Question: Up to the age of 20 I lived in Malaysia Singapore and North Borneo – born 1953. Is is possible that during that time I contracted either malaria or dengue and because it was never treated it is still in my system.
Answer: While there is some evidence of long term clinical symptoms associated with dengue infection, I have not heard of a case that would have persisted across multiple decades. Even in those cases of relapse after a few years, it appears to be more likely caused by longer term effects of the infection on the immune system, rather than persistence of the virus itself.
There are some types of malaria, notably caused by Plasmodium vivax or P. ovale, which can persist for weeks, months, or even years in the body, and cause new bouts of infection. The malaria parasites hide in the liver before re-emerging into the blood stream and causing symptoms. These types of malaria are known to be found in Southeast Asia, particularly North Borneo, so it is possible that you could have been infected as a child or young adult.
There are two possible approaches for diagnosis: you could take a test that looks for antibodies against malaria, which could tell you whether you have been infected with malaria in the past. Some antibodies persist longer than others, so it might be able to tell you if you have had a relatively recent relapse.
However, it won’t tell you definitively if the parasite is still in your system. The only way to do this is to conduct a blood smear or other direct test to look for the malaria parasite while you are having a relapse – these tests will only detect parasites if they are circulating in the blood, not if they are hiding in the liver. The current treatment for long-term relapsing malaria caused by P. vivax and P. ovale is a drug called primaquine – however, it cannot be used in people with deficiency in an enzyme called glucose-6-phosphate dehydrogenase (G6PD) so you should ask your doctor about being tested for this enzyme deficiency before embarking on a course of treatment with primaquine.