In 2007 we travelled to Kenya and Zanzibar. We took the normal anti-malarial tablets and were unaware of having been bitten. My older son has recently had a full medical and one of the blood tests which he had to repeat came back with a high count for malaria antibodies for Plasmodium falciparum. The doctor told him that he had had malaria at some time. We are puzzled as he has never been ill since returning. Can this happen? On the other hand my younger son has not been fully fit since returning from the trip, flu like symptoms, lack of energy etc. He has had several blood tests including one for glandular fever but nothing has shown up. Should he be tested for malarial antibodies? Could this be the reason he has had recurrent bouts of illness.
It is certainly possible to be exposed to malaria, but for your body to successfully fight the infection before it can reproduce and establish, thus the person will never experience the full illness. This is likely what happened with your elder son. As for your younger one, malaria tends to be an acute illness rather than a long-lasting chronic one, particularly the types of malaria that are found in East Africa.
Since your elder son was exposed and seems to have antibodies to malaria, I don’t think an antibody test will be particularly illuminating with regards to diagnosing your younger son. It would be better to have the doctors test him for malaria using the traditional thick and thin blood smears, which are then looked at under the microscope. This test will better inform the doctors whether your son has an active malaria infection, and will also be able to determine the species of malaria he has (if positive), and thus what treatment would be most effective for him. Again, though you should do this test to rule out malaria for sure, I think it is unlikely that your son has been experiencing symptoms caused by malaria for this length of time.