QUESTION

I had malaria as child, more than 30 years ago. It was successfully treated with no relapse. I have since travelled to malaria- endemic countries, but the last time was over 3 years ago. No symptoms. I recently donated blood and routine screening has detected malaria antibodies. How long do the antibodies persist?

ANSWER

Based on your experience, I would say at least three years! While I doubt your antibodies would persist since your infection as a child, it is more likely that in your more recent trips to malarial areas you have been re-exposed to the parasite, but for whatever reason, the infection didn’t progress into a full-blown episode of malaria. This could well be due to some residual immunity from childhood, or you just received a light enough infection that your general immune system was able to fight off. Either way, this would have produced new antibodies against malaria, which were picked up by the blood screen.

The length of time antibodies persist is important information in the control of malaria, since serological tests (which detect antibodies) can be used for screening of populations in low-transmission environments, but their efficacy is reduced in locations where people have been treated for malaria but their antibodies persist. Also, understanding how antibodies are created and maintained in the body is necessary for gaining an appreciation of how preventive measures, such as bednets, might potentially leave populations more vulnerable to malaria later on, through lack of acquired immunity.