Student elective for Rosalie Douglas. (360G-Wellcome-080932_Z_06_Z)

Knowlesi malaria infections among humans in the Kapit Division of Sarawak, Malaysian Borneo. Malaria in humans is commonly caused by 4 species of Plasmodium: P. falciparum, P. vivax, P. malariae and P. ovale. It was recently reported that more than half of 208 hospital admissions for malaria in the Kapit Divison of Malaysian Borneo that were studied were due to P. knowlesi (Singh et al., 2004), a malaria parasite of long-tailed and pig-tailed macaque monkeys. Due to the morphological similarities between P. knowlesi and P. malariae, these infections were misdiagnosed by microscopy mainly as P. malariae. Correct identification required the use of newly developed P. knowlesi -specific primers in a nested PCR malaria detection assay. This assay can detect between 1-6 parasites per µ1 blood and is more specific and sensitive than microscopy, which has a limit of detection of approximately 100 parasites per µ1 blood. The Kapit Division of Sarawak is the largest of the administrative divisions with an area of 38,934 m2 and a population of 101,120. The people of the divisions are served by one district hospital at Kapit Town and 22 health clinics. People that are found to be positive for malaria by microscopy at the Kapit Polyclinic are admitted into Kapit Hospital. Those that are negative by microscopy for malaria are usually not admitted into hospital unless their medical condition is serious. It is not known whether a number of patients with malaria, particularly knowlesi malaria, are not diagnosed with malaria by microscopy due to low parasite counts and return to their communities and are potential source of human infections. Preliminary data has indicated that monkeys in Kapit are infected with P. knowlesi but it is not clear whether monkeys are the source of the infections or whether the parasite has switched hosts and transmission is human-to-human. Clustering of knowlesi malaria cases within longhouse communities, particularly among children, would suggest that human-to-human transmission is occurring. In order to examine whether clustering of knowlesi malaria cases occurs, it is essential that all malaria infections be detected. The main aims of the project are to accurately determine the number of outpatients at Kapit Polyclinic that are infected with malaria parasites, determine the sensitivity of detection of malaria by microscopy at Kapit Polyclinic and determine whether clustering of cases occur within longhouse communities.