Use of Malaria Rapid Diagnostic Test to Identify Plasmodium knowlesi Infection

Reports of human infection with Plasmodium knowlesi, a monkey malaria, suggest that it and other nonhuman malaria species may be an emerging health problem.We report the use of a rapid test to supplement microscopic analysis in distinguishing the 5 malaria species that infect humans. R ecent reports of Plasmodium knowlesi infections inhumans in Sarawak and Sabah in Borneo and in the Pahang Peninsula of Malaysia have focused attention on the potential of monkey malarias to be a human health issue (1,2).As much as 70% of malaria infections in regional hospitals in Borneo are the result of P. knowlesi infection; similar infections have been found in Thailand, the Philippines, and Singapore (3-5).To date, only patients in hospitals are being screened for the disease.To better understand the epidemiology of this apparent outbreak of P. knowlesi in humans, one needs a method to rapidly screen both monkeys and humans in areas of high disease prevalence, regardless of their present health status.Thus, a rapid test that could detect and distinguish among the primate malarias would not only benefi t individual patients but would also provide an important epidemiologic tool to monitor the overall risk and prevalence of malaria.We have known for nearly 8 decades that, under laboratory conditions, several monkey malarias are capable of infecting humans and that P. knowlesi can be transmitted to humans by mosquito bite (6,7).Work in Malaysia by a team from the National Institutes of Health nearly 50 years ago reported that transmission to humans was not occurring to any prevalent extent.Currently, we see major foci of the disease, which can be life-threatening.Although the current overall incidence of P. knowlesi infection in humans is low, an exacerbating problem is that it can be consistently misdiagnosed by microscopy