification of Burkholderia spp., 792/800 (99%) Burkholderia pseudomallei and 17/19 (89%) B. cepacia isolates were correctly identified but 10 B. mallei and 98 B. thailandensis isolates were not correctly identified. A latex agglutination test was positive for 796/800 (99.5%) B. pseudomallei isolates and negative for 120 other oxidase-positive gram-negative bacilli. Hide abstract

Blacksell SD, Bell D, Kelley J, Mammen MP, Gibbons RV, Jarman RG, Vaughn DW, Jenjaroen K et al. 2007. Prospective study to determine accuracy of rapid serological assays for diagnosis of acute dengue virus infection in Laos. Clin Vaccine Immunol, 14 (11), pp. 1458-1464. Read abstract | Read more

There is an urgent need for accurate and simple dengue virus infection diagnostic assays in limited-resource settings of dengue endemicity, to assist patient management. Using a panel of reference samples (S. D. Blacksell, P. N. Newton, D. Bell, J. Kelley, M. P. Mammen, D. W. Vaughn, V. Wuthiekanun, A. Sungkakum, A. Nisalak, and N. P. Day, Clin. Infect. Dis. 42:1127-1134, 2006), we recently evaluated eihgt commercially available immunochromatographic rapid diagnostic tests (RDTs) designed to detect dengue virus-specific immunoglobulin M (IgM) and/or IgG. We found that 6/8 RDTs had sensitivities of less than 50% (range, 6 to 65%), but specificities were generally high. Here, in conjuction with dengue virus serotyping by reverse transcriptase PCR and in the limited-resource setting of Laos, where dengue virus is endemic, we evaluated the same eight RDTs against a previously validated dengue IgM/IgG enzyme-linked immunosorbent assay for diagnosis of acute dengue virus infection. Paired serum samples were collected from 87 patients, of whom 38 had confirmed dengue virus infections (4 had primary infections, 33 had secondary infections, and 1 had an infection of indeterminate status). RDT sensitivity was low, with 7/8 RDTs having admission sample sensitivities of less than 20% (range, 4 to 26%). The majority (6/8) of the RDTs, demonstrated high specificity (>95%). Kappa statistic values ranged from 6 to 54% for the RDTs, demonstrating poor to moderate variation between three operators. No RDT adequately differentiated between primary and secondary dengue virus infections. The findings of this study suggest that currently available RDTs based on the detection of IgM antibodies for the diagnosis of acute dengue virus infections are unlikely to be useful for patient management. Hide abstract

Keomany S, Mayxay M, Souvannasing P, Vilayhong C, Stuart BL, Srour L, Newton PN. 2007. Toad poisoning in Laos. Am J Trop Med Hyg, 77 (5), pp. 850-853. Read abstract

We describe two patients who developed severe illness after eating the skin and eggs of a toad, probably Bufo melanostictus Schneider, in southeastern Laos. One boy died, and one developed a digoxin toxicity-like syndrome with bradycardia and heart failure but survived. A telephone survey of 16 Lao provincial hospitals suggested that toad poisoning occurs in at least six provinces. That 93% of villagers in three villages in southeastern Laos were aware that toads are poisonous but that 51% had encountered patients with toad toxicity suggests that the potential gravity is not appreciated. These data indicate that toad poisoning may be underestimated and that education on the seriousness of toad toxins could be a useful public health measure. Hide abstract

Ricci C, Eliasson C, Macleod NA, Newton PN, Matousek P, Kazarian SG. 2007. Characterization of genuine and fake artesunate anti-malarial tablets using Fourier transform infrared imaging and spatially offset Raman spectroscopy through blister packs. Anal Bioanal Chem, 389 (5), pp. 1525-1532. Read abstract | Read more

In support of the efforts to combat the illegal sale and distribution of counterfeit anti-malarial drugs, we evaluated a new analytical approach for the characterization and fast screening of fake and genuine artesunate tablets using a combination of Raman spectroscopy, Spatially Offset Raman Spectroscopy (SORS) and Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) imaging. Vibrational spectroscopy provided chemically specific information on the composition of the tablets; the complementary nature of Raman scattering and FTIR imaging allowed the characterization of both the overall and surface composition of the tablets. The depth-resolving power of the SORS approach provided chemically specific information on the overall composition of the tablets, non-invasively, through a variety of packaging types. Spatial imaging of the tablet surface (using ATR-FTIR) identified the location of domains of excipients and active ingredients with high sensitivity and enhanced spatial resolution. The advantages provided by a combination of SORS and ATR-FTIR imaging in this context confirm its potential for inclusion in the analytical protocol for forensic investigation of counterfeit medicines. Hide abstract

Newton PN, Mayxay M, Taylor A, White NJ. 2007. Untitled TROPICAL MEDICINE & INTERNATIONAL HEALTH, 12 (10), pp. 1272-1273.

Mayxay M, Nair S, Sudimack D, Imwong M, Tanomsing N, Pongvongsa T, Phompida S, Phetsouvanh R, White NJ, Anderson TJ, Newton PN. 2007. Combined molecular and clinical assessment of Plasmodium falciparum antimalarial drug resistance in the Lao People's Democratic Republic (Laos). Am J Trop Med Hyg, 77 (1), pp. 36-43. Read abstract

Molecular markers provide a rapid and relatively inexpensive approach for assessing antimalarial drug susceptibility. We collected 884 Plasmodium falciparum-infected blood samples from 17 Lao provinces. Each sample was genotyped for 11 codons in the chloroquine resistance transporter (pfcrt), dihydrofolate reductase (pfdhfr), and dihydropteroate synthase (pfdhps) genes. The samples included 227 collected from patients recruited to clinical trials. The pfcrt K76T mutation was an excellent predictor of treatment failure for both chloroquine and chloroquine plus sulfadoxine-pyrimethamine, and mutations in both pfdhfr and pfdhps were predictive of sulfadoxine-pyrimethamine treatment failure. In multivariate analysis, the presence of the pfdhfr triple mutation (51 + 59 + 108) was strongly and independently correlated with sulfadoxine-pyrimethamine failure (odds ratio = 9.1, 95% confidence interval = 1.4-60.2, P = 0.017). Considerable geographic heterogeneity in allele frequencies occurred at all three loci with lower frequencies of mutant alleles in southern than in northern Laos. These findings suggest that chloroquine and sulfadoxine-pyrimethamine are no longer viable therapy in this country. Hide abstract

Imwong M, Nair S, Pukrittayakamee S, Sudimack D, Williams JT, Mayxay M, Newton PN, Kim JR et al. 2007. Contrasting genetic structure in Plasmodium vivax populations from Asia and South America. Int J Parasitol, 37 (8-9), pp. 1013-1022. Read abstract | Read more

Populations of Plasmodium falciparum show striking differences in linkage disequilibrium, population differentiation and diversity, but only fragmentary data exists on the genetic structure of Plasmodium vivax. We genotyped nine tandem repeat loci bearing 2-8 bp motifs from 345 P. vivax infections collected from three Asian countries and from five locations in Colombia. We observed 9-37 alleles per locus and high diversity (He=0.72-0.79, mean=0.75) in all countries. Numbers of multiple clone infections varied considerably: these were rare in Colombia and India, but > 60% of isolates carried multiple alleles in at least one locus in Thailand and Laos. However, only one or two of the nine loci show >1 allele in many samples, suggesting that mutation within infections may result in overestimation of true multiple carriage rates. Identical nine-locus genotypes were frequently found in Colombian populations, contributing to strong linkage disequilibrium. These identical genotypes were strongly clustered in time, consistent with epidemic transmission of clones and subsequent breakdown of allelic associations, suggesting high rates of inbreeding and low effective recombination rates in this country. In contrast, identical genotypes were rare and loci were randomly associated in all three Asian populations, consistent with higher rates of outcrossing and recombination. We observed low but significant differentiation between different Asian countries (standardized FST = 0.13-0.45). In comparison, we see greater differentiation between collection locations within Colombia (standardized FST = 0.4-0.7), and strong differentiation between continents (standardized FST = 0.48-0.79). The observed heterogeneity in multiple clone carriage rates, linkage disequilibrium and population differentiation are similar in some, but not all, respects to those observed in P. falciparum, and have important implications for the design of association mapping studies, and interpretation of P. vivax epidemiology. Hide abstract

Paris DH, Jenjaroen K, Blacksell SD, Rattanaphone P, Newton PN, Turner GD, Day NP. 2007. Differential patterns of endothelial activation in 'typhus-like' illness TROPICAL MEDICINE & INTERNATIONAL HEALTH, 12 pp. 189-189.

Mayxay M, Pongvongsa T, Phompida S, Phetsouvanh R, White NJ, Newton PN. 2007. Diagnosis and management of malaria by rural community health providers in the Lao People's Democratic Republic (Laos). Trop Med Int Health, 12 (4), pp. 540-546. Read abstract | Read more

We assessed the knowledge of malaria diagnosis and management by community health providers in rural Vientiane and Savannakhet Provinces, Lao PDR. Sixty health providers (17 pharmacy owners/drug sellers and 43 village health volunteers) were interviewed. All diagnosed malaria using symptoms and signs only; 14% were aware of >2 criteria for the diagnosis of severe malaria. Although chloroquine and quinine, the then recommended Lao national policy for uncomplicated malaria treatment, were the most common antimalarials prescribed - 65% gave incorrect doses and 70% did not know the side effects. Although not recommended by the then national policy, 27% of the health providers used combinations of antimalarials as they considered monotherapy ineffective. This study strongly suggests that further training of Lao rural health providers in malaria diagnosis and management is needed to improve the quality of health services in areas remote from district hospitals. Hide abstract

Newton PN, Green MD, Fernandez F. 2007. Counterfeit artemisinin derivatives and Africa: update from authors. PLoS Med, 4 (3), pp. e139. | Read more

Blacksell SD, Myint KS, Khounsy S, Phruaravanh M, Mammen MP, Day NP, Newton PN. 2007. Prevalence of hepatitis E virus antibodies in pigs: implications for human infections in village-based subsistence pig farming in the Lao PDR. Trans R Soc Trop Med Hyg, 101 (3), pp. 305-307. Read abstract | Read more

We report a high seroprevalence of hepatitis E virus (HEV) in pigs in the Lao PDR. HEV seroprevalence was 51.2% (300/586) amongst abattoir pigs and 15.3% (46/301) amongst village pigs. The age distribution suggested previous in-village HEV pig infections. These findings suggest a zoonotic risk associated with village-based smallholder pig farming. Hide abstract

Mayxay M, Taylor AM, Khanthavong M, Keola S, Pongvongsa T, Phompida S, Phetsouvanh R, White NJ, Newton PN. 2007. Thiamin deficiency and uncomplicated falciparum malaria in Laos. Trop Med Int Health, 12 (3), pp. 363-369. Read abstract | Read more

Thiamin deficiency complicates severe Plasmodium falciparum malaria in Thailand and may contribute to acidosis. We therefore estimated the frequency of biochemical thiamin deficiency in patients presenting with uncomplicated falciparum malaria in southern Laos. Hide abstract

Nyadong L, Green MD, De Jesus VR, Newton PN, Fernández FM. 2007. Reactive desorption electrospray ionization linear ion trap mass spectrometry of latest-generation counterfeit antimalarials via noncovalent complex formation. Anal Chem, 79 (5), pp. 2150-2157. Read abstract | Read more

Desorption electrospray ionization mass spectrometry (DESI MS) is rapidly becoming accepted as a powerful surface characterization tool for a wide variety of samples in the open air. Besides its well-established high-throughput capabilities, a unique feature of DESI is that chemical reactions between the charged spray microdroplets and surface molecules can be exploited to enhance ionization. Here, we present a rapid screening assay for artesunate antimalarials based on reactive DESI. Artesunate is a vital therapy for Plasmodium falciparum malaria, but artesunate tablets have been counterfeited on a very large scale in SE Asia, and more recently in Africa. For this reason, faster and more sensitive screening tests are urgently needed. The proposed DESI assay is based on the formation of stable noncovalent complexes between linear alkylamines dissolved in the DESI spray solution and artesunate molecules exposed on the tablet surface. We found that, depending on amine type and concentration, a sensitivity gain of up to 170x can be obtained, in comparison to reagent-less DESI. Hexylamine (Hex), dodecylamine (DDA), and octadecylamine (ODA) produced proton-bound noncovalent complexes with gas-phase stabilities, increasing in the order [M + Hex + H]+ < [M + DDA + H]+ < [M + ODA + H]+. Tandem MS experiments revealed that complex formation occurred by hydrogen bonding between the amine nitrogen and the ether-like moieties within the artesunate lactone ring. After the reactive DESI assay was fully characterized, it was applied to a set of recently collected suspicious artesunate tablets purchased in shops and pharmacies in SE Asia. Not only did we find that these samples were counterfeits, but we also detected the presence of several wrong active ingredients. Of particular concern was the positive detection of artesunate traces in the surface of one of the samples, which we quantified with standard chromatographic techniques. Hide abstract

de Veij M, Vandenabeele P, Hall KA, Fernandez FM, Green MD, White NJ, Dondorp AM, Newton PN, Moens L. 2007. Fast detection and identification of counterfeit antimalarial tablets by Raman spectroscopy JOURNAL OF RAMAN SPECTROSCOPY, 38 (2), pp. 181-187. Read abstract | Read more

During the last decade there has been an apparent increase in the prevalence of counterfeit medicines in developing as well as developed countries. The pivotal antimalarial artesunate has been counterfeited on a large scale in SE Asia. In this work, the possibilities of Raman spectroscopy are explored as a fast and reliable screening method for the detection of counterfeit artesunate tablets. In this study, 50 'artesunate tablets', purchased in SE Asia, were examined. This spectroscopic method was able to distinguish between genuine and counterfeit artesunate and to identify the composition of the counterfeit tablets. These contained no detectable levels of artesunate, but consisted mostly of starch, calcite (CaCO3), and paracetamol (4-acetamidophenol). In one particular case an admixture of rutile (TiO2) and artesunate was detected. The results of the investigation by Raman spectroscopy were in agreement with those of colorimetric tests and of liquid chromatography-mass spectrometry on the artesunate. Moreover, principal components analysis (PCA) was combined with hierarchical cluster analysis to establish an automated approach for the discrimination between different groups of counterfeits and genuine artesunate tablets. These results demonstrate that Raman spectroscopy combined with multivariate analysis is a promising and reliable methodology for the fast characterization of genuine and counterfeit artesunate antimalarial tablets. Copyright © 2006 John Wiley & Sons, Ltd. Hide abstract

McGready R, Kaveri SV, Lacroix-Desmazes S, Krudsood S, Newton PN. 2007. Acquired haemophilia A in early pregnancy associated with Plasmodium vivax malaria and hyperthyroidism. Aust N Z J Obstet Gynaecol, 47 (1), pp. 76-77. | Read more

Mayxay M, Barends M, Brockman A, Jaidee A, Nair S, Sudimack D, Pongvongsa T, Phompida S et al. 2007. In vitro antimalarial drug susceptibility and pfcrt mutation among fresh Plasmodium falciparum isolates from the Lao PDR (Laos). Am J Trop Med Hyg, 76 (2), pp. 245-250. Read abstract

Recent drug trials in Laos have shown high levels of Plasmodium falciparum resistance to chloroquine, but there are no published data on in vitro antimalarial drug susceptibility. We used the double-site enzyme-linked pLDH immunodetection (DELI) assay to estimate the in vitro antimalarial drug susceptibility of 108 fresh P. falciparum isolates from southern Laos. The geometric mean (95% confidence interval) 50% inhibitory concentration values (nmol/L) were 152.4 (123.8-187.6) for chloroquine, 679.8 (533.8-863.0) for quinine, 45.9 (37.9-55.7) for mefloquine, 5.0 (4.4-6.4) for artesunate, 6.3 (4.5-8.9) for dihydroartemisinin, and 59.1 (46.4-75.3) for lumefantrine. The proportion of isolates defined as resistant were 65%, 40%, and 8% for chloroquine, quinine, and mefloquine, respectively. Of 53 isolates genotyped for the pfcrt T76K chloroquine-resistance mutation, 48 (91%) were mutants. P. falciparum in Laos is multi-drug resistant; antimalarial immunity resulting from the use of ineffective chloroquine before 2005 probably contributes significantly to the therapeutic responses in clinical trials. Hide abstract

Green MD, Nettey H, Villalva Rojas O, Pamanivong C, Khounsaknalath L, Grande Ortiz M, Newton PN, Fernández FM, Vongsack L, Manolin O. 2007. Use of refractometry and colorimetry as field methods to rapidly assess antimalarial drug quality. J Pharm Biomed Anal, 43 (1), pp. 105-110. Read abstract | Read more

The proliferation of counterfeit and poor-quality drugs is a major public health problem; especially in developing countries lacking adequate resources to effectively monitor their prevalence. Simple and affordable field methods provide a practical means of rapidly monitoring drug quality in circumstances where more advanced techniques are not available. Therefore, we have evaluated refractometry, colorimetry and a technique combining both processes as simple and accurate field assays to rapidly test the quality of the commonly available antimalarial drugs; artesunate, chloroquine, quinine, and sulfadoxine. Method bias, sensitivity, specificity and accuracy relative to high-performance liquid chromatographic (HPLC) analysis of drugs collected in the Lao PDR were assessed for each technique. The HPLC method for each drug was evaluated in terms of assay variability and accuracy. The accuracy of the combined method ranged from 0.96 to 1.00 for artesunate tablets, chloroquine injectables, quinine capsules, and sulfadoxine tablets while the accuracy was 0.78 for enterically coated chloroquine tablets. These techniques provide a generally accurate, yet simple and affordable means to assess drug quality in resource-poor settings. Hide abstract

Ricci C, Nyadong L, Fernandez FM, Newton PN, Kazarian SG. 2007. Combined Fourier-transform infrared imaging and desorption electrospray-ionization linear ion-trap mass spectrometry for analysis of counterfeit antimalarial tablets. Anal Bioanal Chem, 387 (2), pp. 551-559. Read abstract | Read more

This paper reports use of a combination of Fourier-transform infrared (FTIR) spectroscopic imaging and desorption electrospray ionization linear ion-trap mass spectrometry (DESI MS) for characterization of counterfeit pharmaceutical tablets. The counterfeit artesunate antimalarial tablets were analyzed by both techniques. The results obtained revealed the ability of FTIR imaging in non-destructive micro-attenuated total reflection (ATR) mode to detect the distribution of all components in the tablet, the identities of which were confirmed by DESI MS. Chemical images of the tablets were obtained with high spatial resolution. The FTIR spectroscopic imaging method affords inherent chemical specificity with rapid acquisition of data. DESI MS enables high-sensitivity detection of trace organic compounds. Combination of these two orthogonal surface-characterization methods has great potential for detection and analysis of counterfeit tablets in the open air and without sample preparation. Hide abstract

Green MD, Nettey H, Rojas OV, Pamanivong C, Khounsaknalath L, Ortiz MG, Newton PN, Fernández FM, Vongsack L, Manolin O. 2007. Corrigendum to "Use of refractometry and colorimetry as field methods to rapidly assess antimalarial drug quality" [J. Pharm. Biomed. Anal. 43 (2007) 105-110] (DOI:10.1016/j.jpba.2006.06.047) Journal of Pharmaceutical and Biomedical Analysis, 43 (5), pp. 1890-1890. | Read more

Slesak G, Phanthavong P, Rasphone O, Luangxay K, Anoulakkham P, Pahatsalang V, Soumphonphakdy B, White JA, Newton PN. 2007. Obstructive biliary ascariasis with cholangitis and hepatic abscesses in Laos: a case report with gall bladder ultrasound video. J Infect, 54 (4), pp. e233-e235. Read abstract | Read more

A 12-year-old Lao boy with obstructive biliary Ascaris infection is described and video of the gallbladder ultrasound presented. The patient developed severe complications of obstructive cholangitis, a large right pleural effusion and hepatic abscesses requiring prolonged antibiotic therapy. The differential diagnosis of worms in the gall-bladder is discussed. Hide abstract

Mayxay M, Khomthilat T, Souvannasing P, Phounesavath K, Vorasane B, Keomany S, Douangdala P, Philavong K, Srour L, Newton PN. 2007. Factors associated with a measles outbreak in children admitted at Mahosot Hospital, Vientiane, Laos. BMC Public Health, 7 (1), pp. 193. Read abstract | Read more

In 2002 and 2003 there were large outbreaks of measles in many provinces of Laos, including in Vientiane. We therefore conducted a study to determine risk factors associated with measles amongst children admitted at Mahosot Hospital, Vientiane. Hide abstract

Newton PN, Barnes KI, Smith PJ, Evans AC, Chierakul W, Ruangveerayuth R, White NJ. 2006. The pharmacokinetics of intravenous artesunate in adults with severe falciparum malaria. Eur J Clin Pharmacol, 62 (12), pp. 1003-1009. Read abstract | Read more

Intravenous artesunate is commonly used in the emergency treatment of patients with severe falciparum malaria in Asia. The choice of doses used has been empirical. To inform dosage recommendations we assessed the pharmacokinetics of intravenous artesunate after the first dose. Hide abstract

Sayasone S, Odermatt P, Vongphrachanh P, Keoluangkot V, Dupouy-Camet J, Newton PN, Strobel M. 2006. A trichinellosis outbreak in Borikhamxay Province, Lao PDR. Trans R Soc Trop Med Hyg, 100 (12), pp. 1126-1129. Read abstract | Read more

Trichinellosis is documented in Southeast Asia, particularly in Thailand and China. Data from Lao PDR are lacking. An outbreak investigation was conducted in Borikhamxay Province after three patients with suspected trichinellosis consulted the Mahosot Hospital, Vientiane. In total, 22 trichinellosis cases were identified; 21 cases could be confirmed by Western blot. High fever (100%), muscle pain (91%), upper eyelid oedema (86%) and diarrhoea (59%) were observed. Among the 22 patients, 86% had consumed pork meat from the same source. This is the first report of an outbreak investigation in Lao PDR since 1975. It shows that the incidence of trichinellosis is much higher than currently thought. Hide abstract

Phetsouvanh R, Phongmany S, Soukaloun D, Rasachak B, Soukhaseum V, Soukhaseum S, Frichithavong K, Khounnorath S et al. 2006. Causes of community-acquired bacteremia and patterns of antimicrobial resistance in Vientiane, Laos. Am J Trop Med Hyg, 75 (5), pp. 978-985. Read abstract

There is no published information on the causes of bacteremia in the Lao PDR (Laos). Between 2000 and 2004, 4512 blood culture pairs were taken from patients admitted to Mahosot Hospital, Vientiane, Laos, with suspected community-acquired bacteremia; 483 (10.7%) cultures grew a clinically significant community-acquired organism, most commonly Salmonella enterica serovar typhi (50.9%), Staphylococcus aureus (19.0%), and Escherichia coli (12.4%). S. aureus bacteremia was common among infants (69.2%), while children 1-5 years had a high frequency of typhoid (44%). Multi-drug-resistant S. Typhi was rare (6%). On multiple logistic regression analysis, typhoid was associated with younger age, longer illness, diarrhea, higher admission temperature, and lower peripheral white blood cell count than non-typhoidal bacteremia. Empirical parenteral ampicillin and gentamicin would have some activity against approximately 88% of clinically significant isolates at a cost of US $1.4/day, an important exception being B. pseudomallei. Bacteremic infants in this setting require an anti-staphylococcal antibiotic. Hide abstract

Hall KA, Newton PN, Green MD, De Veij M, Vandenabeele P, Pizzanelli D, Mayxay M, Dondorp A, Fernandez FM. 2006. Characterization of counterfeit artesunate antimalarial tablets from southeast Asia. Am J Trop Med Hyg, 75 (5), pp. 804-811. Read abstract

In southeast Asia, the widespread high prevalence of counterfeits tablets of the vital antimalarial artesunate is of great public health concern. To assess the seriousness of this problem, we quantified the amount of active ingredient present in artesunate tablets by liquid chromatography coupled to mass spectrometry. This method, in conjunction with analysis of the packaging, classified tablets as genuine, substandard, or fake and validated results of the colorimetric Fast Red TR test. Eight (35%) of 23 fake artesunate samples contained the wrong active ingredients, which were identified as different erythromycins and paracetamol. Raman spectroscopy identified calcium carbonate as an excipient in 9 (39%) of 23 fake samples. Multivariate unsupervised pattern recognition results indicated two major clusters of artesunate counterfeits, those with counterfeit foil stickers and containing calcium carbonate, erythromycin, and paracetamol, and those with counterfeit holograms and containing starch but without evidence of erythromycin or paracetamol. Hide abstract

Blacksell SD, Khounsy S, Phetsouvanh R, Newton PN. 2006. A simple and inexpensive container for the transport of biological specimens in limited resource situations. Trans R Soc Trop Med Hyg, 100 (11), pp. 1084-1086. Read abstract | Read more

We describe a diagnostic specimen transport container that is appropriate for limited resource or emergency settings. The transport container is constructed from polyvinyl chloride (PVC) plumbing pipe, which is readily available and inexpensive (US$1-2, depending on size) and has wide flexibility of size due to the range of PVC pipe dimensions available. The PVC transporters are durable, water-resistant and may be easily decontaminated. They have been adapted for the transport of blood culture bottles from provincial hospitals in Laos, where, during a 2-year period, 380 PVC tubes containing blood culture bottles were transported without any leakage or breakage. We have found the PVC transporter to be a useful and cost-efficient durable alternative that meets IATA Packing Instruction 650 biological transport container requirements. Hide abstract

Blacksell SD, Smythe L, Phetsouvanh R, Dohnt M, Hartskeerl R, Symonds M, Slack A, Vongsouvath M et al. 2006. Limited diagnostic capacities of two commercial assays for the detection of Leptospira immunoglobulin M antibodies in Laos. Clin Vaccine Immunol, 13 (10), pp. 1166-1169. Read abstract | Read more

The diagnostic utility of immunochromatographic (Leptotek) and enzyme-linked immunosorbent assay (ELISA; Panbio) tests for the detection of Leptospira immunoglobulin M antibodies was assessed in febrile adults admitted in Vientiane, Laos. Both tests demonstrated poor diagnostic accuracy using admission serum (Leptotek sensitivity of 47.3% and specificity of 75.5%: ELISA sensitivity of 60.9% and specificity of 65.6%) compared to the Leptospira "gold standard" microscopic agglutination test. Hide abstract

Newton PN, Green MD, Fernández FM, Day NP, White NJ. 2006. Counterfeit anti-infective drugs. Lancet Infect Dis, 6 (9), pp. 602-613. Read abstract | Read more

The production of counterfeit or substandard anti-infective drugs is a widespread and under-recognised problem that contributes to morbidity, mortality, and drug resistance, and leads to spurious reporting of resistance and toxicity and loss of confidence in health-care systems. Counterfeit drugs particularly affect the most disadvantaged people in poor countries. Although advances in forensic chemical analysis and simple field tests will enhance drug quality monitoring, improved access to inexpensive genuine medicines, support of drug regulatory authorities, more open reporting, vigorous law enforcement, and more international cooperation with determined political leadership will be essential to counter this threat. Hide abstract

Blacksell SD, Doust JA, Newton PN, Peacock SJ, Day NP, Dondorp AM. 2006. A systematic review and meta-analysis of the diagnostic accuracy of rapid immunochromatographic assays for the detection of dengue virus IgM antibodies during acute infection. Trans R Soc Trop Med Hyg, 100 (8), pp. 775-784. Read abstract | Read more

A meta-analysis of rapid (</=60 min) dengue diagnostic assays was conducted to determine accuracy and identify causes of between-study heterogeneity. A systematic review identified 302 potentially suitable studies, of which 11 were selected for meta-analysis. All selected studies evaluated the immunochromatographic test (ICT) manufactured by Panbio Pty Ltd. Individual study results for sensitivity ranged from 0.45 to 1.0, specificity 0.57-1.0, diagnostic odds ratio 4.5-1287, and positive:negative likelihood ratios 2.3-59 and 0.01-0.56, respectively. Results indicated that the ICT evaluated in the selected studies can both rule in and rule out disease but is more accurate when samples are collected later in the acute phase of infection. Limitations of this meta-analysis were significant between-study heterogeneity caused by inconsistencies in evaluation methodologies, and the evaluation of only the Panbio ICT. It is recommended that additional, standardized evaluations are required for other dengue ICTs. Hide abstract

Mayxay M, Thongpraseuth V, Khanthavong M, Lindegårdh N, Barends M, Keola S, Pongvongsa T, Phompida S et al. 2006. An open, randomized comparison of artesunate plus mefloquine vs. dihydroartemisinin-piperaquine for the treatment of uncomplicated Plasmodium falciparum malaria in the Lao People's Democratic Republic (Laos). Trop Med Int Health, 11 (8), pp. 1157-1165. Read abstract | Read more

To determine the efficacy and safety of oral dihydroartemisinin-piperaquine (DP, Artekin) in the treatment of uncomplicated Plasmodium falciparum malaria in southern Laos. Hide abstract

Blacksell SD, Newton PN, Bell D, Kelley J, Mammen MP, Vaughn DW, Wuthiekanun V, Sungkakum A, Nisalak A, Day NP. 2006. The comparative accuracy of 8 commercial rapid immunochromatographic assays for the diagnosis of acute dengue virus infection. Clin Infect Dis, 42 (8), pp. 1127-1134. Read abstract | Read more

The serological diagnosis of acute dengue virus infection relies on the detection of dengue-specific immunoglobulin M (IgM) antibodies. Immunochromatographic tests are rapid diagnostic tests (RDTs) that can be performed at the bedside, but they have not been fully validated for diagnosis of dengue infection. Hide abstract

Phongmany S, Rolain JM, Phetsouvanh R, Blacksell SD, Soukkhaseum V, Rasachack B, Phiasakha K, Soukkhaseum S et al. 2006. Rickettsial infections and fever, Vientiane, Laos. Emerg Infect Dis, 12 (2), pp. 256-262. Read abstract | Read more

Rickettsial diseases have not been described previously from Laos, but in a prospective study, acute rickettsial infection was identified as the cause of fever in 115 (27%) of 427 adults with negative blood cultures admitted to Mahosot Hospital in Vientiane, Laos. The organisms identified by serologic analysis were Orientia tsutsugamushi (14.8%), Rickettsia typhi (9.6%), and spotted fever group rickettsia (2.6% [8 R. helvetica, 1 R. felis, 1 R. conorii subsp. indica, and 1 Rickettsia "AT1"]). Patients with murine typhus had a lower frequency of peripheral lymphadenopathy than those with scrub typhus (3% vs. 46%, p<0.001). Rickettsioses are an underrecognized cause of undifferentiated febrile illnesses among adults in Laos. This finding has implications for the local empiric treatment of fever. Hide abstract

Newton PN, Ward S, Angus BJ, Chierakul W, Dondorp A, Ruangveerayuth R, Silamut K, Teerapong P, Suputtamongkol Y, Looareesuwan S, White NJ. 2006. Early treatment failure in severe malaria resulting from abnormally low plasma quinine concentrations. Trans R Soc Trop Med Hyg, 100 (2), pp. 184-186. Read abstract | Read more

A patient admitted with severe Plasmodium falciparum malaria in western Thailand had an early treatment failure with quinine, despite full dosing. Plasma quinine concentrations were subtherapeutic. Abnormal quinine pharmacokinetics may explain sporadic reports of quinine treatment failures in severe malaria. Hide abstract

Newton PN, McGready R, Fernandez F, Green MD, Sunjio M, Bruneton C, Phanouvong S, Millet P et al. 2006. Manslaughter by fake artesunate in Asia--will Africa be next? PLoS Med, 3 (6), pp. e197. | Read more

Fernández FM, Cody RB, Green MD, Hampton CY, McGready R, Sengaloundeth S, White NJ, Newton PN. 2006. Characterization of solid counterfeit drug samples by desorption electrospray ionization and direct-analysis-in-real-time coupled to time-of-flight mass spectrometry. ChemMedChem, 1 (7), pp. 702-705. Read abstract | Read more

Vacuum is not the limit: direct analysis in real time (DART), a new MS ionization method, allows probing of pharmaceuticals under atmospheric pressure, thus bypassing lengthy sample preparation steps and enhancing throughput. DART allows rapid screening of solid drugs at almost constant temperature which decreases errors in mass measurement and improves the identification of potentially harmful unknowns. This is important for identifying counterfeit drugs (fake hologram shown). © 2006 Wiley-VCH Verlag GmbH & Co. KGaA. Hide abstract

Anderson TJ, Nair S, Sudimack D, Williams JT, Mayxay M, Newton PN, Guthmann JP, Smithuis FM et al. 2005. Geographical distribution of selected and putatively neutral SNPs in Southeast Asian malaria parasites. Mol Biol Evol, 22 (12), pp. 2362-2374. Read abstract | Read more

Loci targeted by directional selection are expected to show elevated geographical population structure relative to neutral loci, and a flurry of recent papers have used this rationale to search for genome regions involved in adaptation. Studies of functional mutations that are known to be under selection are particularly useful for assessing the utility of this approach. Antimalarial drug treatment regimes vary considerably between countries in Southeast Asia selecting for local adaptation at parasite loci underlying resistance. We compared the population structure revealed by 10 nonsynonymous mutations (nonsynonymous single-nucleotide polymorphisms [nsSNPs]) in four loci that are known to be involved in antimalarial drug resistance, with patterns revealed by 10 synonymous mutations (synonymous single-nucleotide polymorphisms [sSNPs]) in housekeeping genes or genes of unknown function in 755 Plasmodium falciparum infections collected from 13 populations in six Southeast Asian countries. Allele frequencies at known nsSNPs underlying resistance varied markedly between locations (F(ST) = 0.18-0.66), with the highest frequencies on the Thailand-Burma border and the lowest frequencies in neighboring Lao PDR. In contrast, we found weak but significant geographic structure (F(ST) = 0-0.14) for 8 of 10 sSNPs. Importantly, all 10 nsSNPs showed significantly higher F(ST) (P < 8 x 10(-5)) than simulated neutral expectations based on observed F(ST) values in the putatively neutral sSNPs. This result was unaffected by the methods used to estimate allele frequencies or the number of populations used in the simulations. Given that dense single-nucleotide polymorphism (SNP) maps and rapid SNP assay methods are now available for P. falciparum, comparing genetic differentiation across the genome may provide a valuable aid to identifying parasite loci underlying local adaptation to drug treatment regimes or other selective forces. However, the high proportion of polymorphic sites that appear to be under balancing selection (or linked to selected sites) in the P. falciparum genome violates the central assumption that selected sites are rare, which complicates identification of outlier loci, and suggests that caution is needed when using this approach. Hide abstract

Newton PN, Day NP, White NJ. 2005. Misattribution of central nervous system dysfunction to artesunate. Clin Infect Dis, 41 (11), pp. 1687-1688. | Read more

Green MD, Vongsack L, Manolin O, Sengaloundeth S, Khounsaknalath L, Pamanivong C, Rojas OV, Newton PN. 2005. Use of a refractometer to assess the quality of antimalarial drugs collected in the Lao Pdr AMERICAN JOURNAL OF TROPICAL MEDICINE AND HYGIENE, 73 (6), pp. 346-346.

Chierakul W, Anunnatsiri S, Short JM, Maharjan B, Mootsikapun P, Simpson AJ, Limmathurotsakul D, Cheng AC et al. 2005. Two randomized controlled trials of ceftazidime alone versus ceftazidime in combination with trimethoprim-sulfamethoxazole for the treatment of severe melioidosis. Clin Infect Dis, 41 (8), pp. 1105-1113. Read abstract | Read more

Two antibiotic regimens are used commonly in Thailand for the initial treatment of severe melioidosis: ceftazidime in combination with trimethoprim-sulfamethoxazole (TMP-SMX) and ceftazidime monotherapy. It is not known whether TMP-SMX provides an additional benefit. Hide abstract

Chaowagul W, Chierakul W, Simpson AJ, Short JM, Stepniewska K, Maharjan B, Rajchanuvong A, Busarawong D et al. 2005. Open-label randomized trial of oral trimethoprim-sulfamethoxazole, doxycycline, and chloramphenicol compared with trimethoprim-sulfamethoxazole and doxycycline for maintenance therapy of melioidosis. Antimicrob Agents Chemother, 49 (10), pp. 4020-4025. Read abstract | Read more

Melioidosis (infection caused by Burkholderia pseudomallei) requires a prolonged course of oral antibiotics following initial intravenous therapy to reduce the risk of relapse after cessation of treatment. The current recommendation is a four-drug regimen (trimethoprim [TMP], sulfamethoxazole [SMX], doxycycline, and chloramphenicol) and a total treatment time of 12 to 20 weeks. Drug side effects are common; the aim of this study was to compare the efficacy and tolerance of the four-drug regimen with a three-drug regimen (TMP-SMX and doxycycline). An open-label, randomized trial was conducted in northeast Thailand. A total of 180 adult Thai patients were enrolled, of which 91 were allocated to the four-drug regimen and 89 to the three-drug regimen. The trial was terminated early due to poor drug tolerance, particularly of the four-drug regimen. The culture-confirmed relapse rates at 1 year were 6.6% and 5.6% for the four- and three-drug regimens, respectively (P = 0.79). The three-drug regimen was better tolerated than the four-drug regimen; 36% of patients receiving four drugs and 19% of patients receiving three drugs required a switch in therapy due to side effects (P = 0.01). The duration of oral therapy was significantly associated with relapse; after adjustment for confounders, patients receiving less than 12 weeks of oral therapy had a 5.7-fold increase of relapse or death. A combination of TMP-SMX and doxycycline is as effective as and better tolerated than the conventional four-drug regimen for the oral treatment phase of melioidosis. Hide abstract

Newton PN, Chung WH, Phetsouvanh R, White NJ. 2005. Sporotrichosis, Plain of Jars, Lao People's Democratic Republic. Emerg Infect Dis, 11 (9), pp. 1496-1497. | Read more

Dondorp AM, Desakorn V, Pongtavornpinyo W, Sahassananda D, Silamut K, Chotivanich K, Newton PN, Pitisuttithum P, Smithyman AM, White NJ, Day NP. 2005. Estimation of the total parasite biomass in acute falciparum malaria from plasma PfHRP2. PLoS Med, 2 (8), pp. e204. Read abstract | Read more

In falciparum malaria sequestration of erythrocytes containing mature forms of Plasmodium falciparum in the microvasculature of vital organs is central to pathology, but quantitation of this hidden sequestered parasite load in vivo has not previously been possible. The peripheral blood parasite count measures only the circulating, relatively non-pathogenic parasite numbers. P. falciparum releases a specific histidine-rich protein (PfHRP2) into plasma. Quantitative measurement of plasma PfHRP2 concentrations may reflect the total parasite biomass in falciparum malaria. Hide abstract

Nash D, Nair S, Mayxay M, Newton PN, Guthmann JP, Nosten F, Anderson TJ. 2005. Selection strength and hitchhiking around two anti-malarial resistance genes. Proc Biol Sci, 272 (1568), pp. 1153-1161. Read abstract | Read more

Neutral mutations may hitchhike to high frequency when they are situated close to sites under positive selection, generating local reductions in genetic diversity. This process is thought to be an important determinant of levels of genomic variation in natural populations. The size of genome regions affected by genetic hitchhiking is expected to be dependent on the strength of selection, but there is little empirical data supporting this prediction. Here, we compare microsatellite variation around two drug resistance genes (chloroquine resistance transporter (pfcrt), chromosome 7, and dihydrofolate reductase (dhfr), chromosome 4) in malaria parasite populations exposed to strong (Thailand) or weak selection (Laos) by anti-malarial drugs. In each population, we examined the point mutations underlying resistance and length variation at 22 (chromosome 4) or 25 (chromosome 7) microsatellite markers across these chromosomes. All parasites from Thailand carried the K76T mutation in pfcrt conferring resistance to chloroquine (CQ) and 2-4 mutations in dhfr conferring resistance to pyrimethamine. By contrast, we found both wild-type and resistant alleles at both genes in Laos. There were dramatic differences in the extent of hitchhiking in the two countries. The size of genome regions affected was smaller in Laos than in Thailand. We observed significant reduction in variation relative to sensitive parasites for 34-64 kb (2-4 cM) in Laos on chromosome 4, compared with 98-137 kb (6-8 cM) in Thailand. Similarly, on chromosome 7, we observed reduced variation for 34-69 kb (2-4 cM) around pfcrt in Laos, but for 195-268 kb (11-16 cM) in Thailand. Reduction in genetic variation was also less extreme in Laos than in Thailand. Most loci were monomorphic in a 12 kb region surrounding both genes on resistant chromosomes from Thailand, whereas in Laos, even loci immediately proximal to selective sites showed some variation on resistant chromosomes. Finally, linkage disequilibrium (LD) decayed more rapidly around resistant pfcrt and dhfr alleles from Laos than from Thailand. These results demonstrate that different realizations of the same selective sweeps may vary considerably in size and shape, in a manner broadly consistent with selection history. From a practical perspective, genomic regions containing resistance genes may be most effectively located by genome-wide association in populations exposed to strong drug selection. However, the lower levels of LD surrounding resistance alleles in populations under weak selection may simplify identification of functional mutations. Hide abstract

Phongmany S, Phetsouvanh R, Sisouphone S, Darasavath C, Vongphachane P, Rattanavong O, Mayxay M, Ramsay AC et al. 2005. A randomized comparison of oral chloramphenicol versus ofloxacin in the treatment of uncomplicated typhoid fever in Laos. Trans R Soc Trop Med Hyg, 99 (6), pp. 451-458. Read abstract | Read more

We conducted a randomized open trial of oral chloramphenicol (50mg/kg/day in four divided doses for 14 days) versus ofloxacin (15 mg/kg/day in two divided doses for 3 days) in 50 adults with culture-confirmed uncomplicated typhoid fever in Vientiane, Laos. Patients had been ill for a median (range) of 8 (2-30) days. All Salmonella enterica serotype typhi isolates were nalidixic acid-sensitive, four (8%) were chloramphenicol-resistant and three (6%) were multidrug-resistant. Median (range) fever clearance times were 90 (24-224) hours in the chloramphenicol group and 54 (6-93) hours in the ofloxacin group (P<0.001). One patient in the chloramphenicol group developed an ileal perforation. Three days ofloxacin was more effective than 14 days chloramphenicol for the in-patient treatment of typhoid fever, irrespective of antibiotic susceptibility, and was of similar cost. Hide abstract

Newton PN, Chaulet JF, Brockman A, Chierakul W, Dondorp A, Ruangveerayuth R, Looareesuwan S, Mounier C, White NJ. 2005. Pharmacokinetics of oral doxycycline during combination treatment of severe falciparum malaria. Antimicrob Agents Chemother, 49 (4), pp. 1622-1625. Read abstract | Read more

The pharmacokinetics of oral doxycycline administered at 200 mg every 24 h were investigated in 17 patients recovering from severe Plasmodium falciparum malaria. The data suggest that the doses of doxycycline currently recommended (circa 3.5 mg/kg of body weight daily) may not be optimal. Hide abstract

Cockburn R, Newton PN, Agyarko EK, Akunyili D, White NJ. 2005. The global threat of counterfeit drugs: Why industry and governments must communicate the dangers PLOS MEDICINE, 2 (4), pp. 302-308. | Read more

Dondorp AM, Newton PN, Mayxay M, Van Damme W, Smithuis FM, Yeung S, Petit A, Lynam AJ et al. 2004. Fake antimalarials in Southeast Asia are a major impediment to malaria control: multinational cross-sectional survey on the prevalence of fake antimalarials. Trop Med Int Health, 9 (12), pp. 1241-1246. Read abstract | Read more

To assess the prevalence of counterfeit antimalarial drugs in Southeast (SE) Asia. Hide abstract

Mayxay M, Khanthavong M, Lindegårdh N, Keola S, Barends M, Pongvongsa T, Yapom R, Annerberg A et al. 2004. Randomized comparison of chloroquine plus sulfadoxine-pyrimethamine versus artesunate plus mefloquine versus artemether-lumefantrine in the treatment of uncomplicated falciparum malaria in the Lao People's Democratic Republic. Clin Infect Dis, 39 (8), pp. 1139-1147. Read abstract | Read more

Recent clinical trials in the Lao People's Democratic Republic have demonstrated that chloroquine and sulfadoxine-pyrimethamine, which are national malaria treatment policy, are no longer effective in the treatment of uncomplicated Plasmodium falciparum malaria. Hide abstract

Mayxay M, Pukrittayakamee S, Newton PN, White NJ. 2004. Mixed-species malaria infections in humans. Trends Parasitol, 20 (5), pp. 233-240. Read abstract | Read more

Mixed-species malaria infections are often not recognized or underestimated. In Asia, surveys usually report that <2% of infections are mixed, whereas therapeutic studies in vivax or falciparum malaria have demonstrated a high prevalence (up to 30%) of infection with the other malaria species during convalescence, suggesting covert co-infection. In epidemiological studies, a high prevalence of cryptic mixed-malaria species infection has been detected by sensitive PCR techniques. Concurrently infecting malaria species are mutually suppressive with Plasmodium falciparum tending to dominate Plasmodium vivax, but P. vivax attenuating the severity of P. falciparum. There is evidence for some cross-species immunity. These interactions have important clinical and public health implications. Hide abstract

Mayxay M, Newton PN, Khanthavong M, Tiengkham P, Phetsouvanh R, Phompida S, Brockman A, White NJ. 2004. Monitoring antimalarial drug efficacy - Reply CLINICAL INFECTIOUS DISEASES, 38 (8), pp. 1193-1194. | Read more

Chotivanich K, Udomsangpetch R, Chierakul W, Newton PN, Ruangveerayuth R, Pukrittayakamee S, Looareesuwan S, White NJ. 2004. In vitro efficacy of antimalarial drugs against Plasmodium vivax on the western border of Thailand. Am J Trop Med Hyg, 70 (4), pp. 395-397. Read abstract

The susceptibility of 20 isolates of Plasmodium vivax on the Thailand-Myanmar border to seven antimalarial drugs was evaluated using the schizont maturation inhibition technique. The geometric mean 50% inhibition concentration (IC(50)) values were quinine = 308 ng/mL, amodiaquine =14 ng/mL, chloroquine =50 ng/mL, mefloquine = 127 ng/mL, sulfadoxine/pyrimethamine (80:1) = 800/10 ng/mL, pyrimethamine = 8 ng/mL, and artesunate = 0.5 ng/mL. Compared with P. falciparum in this area, P. vivax was more sensitive to chloroquine and artesunate, equally sensitive to quinine, and more resistant to mefloquine. Hide abstract

Chotivanich K, Sritabal J, Udomsangpetch R, Newton P, Stepniewska KA, Ruangveerayuth R, Looareesuwan S, Roberts DJ, White NJ. 2004. Platelet-induced autoagglutination of Plasmodium falciparum-infected red blood cells and disease severity in Thailand. J Infect Dis, 189 (6), pp. 1052-1055. Read abstract | Read more

The relationship of the platelet-mediated autoagglutination of Plasmodium falciparum-infected red blood cells (IRBCs) to disease severity was investigated in 182 Thai patients with falciparum malaria; it was evident in 43% of uncomplicated malaria (n=63), 41% of severe malaria (n=104), and 100% of cerebral malaria (n=15; P=.001) isolates. The median (range) number of IRBCs in agglutinates per 1000 IRBCs was significantly higher in cerebral malaria (6 [3-42]) than in severe (0 [0-52]) and uncomplicated (0 [0-24]) malaria (P=.01). In multivariate analyses, high parasitemia and cerebral malaria were associated independently with parasite agglutination. Hide abstract

Mayxay M, Newton PN, Yeung S, Pongvongsa T, Phompida S, Phetsouvanh R, White NJ. 2004. Short communication: An assessment of the use of malaria rapid tests by village health volunteers in rural Laos. Trop Med Int Health, 9 (3), pp. 325-329. Read abstract | Read more

Rapid malaria diagnosis, a key component of malaria control strategies, is hampered by the expense and training requirements of reliable microscopy. Rapid malaria antigen tests may improve the diagnosis of malaria in the rural tropics. After 1 h training 64 village health volunteers (VHVs) from rural Laos, with no previous laboratory experience, performed two malaria rapid diagnostic tests (ParacheckPf and OptiMAL) accurately. The reliability of six VHVs was assessed longitudinally, over 10 months with different frequencies of retraining. Compared with microscopy, error rates in dipstick interpretation were low (<2%) for both tests and were not associated with retraining frequency (P>0.2). Previously untrained Lao VHVs performed malaria rapid tests reliably with high sensitivity and specificity after minimal training. Hide abstract

Silamut K, Newton PN, Teja-Isavadharm P, Suputtamongkol Y, Siriyanonda D, Rasameesoraj M, Pukrittayakamee S, White NJ. 2003. Artemether bioavailability after oral or intramuscular administration in uncomplicated falciparum malaria. Antimicrob Agents Chemother, 47 (12), pp. 3795-3798. Read abstract | Read more

The antimalarial activity of artemether following oral or intramuscular administration in the plasma of 15 adults with acute uncomplicated Plasmodium falciparum malaria was measured by bioassay. The peak concentrations in plasma following oral administration were higher in patients with acute illness (median, 1,905 mmol of dihydroartemisinin [DHA] equivalents per liter; range, 955 to 3,358 mmol of DHA equivalents per liter) than in patients in the convalescent phase (median, 955 mmol of DHA equivalents per liter; range, 576 to 1,363 mmol of DHA equivalents per liter), and clearance (CL/F) was lower in patients in the acute phase (1.11 liters/kg/h; range, 0.21 to 3.08 liters/kg/h) than in patients in the convalescent phase (median, 2.76 liters/kg/h; range, 1.56 to 5.74 liters/kg/h) (P< or =0.008). Antimalarial activity in terms of the peak concentration in plasma (Cmax) after oral administration was a median of 16 times higher than that after intramuscular administration. The ratio of the area under the plasma concentration-time curve during the first 24 h (AUC(0-24)) after oral administration of artemether to the AUC(0-24) after intramuscular administration was a median of 3.3 (range, 1 to 11) (P=0.0001). In the acute phase, the time to Cmax was significantly shorter after oral administration (median, 1 h; range, 0.5 to 3.0 h) than after intramuscular administration (median, 8 h; range, 4 to 24 h) (P=0.001). Intramuscular artemether is absorbed very slowly in patients with acute malaria. Hide abstract

Mayxay M, Newton PN, Khanthavong M, Tiengkham P, Phetsouvanh R, Phompida S, Brockman A, White NJ. 2003. Chloroquine versus sulfadoxine-pyrimethamine for treatment of Plasmodium falciparum malaria in Savannakhet Province, Lao People's Democratic Republic: an assessment of national antimalarial drug recommendations. Clin Infect Dis, 37 (8), pp. 1021-1028. Read abstract | Read more

The in vivo efficacies of the Lao People's Democratic Republic (Laos) nationally recommended antimalarial agents--chloroquine and sulfadoxine-pyrimethamine-were assessed in a randomized, comparative trial that involved 100 patients with uncomplicated Plasmodium falciparum malaria who were followed for 42 days after starting treatment. Despite a shorter mean time to fever clearance associated with administration of chloroquine (mean time to clearance, 35.6 h; 95% confidence interval [CI], 26.3-45.0 h), compared with that associated with sulfadoxine-pyrimethamine (61.1 h; 95% CI, 50.9-71.3 h; P<.001), treatment failures were twice as frequent among patients receiving chloroquine therapy than among those receiving sulfadoxine-pyrimethamine therapy (36% vs. 18%; P=.02). Of 23 treatment failures, 10 (43%) were high grade. Treatment failure rates among children (age range, 5-15 years) were 4.9 times higher (95% CI, 2-12) than those among adults (P<.0001). Gametocytemia after antimalarial treatment was associated with receipt of sulfadoxine-pyrimethamine therapy and with treatment failure (P=.009). The efficacy of both chloroquine and sulfadoxine-pyrimethamine in Laos is unsatisfactory. Hide abstract

Nair S, Williams JT, Brockman A, Paiphun L, Mayxay M, Newton PN, Guthmann JP, Smithuis FM et al. 2003. A selective sweep driven by pyrimethamine treatment in southeast asian malaria parasites. Mol Biol Evol, 20 (9), pp. 1526-1536. Read abstract | Read more

Malaria parasites (Plasmodium falciparum) provide an excellent system in which to study the genomic effects of strong selection in a recombining eukaryote because the rapid spread of resistance to multiple drugs during the last the past 50 years has been well documented, the full genome sequence and a microsatellite map are now available, and haplotype data can be easily generated. We examined microsatellite variation around the dihydrofolate reductase (dhfr) gene on chromosome 4 of P. falciparum. Point mutations in dhfr are known to be responsible for resistance to the antimalarial drug pyrimethamine, and resistance to this drug has spread rapidly in Southeast (SE) Asia after its introduction in 1970s. We genotyped 33 microsatellite markers distributed across chromosome 4 in 61 parasites from a location on the Thailand/Myanmar border. We observed minimal microsatellite length variation in a 12-kb (0.7-cM) region flanking the dhfr gene and diminished variation for approximately 100 kb (6 cM), indicative of a single origin of resistant alleles. Furthermore, we found the same or similar microsatellite haplotypes flanked resistant dhfr alleles sampled from 11 parasite populations in five SE Asian countries indicating recent invasion of a single lineage of resistant dhfr alleles in locations 2000 km apart. Three features of these data are of especially interest. (1). Pyrimethamine resistance is generally assumed to have evolved multiple times because the genetic basis is simple and resistance can be selected easily in the laboratory. Yet our data clearly indicate a single origin of resistant dhfr alleles sampled over a large region of SE Asia. (2). The wide valley ( approximately 6 cM) of reduced variation around dhfr provides "proof-of-principle" that genome-wide association may be an effective way to locate genes under strong recent selection. (3). The width of the selective valley is consistent with predictions based on independent measures of recombination, mutation, and selection intensity, suggesting that we have reasonable estimates of these parameters. We conclude that scanning the malaria parasite genome for evidence of recent selection may prove an extremely effective way to locate genes underlying recently evolved traits such as drug resistance, as well as providing an opportunity to study the dynamics of selective events that have occurred recently or are currently in progress. Hide abstract

Soukaloun D, Kounnavong S, Pengdy B, Boupha B, Durondej S, Olness K, Newton PN, White NJ. 2003. Dietary and socio-economic factors associated with beriberi in breastfed Lao infants ANNALS OF TROPICAL PAEDIATRICS, 23 (3), pp. 181-186. Read abstract | Read more

A case-control study was conducted to investigate the dietary and socio-economic factors associated with beriberi in infants attending three public hospitals in Vientiane, Lao PDR. Forty-three breast-feeding infants with a median (range) age of 3 (1-9) months were admitted with beriberi. This was defined as the presence of signs of congestive heart failure or shock in the absence of fever or other signs of sepsis, hypovolaemia or cardiac abnormalities, with rapid clinical improvement following parenteral thiamine. Subjects were matched by age and diet to 43 breast-feeding healthy control infants. Compared with control mothers, mothers of infants with beriberi had significantly less diet diversity (p < 0.001), soaked glutinous rice for significantly longer or were more likely to pour off excess water from non-glutinous rice (p = 0.006), had fewer years of schooling (p < 0.05), were more likely to report that income was inadequate for basic needs (p < 0.001), to perform hard physical labour (p < 0.01) and to be married to farmers (p < 0.01). Clinically significant thiamine deficiency in breastfed infants in Lao relates to methods of preparing rice, the food selected by lactating mothers and the family's socio-economic status. Hide abstract

Newton PN, Dondorp A, Green M, Mayxay M, White NJ. 2003. Counterfeit artesunate antimalarials in southeast Asia. Lancet, 362 (9378), pp. 169. | Read more

Newton PN, Angus BJ, Chierakul W, Dondorp A, Ruangveerayuth R, Silamut K, Teerapong P, Suputtamongkol Y, Looareesuwan S, White NJ. 2003. Randomized comparison of artesunate and quinine in the treatment of severe falciparum malaria. Clin Infect Dis, 37 (1), pp. 7-16. Read abstract | Read more

A randomized, open-label comparison of artesunate and quinine was conducted in 113 adults with clinically severe falciparum malaria in western Thailand. Mortality was 12% with artesunate and 22% with quinine treatment (relative risk, 0.53; 95% confidence interval, 0.23-1.26; P=.22). Multiple logistic regression analysis found admission plasma lactate level, Glasgow Coma Scale score, and total serum bilirubin level to be independent risk factors for death. Coma recovery and times to normalize plasma lactate levels were similar, but the parasite clearance time was much shorter among artesunate-treated patients (P=.019). Fewer patients became hypoglycemic during artesunate therapy (10%) than during quinine therapy (28%) (P=.03). Artesunate is at least as effective as quinine in the treatment of adults with severe malaria. Larger trials are required to determine whether mortality is reduced among patients treated with artesunate. Hide abstract

Mayxay M, Phetsouvanh R, Phompida S, Newton PN, Khanthavong M, Vannachone B, Brockmans A, White NJ. 2003. A randomized comparison of oral chloroquine and sulfadoxine-pyrimethamine for the treatment of uncomplicated Plasmodium falciparum malaria in Laos. Trans R Soc Trop Med Hyg, 97 (3), pp. 343-344. Read abstract | Read more

Between June and October 2000 we conducted the first randomized trial in Laos comparing chloroquine (CQ) with sulfadoxine-pyrimethamine (SP) in the treatment of uncomplicated Plasmodium falciparum malaria (n = 29, 42-d follow-up, age > 5 years). The proportion of patients with treatment failure was high (CQ = 78%, RIII 46%; SP = 36%, RIII 15%). The treatment policy for uncomplicated P. falciparum malaria in Laos needs to be reviewed urgently. Hide abstract

Simpson AJ, Newton PN, Chierakul W, Chaowagul W, White NJ. 2003. Diabetes mellitus, insulin, and melioidosis in Thailand. Clin Infect Dis, 36 (5), pp. e71-e72. Read abstract | Read more

A review of case records for 1817 Thai patients with melioidosis revealed that <10% of the 382 patients with diabetes mellitus were insulin dependent. This provides evidence against the hypothesis that insulin deficiency contributes to the known susceptibility to melioidosis in patients with diabetes mellitus. Hide abstract

Newton PN, Wakefield AE, Goldin R, Govan J. 2003. Pneumocystis carinii pneumonia with pleurisy, platypnoea and orthodeoxia. Thorax, 58 (2), pp. 185-186. Read abstract | Read more

We present a patient who collapsed with chest pain and dyspnoea on a transatlantic flight. She was found to have Pneumocystis carinii pneumonia (PCP) and human immunodeficiency virus infection. Platypnoea and orthodeoxia, which have not been previously reported in association with PCP, were major features of her illness. The PCP predominantly affected her lung bases and it is likely that gravity increased intrapulmonary blood flow through poorly ventilated lung bases with failure of pulmonary vasoconstriction to increase upper zone perfusion, exacerbating desaturation on sitting up. The partial DNA sequence of the infecting P carinii was identical to previously described isolates. Hide abstract

Newton PN, Chierakul W, Ruangveerayuth R, Abhigantaphand D, Looareesuwan S, White NJ. 2003. Malaria and amphetamine 'horse tablets' in Thailand. Trop Med Int Health, 8 (1), pp. 17-18. Read abstract | Read more

During recent clinical malaria research in Thailand we found a high frequency of amphetamine misuse and withdrawal amongst patients admitted to hospital with Plasmodium falciparum malaria. This comorbidity may cause diagnostic confusion, alter malaria pathophysiology and lead to drug interactions. Hide abstract

Newton PN, Thai LEH, Tip NQ, Short JM, Chierakul W, Rajanuwong A, Pitisuttithum P, Chasombat S et al. 2002. A randomized, double-blind, placebo-controlled trial of acetazolamide for the treatment of elevated intracranial pressure in cryptococcal meningitis. Clin Infect Dis, 35 (6), pp. 769-772. Read abstract | Read more

We conducted a trial of oral acetazolamide for the treatment of cryptococcal meningitis in 22 Thai adults with headache and an opening cerebrospinal fluid pressure of >/=200 mm H(2)0. The trial was terminated prematurely because patients who received acetazolamide developed significantly lower venous bicarbonate levels and higher chloride levels and had more-frequent serious adverse events than did subjects who received placebo. Hide abstract

Newton PN, Michelson G, Ruangveerayuth R, White NJ. 2002. Retinal haemorrhage in P falciparum malaria. Lancet, 360 (9332), pp. 515. | Read more

Chotivanich K, Udomsangpetch R, McGready R, Proux S, Newton P, Pukrittayakamee S, Looareesuwan S, White NJ. 2002. Central role of the spleen in malaria parasite clearance. J Infect Dis, 185 (10), pp. 1538-1541. Read abstract | Read more

In acute malaria, red blood cells (RBCs) that have been parasitized, but no longer contain a malaria parasite, are found in the circulation (ring-infected erythrocyte surface antigen [RESA]-RBCs). These are thought to arise by splenic removal of dead or damaged intraerythrocytic parasites and return of the intact RBCs to the circulation. In a study of 5 patients with acute falciparum malaria who had previously undergone splenectomy, it was found that none of these 5 patients had any circulating RESA-RBCs, in contrast to the uniform finding of RESA-RBCs in all patients with acute malaria and intact spleens. Parasite clearance after artesunate treatment was markedly prolonged, although the parasites appeared to be dead and could not be cultured ex vivo. These observations confirm the central role of the spleen in the clearance of parasitized RBCs after antimalarial treatment with an artemisinin derivative. Current criteria for high-grade antimalarial drug resistance that are based on changes in parasitemia are not appropriate for asplenic patients. Hide abstract

Newton PN, White NJ, Rozendaal JA, Green MD. 2002. Murder by fake drugs. BMJ, 324 (7341), pp. 800-801. | Read more

Newton PN, van Vugt M, Teja-Isavadharm P, Siriyanonda D, Rasameesoroj M, Teerapong P, Ruangveerayuth R, Slight T et al. 2002. Comparison of oral artesunate and dihydroartemisinin antimalarial bioavailabilities in acute falciparum malaria. Antimicrob Agents Chemother, 46 (4), pp. 1125-1127. Read abstract | Read more

Plasma antimalarial activity following oral artesunate or dihydroartemisinin (DHA) treatment was measured by a bioassay in 18 patients with uncomplicated falciparum malaria. The mean antimalarial activity in terms of the bioavailability of DHA relative to that of artesunate did not differ significantly from 1, suggesting that DHA can be formulated to be an acceptable oral alternative to artesunate. Hide abstract

Newton PN. 2002. Bird notes from the Siang River Valley, Arunachal Pradesh, India Forktail, 18 pp. 156-157.

Suputtamongkol Y, Newton PN, Angus B, Teja-Isavadharm P, Keeratithakul D, Rasameesoraj M, Pukrittayakamee S, White NJ. 2001. A comparison of oral artesunate and artemether antimalarial bioactivities in acute falciparum malaria. Br J Clin Pharmacol, 52 (6), pp. 655-661. Read abstract | Read more

Artesunate and artemether are the two most widely used artemisinin derivatives in the treatment of uncomplicated Plasmodium falciparum malaria, but there is little information on their comparative pharmacokinetics. The aim of this study was to examine the relative oral antimalarial bioavailability and pharmacokinetics of the two derivatives. Hide abstract

Mayxay M, Chotivanich K, Pukrittayakamee S, Newton P, Looareesuwan S, White NJ. 2001. Contribution of humoral immunity to the therapeutic response in falciparum malaria. Am J Trop Med Hyg, 65 (6), pp. 918-923. Read abstract

The contribution of humoral immunity to the therapeutic response in acute falciparum malaria was assessed in a case-control study. Forty adult Thai patients with acute falciparum malaria who had subsequent recrudescent infections and 40 patients matched for age, therapeutic regimen, and disease severity who were cured by Day 28 were studied. All cured patients had positive immunoglobulin (Ig) G to ring-infected erythrocyte surface antigen (RESA) in their admission plasma, compared with only 60% of patients who failed to respond to treatment (P < 0.001). The proportion of IgM-positive cases at admission was also higher in the successfully treated group than in the group with failure (70% versus 30%) (P < 0.001). The geometric mean (95% confidence interval) reciprocal IgG titer at admission was significantly higher in cured patients (187.0 [83.5-418.3]) compared with those who experienced treatment failure (11.6 [5.1-26.5]) (P < 0.001). The patients with uncomplicated malaria who were both IgG and IgM positive at admission had significantly shorter fever clearance times and lower admission parasitemia levels compared with those who were negative (P = 0.01 and P = 0.02, respectively). The median (range) in vitro parasite multiplication rate was significantly lower in cultures containing positive anti-RESA antibody plasma compared with those containing normal plasma (0.7 [0.1-3.5] versus 2.6 [0.1-12.1]; P < 0.001). These results suggest that antimalarial antibodies may play an important supportive role in the therapeutic response to antimalarial drugs during acute falciparum malaria. Hide abstract

Newton PN, Chierakul W, Ruangveerayuth R, Silamut K, Teerapong P, Krudsood S, Looareesuwan S, White NJ. 2001. A comparison of artesunate alone with combined artesunate and quinine in the parenteral treatment of acute falciparum malaria. Trans R Soc Trop Med Hyg, 95 (5), pp. 519-523. Read abstract | Read more

In some areas clinicians have combined parenteral artesunate and quinine in the belief that the 2 drugs would be additive or synergistic in severe malaria. A randomized comparison of the effectiveness of intravenous (i.v.) artesunate versus i.v. artesunate and i.v. quinine together on parasite clearance was conducted in 1998/99 amongst 69 patients with uncomplicated and severe Plasmodium falciparum malaria in western Thailand. The parasite clearance time did not differ significantly between the 2 treatment groups (P = 0.12), but adverse events were significantly more frequent in the artesunate plus quinine group (P = 0.05). Quinine did not have a significant antipyretic effect and artesunate did not affect the electrocardiographic QTc interval. There is no benefit evident from combining parenteral administration of these 2 antimalarial drugs in the acute phase of treatment. Hide abstract

Newton PN, Chotivanich K, Chierakul W, Ruangveerayuth R, Teerapong P, Silamut K, Looareesuwan S, White NJ. 2001. A comparison of the in vivo kinetics of Plasmodium falciparum ring-infected erythrocyte surface antigen-positive and -negative erythrocytes. Blood, 98 (2), pp. 450-457. Read abstract | Read more

Ring-infected erythrocyte surface antigen (RESA)-positive, Plasmodium falciparum-negative red blood cells (RBCs) are cells from which the malaria parasite has been removed by the host without the destruction of the erythrocyte ("pitting"). The survival of RESA-RBCs in vivo was assessed in 14 severe and 6 uncomplicated falciparum malaria patients. The mean RESA-RBC life of 183 hours (95% confidence interval [CI], 136-246) was longer than the median parasite clearance time of 66 hours (range, 30-108 hours) but shorter than the mean red cell life of 1027 hours (95% CI, 840-1213) (P =.0004), with a median ratio of 0.2:1.0 (range, 0.1-0.7). The estimated median percentage of parasites pitted/body transit was 0.003% (range, 0.001%-0.05%). The rate of rise of the RESA-RBC count during the first 24 hours after antimalarial treatment was significantly faster (P =.036) and the subsequent RESA-RBC survival significantly shorter (P =.017) after treatment with an artemisinin derivative than after treatment with quinine. Parasitization of red cells leads to changes in the erythrocyte that shorten their survival even if the parasite is removed subsequently. Hide abstract

Newton P, Proux S, Green M, Smithuis F, Rozendaal J, Prakongpan S, Chotivanich K, Mayxay M et al. 2001. Fake artesunate in southeast Asia. Lancet, 357 (9272), pp. 1948-1950. Read abstract | Read more

Artesunate is a key antimalarial drug in the treatment of multidrug-resistant Plasmodium falciparum malaria in southeast Asia. We investigated the distribution of counterfeit artesunate tablets by use of the validated, simple, and inexpensive Fast Red TR dye technique. We also aimed to identify distinguishing characteristics of the fake drugs. Of 104 shop-bought "artesunate" samples from Cambodia, Laos, Myanmar (Burma), Thailand, and Vietnam, 38% did not contain artesunate. Characteristics such as cost and physical appearance of the tablets and packaging reliably predicted authenticity. The illicit trade in counterfeit antimalarials is a great threat to the lives of patients with malaria. The dye test will assist national malaria control authorities in urgently needed campaigns to stop this murderous trade. Hide abstract

Newton P, Simpson A, Wanwimolruk S, Maliakal P, Villegas L, Kuypers D, White NJ. 2001. Oral quinine pharmacokinetics and dietary salt intake. Eur J Clin Pharmacol, 57 (2), pp. 111-113. Read abstract | Read more

The objective was to determine whether or not dietary salt intake affects the relative bioavailability of oral quinine. Salt intake has been shown to alter quinidine bioavailability. Hide abstract

Phetsouvanh R, Phongmany S, Newton P, Mayxay M, Ramsay A, Wuthiekanun V, White NJ. 2001. Melioidosis and Pandora's box in the Lao People's Democratic Republic. Clin Infect Dis, 32 (4), pp. 653-654. Read abstract | Read more

Melioidosis has not been recognized previously in Laos, but within months of starting a prospective study of community acquired septicemia in Vientiane, 2 patients with melioidosis were identified. One was a previously healthy, 44-year-old female rice farmer who presented with supraclavicular lymphadenitis and the other was a 74-year-old man with diabetes and renal calculi who was receiving corticosteroids and had septicemia and septic arthritis. Hide abstract

Newton P, Simpson A, Wanwimolruk S, Maliakal P, Villegas L, Kuypers D, White NJ. 2001. Oral quinine pharmacokinetics and dietary salt intake Eur J Clin Pharmacol, 57 (2), pp. 111-113. Read abstract

OBJECTIVES: The objective was to determine whether or not dietary salt intake affects the relative bioavailability of oral quinine. Salt intake has been shown to alter quinidine bioavailability. METHODS: The pharmacokinetic properties of oral quinine sulphate (600 mg salt) were investigated in seven healthy Caucasian volunteers, in a randomised, crossover study, on low- and high-salt diets. Plasma quinine concentrations were measured by high-performance liquid chromatography (HPLC) and the 24-h urinary sodium excretion was assayed. RESULTS: Although the 24-h urine sodium excretion was significantly higher when the volunteers were on a high-salt diet, there were no significant differences in quinine AUC0-infinity, tmax, and Cmax after the two diets. The median (range) quinine elimination half-life was significantly shorter after a high-salt diet [8.5 (4.3-10.2) h] than after a low-salt diet [10.0 (7.6-14.8) h] (P = 0.04). CONCLUSION: Dietary salt does not affect the relative oral bioavailability of quinine sulphate. Hide abstract

Chotivanich K, Udomsangpetch R, Simpson JA, Newton P, Pukrittayakamee S, Looareesuwan S, White NJ. 2000. Parasite multiplication potential and the severity of Falciparum malaria. J Infect Dis, 181 (3), pp. 1206-1209. Read abstract | Read more

The multiplication rates and invasiveness of Plasmodium falciparum parasites isolated from adult Thai patients hospitalized with uncomplicated malaria (n=34) were compared with those from persons with severe malaria (n=42). To simulate severe malaria and control for host effects, the in vitro cultures were adjusted to 1% parasitemia and used the same red blood cell donor. P. falciparum isolates from persons with severe malaria had initial cycle multiplication rates in vitro that were 3-fold higher than those from uncomplicated malaria (median [95% confidence interval], 8.3 [7. 1-10.5] vs. 2.8 [1.7-3.9]; P=.001). Parasites causing severe malaria exhibited unrestricted red blood cell invasion, whereas those from uncomplicated malaria were restricted to a geometric mean of 40 (31%-53%) of red blood cells. P. falciparum parasites causing severe malaria were less selective and multiplied more at high parasitemias than those causing uncomplicated malaria. Hide abstract

Chotivanich K, Udomsangpetch R, Simpson JA, Newton P, Pukrittayakamee S, Looareesuwan S, White NJ. 2000. Parasite multiplication potential and the severity of Falciparum malaria J Infect Dis, 181 (3), pp. 1206-1209. Read abstract

The multiplication rates and invasiveness of Plasmodium falciparum parasites isolated from adult Thai patients hospitalized with uncomplicated malaria (n=34) were compared with those from persons with severe malaria (n=42). To simulate severe malaria and control for host effects, the in vitro cultures were adjusted to 1% parasitemia and used the same red blood cell donor. P. falciparum isolates from persons with severe malaria had initial cycle multiplication rates in vitro that were 3-fold higher than those from uncomplicated malaria (median [95% confidence interval], 8.3 [7. 1-10.5] vs. 2.8 [1.7-3.9]; P=.001). Parasites causing severe malaria exhibited unrestricted red blood cell invasion, whereas those from uncomplicated malaria were restricted to a geometric mean of 40 (31%-53%) of red blood cells. P. falciparum parasites causing severe malaria were less selective and multiplied more at high parasitemias than those causing uncomplicated malaria. Hide abstract

Newton P, Suputtamongkol Y, Teja-Isavadharm P, Pukrittayakamee S, Navaratnam V, Bates I, White N. 2000. Antimalarial bioavailability and disposition of artesunate in acute falciparum malaria. Antimicrob Agents Chemother, 44 (4), pp. 972-977. Read abstract | Read more

The pharmacokinetic properties of oral and intravenous artesunate (2 mg/kg of body weight) were studied in 19 adult patients with acute uncomplicated Plasmodium falciparum malaria by using a randomized crossover design. A sensitive bioassay was used to measure the antimalarial activity in plasma which results from artesunate and its principal metabolite, dihydroartemisinin. The oral study was repeated with 15 patients during convalescence. The mean absolute oral bioavailability of the antimalarial agent in patients with acute malaria was 61% (95% confidence interval [CI], 52 to 70%). The absorption and elimination of oral artesunate were rapid, with a mean elimination half-life of antimalarial activity of 43 min (95% CI, 33 to 53 min). Following oral administration to patients with acute falciparum malaria, peak antimalarial activity in plasma and the area under the plasma concentration-time curve were approximately double those during convalescence and the apparent volume of distribution and clearance were approximately half those during convalescence (P < or = 0.005). Acute malaria is associated with a significant reduction in the clearance of artesunate-associated antimalarial activity. Hide abstract

Newton P, Keeratithakul D, Teja-Isavadharm P, Pukrittayakamee S, Kyle D, White N. 1999. Pharmacokinetics of quinine and 3-hydroxyquinine in severe falciparum malaria with acute renal failure. Trans R Soc Trop Med Hyg, 93 (1), pp. 69-72. Read abstract | Read more

The plasma concentrations of quinine and its main metabolite, 3-hydroxyquinine (3OHQn), were measured in 5 adult Thai patients with severe Plasmodium falciparum malaria and acute renal failure. Two patients required peritoneal dialysis but all survived. During acute renal failure plasma concentrations of 3OHQn rose to reach up to 45% of the levels of the parent compound. The estimated median (range) quinine clearance was 0.83 mL/kg/min (0.58-1.16), and 3OHQn clearance/fraction of quinine converted was 3.40 mL/kg/min (2.58-4.47). The estimated 3OHQn terminal elimination half-life was 21 h (16.5-32.5). These data suggest that 3OHQn contributes about 12% of the antimalarial activity of the parent compound in patients with falciparum malaria and acute renal failure. It is also likely that 3OHQn contributes to adverse effects, although this metabolite is not quantitated routinely by current high-performance liquid chromatography quinine assays. Hide abstract

Newton P, Standing SJ, Kay JD, Hart G. 1999. Alcoholic ketoacidosis as the cause of repeated episodes of severe metabolic acidosis. Ann Clin Biochem, 36 ( Pt 6) (6), pp. 783-784. | Read more

Newton P, White N. 1999. Malaria: new developments in treatment and prevention. Annu Rev Med, 50 (1), pp. 179-192. Read abstract | Read more

Malaria still kills some 0.5-2.5 million people per year in the tropics. Resistance to the cheap, most commonly used antimalarials continues to spread alarmingly and could outpace drug development. The artemisinin derivatives have had an important clinical impact both on the treatment of resistant falciparum malaria and on the incidence of disease in low-transmission areas. A few promising new antimalarials are being tested clinically but there is an imperative need for cheap, well-tolerated drugs that can be used in short courses, and for strategies to delay the onset of drug resistance. Bed nets have been shown to reduce the incidence of severe malaria in many areas but an effective vaccine is urgently needed. Hide abstract

Lalvani A, Newton P, Conlon CP. 1997. Salmonella enteritidis and acute renal failure: Report of five cases and review INFECTIOUS DISEASES IN CLINICAL PRACTICE, 6 (3), pp. 193-195.

Newton P. 1996. For creationists, a call to the bar Lancet, 347 (9002), pp. 702.

Newton P. 1996. Hypothyroid nails and evolution. Lancet, 347 (9018), pp. 1832-1833. | Read more

Newton P, Lalvani A, Conlon CP. 1996. Psittacosis associated with bilateral 4th cranial nerve palsies. J Infect, 32 (1), pp. 63-65. Read abstract | Read more

We report a 55-year-old man who presented with a moderately severe community acquired pneumonia due to Chlamydia psittaci, probably acquired from budgerigars. One of his presenting symptoms was diplopia, secondary to bilateral 4th cranial nerve palsies, which persisted for some months. The literature on neurological complications of pneumonia is reviewed. Hide abstract

NEWTON P. 1994. SOCIAL STABILITY AND CHANGE AMONG FOREST HANUMAN LANGURS (PRESBYTIS-ENTELLUS) PRIMATES, 35 (4), pp. 489-498. | Read more

NEWTON P. 1992. FEEDING AND RANGING PATTERNS OF FOREST HANUMAN LANGURS (PRESBYTIS-ENTELLUS) INTERNATIONAL JOURNAL OF PRIMATOLOGY, 13 (3), pp. 245-285. | Read more

Newton P, Wolfe N. 1992. Can animals teach us medicine? BMJ, 305 (6868), pp. 1517-1518. | Read more

Newton P. 1991. The use of medicinal plants by primates: A missing link? Trends Ecol Evol, 6 (9), pp. 297-299. Read abstract | Read more

There is growing evidence that some species of wild nonhuman primate, especially chimpanzees, take herbal and clay medicines to treat and prevent disease. Such a primate pharmacopoeia may be a missing link in our understanding of the relationship between primate foraging and ranging strategies and plant chemistry; not all plant secondary compounds may be deleterious to the consumer. Just as study of traditional herbal medicines has yielded powerful drugs, so primate medicines may hint at drugs useful in treating human disease. Hide abstract

NEWTON P, NISHIDA T. 1990. POSSIBLE BUCCAL ADMINISTRATION OF HERBAL DRUGS BY WILD CHIMPANZEES, PAN-TROGLODYTES ANIMAL BEHAVIOUR, 39 (4), pp. 798-801. | Read more

NEWTON P, RANDS M, BOWDEN C. 1990. A COLLECTION OF SMALL MAMMALS FROM EASTERN NEPAL MAMMALIA, 54 (2), pp. 239-244. Read abstract

Noted 11 species of Muridae and Soricidae. In the lowland terai sal forest and grasslands a rodent (Diomys crumpi) previously unknown in Nepal, and a rare shrew (Crocidura attenuata) were caught out of their usual altitudinal and habitat range. Millardia meltada and Mus booduga appeared to be confined to the terai. Mus musculus, Soriculus nigrescens, Rattus fulvescens and R. niviventer were only found in the hills. -from Authors Hide abstract

NEWTON P. 1990. FETAL ARM PROLAPSE AND PRESUMED MATERNAL DEATH IN A WILD HANUMAN LANGUR (PRESBYTIS-ENTELLUS) PRIMATES, 31 (1), pp. 143-145. | Read more

NEWTON P. 1989. ASSOCIATIONS BETWEEN LANGUR MONKEYS (PRESBYTIS-ENTELLUS) AND CHITAL DEER (AXIS-AXIS) - CHANCE ENCOUNTERS OR A MUTUALISM ETHOLOGY, 83 (2), pp. 89-120. | Read more

NEWTON P. 1988. THE STRUCTURE AND PHENOLOGY OF A MOIST DECIDUOUS FOREST IN THE CENTRAL INDIAN HIGHLANDS VEGETATIO, 75 (1-2), pp. 3-16. | Read more

NEWTON P. 1988. THE VARIABLE SOCIAL-ORGANIZATION OF HANUMAN LANGURS (PRESBYTIS-ENTELLUS), INFANTICIDE, AND THE MONOPOLIZATION OF FEMALES INTERNATIONAL JOURNAL OF PRIMATOLOGY, 9 (1), pp. 59-77. | Read more

Newton PN, Coe MJ. 1988. Dung and dung beetles in Kanha Tiger Reserve, central Indian highlands Journal of Bombay Natural History Society, 85 (1), pp. 218-220.

NEWTON P. 1987. THE SOCIAL-ORGANIZATION OF FOREST HANUMAN LANGURS (PRESBYTIS-ENTELLUS) INTERNATIONAL JOURNAL OF PRIMATOLOGY, 8 (3), pp. 199-232. | Read more

NEWTON P. 1986. INFANTICIDE IN AN UNDISTURBED FOREST POPULATION OF HANUMAN LANGURS, PRESBYTIS-ENTELLUS ANIMAL BEHAVIOUR, 34 (3), pp. 785-789. | Read more

Newton PN. 1986. Leapfrogging in cattle egrets (Bubulcus ibis). Journal of Bombay Natural History Society, 83 pp. 432.

Newton PN. 1986. Use of self-tindering Cordia firesaws by the Baiga of the Maikal Hills. Journal of Bombay Natural History Society, 83 pp. 475-476.

Newton PN, Breeden S, Norman GJ. 1986. The birds of Kanha Tiger Reserve, Madhya Pradesh, India Journal of Bombay Natural History Society, 83 pp. 477-498.

Newton PN. 1985. A note on golden jackals (Canis aureus) and their relationship with langurs (Presbytis entellus) in Kanha Tiger Reserve Journal of Bombay Natural History Society, 82 pp. 633-636.

NEWTON P. 1984. INFANTICIDE AND SOCIAL-CHANGE IN FOREST GREY LANGURS, PRESBYTIS-ENTELLUS, IN KANHA TIGER RESERVE, INDIA INTERNATIONAL JOURNAL OF PRIMATOLOGY, 5 (4), pp. 366-366.

Newton PN. 1984. A feeding association between a heteropteran bug and langurs. Journal of Bombay Natural History Society, 81 pp. 180-181.

RIDLEY M, NEWTON P. 1983. BIOLOGY UNDER THE RAJ NEW SCIENTIST, 99 (1376), pp. 857-&.

Ingles JM, Newton PN, Rands MRW, Bowden CGR. 1980. The first record of a rare murine rodent Diomys and further records of three shew species from Nepal Bulletin of British Museum (Natural History), 39 pp. 205-211.

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