Malaria in the Thai national parks

I work with a Thailand-based malaria research team that undertakes a research and offers diagnostic and treatment services for malaria.

Whilst I am not a doctor, I can tell you what I have learned about malaria in Thailand through my work. There are two species of malaria that make up the vast majority of malaria infections in humans in Thailand, these are Plasmodium vivax (that is the species of malaria that can give you repeated bouts of illness, but is very rarely fatal) and P. falciparum (much more dangerous to the patient, potentially being severe and fatal). The overall national caseload has been falling for the past decade, but the emergence of falciparum parasites that exhibit tolerence/resistance to the first line medicines presents a real threat to malaria control globally. This threat has understandably spooked the medical community and there are now huge efforts taking place across the Greater Mekong sub-region to control and eliminate falciparum malaria. These efforts are starting to bare fruit and we can see the number of falciparium cases is dropping, however these efforts must be sustained to ensure that falciparim does to re-emerge.

The majority of cases of malaria diagnosed in Thailand are found in migrant workers and their families coming from Myanmar (mostly) and Cambodia. Most cases are in working aged males (ie those spending time in forest or forest edge environments for employment).

In terms of malaria in national parks in Thailand, I am personally aware of two cases of people getting malaria - one involved a couple I know who slept in forest in one of the parks (I am not sure which one) on the Thai-Myanmar border in 2006 and both ended up getting falciparum malaria. The other involved birders visiting Kaeng Krachan NP in the late 1990s or early 2000s contracting malaria (I am not sure if this was vivax of falciparum).

Personally I spend a reasonable amount of time birding in forest in Thailand and I have never considered taking prophylaxis. Our Unit has a team that spends significant periods of time working cross-border in remote forested areas of the Thailand/Myanmar border and they do not take prophylaxis. This is because the Thai-Myanmar border is in a zone of "low transmission" where even if you were to spend every night in the forest you might only expect to get something like 0.5 or 1 malarial bites per year (this compares with parts of sub-saharan Africa where you can expect 365+ malarial bites per year (ie one per day).

Most importantly, the strategy that we encourage is that if you suspect you might have malaria (ie you get a fever a few days after being in the forest) you should get tested as soon as possible, ideally within 24 hours from the onset of fever (a rapid stick test can give you a result in about 20 minutes).

Personally, as a Bangkok resident I am more concerned by Dengue Fever.

Best wishes,

N

Sorry onflipflops, I should have stated that the majority of migrant workers diagnosed with malaria have a recent history of travel in Myanmar, and for the most part this is where it is being contracted. Vectors and transmission have been much less effectively controlled inside Myanmar, though the interventions to stop drug resistance spreading are now rectifying that is some border areas.

The number of cases of symptomatic malaria diagnosed in Thailand in people with no recent history of travel to neighbouring countries is apparently very small.