David Dance: Bacterial infections in Laos
Laos is seing a growing number of melioidosis, a bacterial infection caused by a bacterium that lived in the environment. Meliolidosis is a disease greatly under-recognised and treatment is specific, making it a major threat to farmers in developing countries. A better understanding of the prevalence of this infection and how it spreads allows us to better target prevention and treatment.
This is a podcast from the Nuffield Department of Medicine. Today we speak with Professor David Dance about bacterial infections in Laos.
Q: Which bacterial infections are important issues in Laos?
David Dance: We see a lot of the same bacterial infections that you would find in the UK or elsewhere in Europe but in larger numbers. We have the usual staphs and streps and also problems like tuberculosis, which is very common, and leptospirosis. There are also things that are unique to the tropics like typhus: scrub typhus, murine typhus, typhoid. There are some things that people acquire from animals like streptococcal suis that can cause meningitis and septicaemia. But what I am particularly interested in, and we see a growing amount of in Laos, is a disease called melioidosis.
Q: Who is most at risk of melioidosis?
DD: It is particularly people who are in contact with soil and water because it is caused by a bacterium that lives in the environment; it lives in paddy fields. The people who are particularly at risk are rice farmers who are being exposed to the organism all the time, but it can infect almost anybody. You can also breathe it in and probably drink it in as well and get infected that way. If your water is contaminated and you drink it, or if you go out in a particularly heavy rainstorm then you can be infected. It is particularly likely to infect people whose immune system isn’t working properly and there is a very strong association with diabetes. If you are a diabetic rice farmer then you are at very high risk of melioidosis.
Q: How can we reduce the prevalence of melioidosis?
DD: The first thing is to understand the prevalence, and this disease is greatly under-recognised. Most people, even in countries where the disease exists, have never heard of it. Most doctors in the UK have never heard of it. We are beginning to understand, as laboratories spread in countries like Thailand, Laos and elsewhere in the tropics, that this disease is far more common than people realised. The people who are likely to get it are the people who are least likely to have access to diagnostic laboratories to make the diagnosis. Once we have realised that it exists in an area then the measures required to prevent it should be relatively straightforward: wearing boots or waders when going into a paddy field, trying to make sure that you drink only boiled or bottled water, and avoiding going outside in really heavy rain storms. It sounds easy but if you are a rice farmer in rural Laos it is quite difficult to achieve.
There are people working on developing vaccines but at this stage they are purely experimental and whether they will ever get to be used in real life remains to be seen.
Q: What are the most important lines of research that have developed in the past 5 or 10 years?
DD: In the past 5 to 10 years I think that research into the organism and understanding the bacterium has exploded, as we have the new tools of genomics and we have been able to dissect out the genetic makeup of the organism. That has taught us a lot about how it causes disease and also fascinatingly about how it has evolved. It seems to have started off in Australia and then spread to South East Asia and from there to Africa and South America. But to actually impact on the management of the disease, that has had relatively little impact so far.
The other growing area of research is where the disease exists. When I first started working on it 30 years ago, people would have said that it is a disease of South East Asia and Northern Australia. We now know that it is much more widespread than that. A particularly important paper that was published this year (2016) looked at modelling where in the world the disease occurs and how much of it there might be. The bottom line is that we think that there might be as many as 165,000 cases a year of this disease occurring worldwide and leading to as many as 89,000 deaths. That makes melioidosis a more important killer than diseases that are much better known, like dengue or leptospirosis.
Q: Why is this research so important, why should we fund it?
DD: Until we know how much of the disease there is, people are dying needlessly because it is treatable, but it is not usually susceptible to the normal treatments that are used for fevers, pneumonia, and abscesses in people in the developing world. We need to understand where it is and then we can target the appropriate treatments at people who would otherwise die because they don’t get effectively treated. I have mentioned the association with diabetes, and diabetes is becoming more and more common in the developing world and in the tropics. We expect that as diabetes spreads and as the number of diabetics increases that the number of people with melioidosis increases.
Q: How does your research fit into Translational Medicine within the Department?
DD: One of the unique things about Oxford and the Oxford Tropical Network is that we have people, like me, based at the coalface in the field, in the tropics. We are able to link in to this amazing resource within Oxford. I have talked about genomics: colleagues in Oxford are able to take the organisms that we grow from real patients, or from real paddy fields, and they can sequence the genomes and tell us a huge amount about the organism and maybe help us explain some the differences that we see between patients. Having that link between the coalface and the cutting edge research back in Oxford is a wonderful resource.
This interview was recorded in September 2016