There is always time a first time for everything – I made my first ProMED post a couple of days ago. A fellow ID physician in private practice and I recently encountered two persons who were diagnosed with malaria and who had both returned from a camping trip in Brunei.

Screenshot of ProMED post.

Their infections were not caused by any of the known human malaria species however, but by the simian malaria parasite Plasmodium knowlesi. The definitive review article on this very interesting cause of zoonotic malaria is available here. It was fascinating to learn that P. knowlesi was also initially used as malariotherapy for the treatment of neurosyphilis in the years before penicillin was discovered (P. vivax was more commonly used, and is well known for this historical purpose), but its use was discontinued when researchers found that the parasite became more pathogenic after multiple passages in humans with neurosyphilis.

It is certainly known to be a cause of severe malaria today. More recently, researchers from Charles Darwin University (Australia) and Sabah (Malaysia) showed that the use of artesunate and mefloquine in combination was superior to chloroquine monotherapy. One of the senior researchers for this study is a unique Singaporean infectious diseases physician who is currently with the Lee Kong Chian School of Medicine.

Digressions about monkey malaria aside, there are certain implications and questions raised as a result of these cases that have almost certainly contracted P. knowlesi from their trip to Brunei (“almost certainly” because Singapore is also known to have P. knowlesi circulating among local macaque monkeys, with very rare instances of zoonotic malaria). I will hopefully be able to address this another time, soon.