A study of determinants of malaria in Kelantan, Malaysia

Abstract

The candidate conducted operational research, in collaboration with the Vector-Borne Diseases Control Program (VBDCP), Kelantan, Malaysia, to analyze determinants of malaria incidence at different geographic scales: the state (inter-annual and intra-annual rainfall, and other seasonal events); the district (age- and sex-specific risk groups in relation to blood-film collection methods: Passive Case Detection [PCD], Active Case Detection [ACD], Investigation Surveys [INV]); and the village/individual domicile (environmental and behavioral variables). Routine operational data from the VBDCP were used as far as possible. Statewide statistics showed clear association of malaria with intra-annual rainfall variation but in a mixed correlation: high or low rainfall reduce malaria incidence, while moderate rainfall increases incidence. Inter-annual EI Nino Southern Oscillation events, which cause drought in southeast Asia, were associated with reduced malaria incidence. Rubber price and production, and fruit seasons could not be conclusively associated with incidence. All malaria blood-films examined during 1991 in Gua Musang district were entered to a database permitting age- and sex-stratified analysis of the populations sampled by PCD, ACD, and INV. Relative to the census population, the blood-film collection over-samples children and young adult males, but these risk groups still have higher incidence. PCD was most efficient in detecting malaria cases, but ACD and INV were most effective in detecting falciparum gametocytemia. A case-control study of behavioral and environmental determinants of malaria (largely taken from the routine case investigation form) in Jerek village proved inconclusive due to small sample size, resulting from low malaria transmission.