Low Prevalence of Leptospira Carriage in Rodents in Leptospirosis-Endemic Northeastern Thailand.
Krairojananan P., Thaipadungpanit J., Leepitakrat S., Monkanna T., Wanja EW., Schuster AL., Costa F., Poole-Smith BK., McCardle PW.
Leptospirosis is a neglected zoonotic disease affecting mostly the world's tropical regions. The rural people of northeastern Thailand suffer from a large number of leptospirosis infections, and their abundant rice fields are optimal rodent habitats. To evaluate the contribution of diversity and carriage rate of pathogenic <i>Leptospira</i> in rodent reservoirs to leptospirosis incidence, we surveyed rodents, between 2011 and 2012, in four provinces in northeastern Thailand with the highest incidence rates of human leptospirosis cases. We used <i>lipL32</i> real-time PCR to detect pathogenic <i>Leptospira</i> in rodent kidneys, partial 16S rRNA gene sequencing to classify the infecting <i>Leptospira</i> species, and whole 16S rDNA sequencing to classify species of isolated <i>Leptospira</i>. Overall prevalence of <i>Leptospira</i> infection was 3.6% (18/495). Among infected rodents, <i>Bandicota</i><i>indica</i> (14.3%), <i>Rattus</i><i>exulans</i> (3.6%), and <i>R</i>. <i>rattus</i> (3.2%) had renal carriage. We identified two pathogenic <i>Leptospira</i> species: <i>L</i>. <i>interrogans</i> (<i>n</i> = 15) and <i>L</i>. <i>borgpetersenii</i> (<i>n</i> = 3). In addition, an <i>L</i>. <i>wolffii</i> (LS0914U) isolate was recovered from the urine of <i>B</i>. <i>indica</i>. <i>Leptospira</i> infection was more prevalent in low density rodent populations, such as <i>B</i>. <i>indica</i>. In contrast, there was a lower prevalence of <i>Leptospira</i> infection in high density rodent populations of <i>R</i>. <i>exulans</i> and <i>R</i>. <i>rattus</i>.