Profile of Morong, Bataan, an area of low malaria endemicity in the Philippines

A malaria study area in the Philippines is described. It consists of the municipality of Morong, Bataan on the Island of Luzon. In January 1992, the population was 19 454 in 106 villages located on a narrow coastal plain, or in valleys of streams running from the mountainous interior. This is an area of low level but persistent seasonal transmission of malaria with approximately one thousand cases reported each year, mainly from February to July. In spite of the low level of malaria, it is apparently quite stable. The study site has been used to investigate parameters leading to stable malaria. Hypotheses tested were that there was substantial under reporting of cases; that there was strain specific immunity stabilising the incidence of malaria and that malaria transmission in this area is highly localised in small regions with a high enough malaria prevalence to account for the year to year stability. The study plan included cross sectional surveys of parasite prevalence and seropositivity, longitudinal surveys, passive case detection, entomological surveys, anthropological surveys to assess knowledge of malaria and documentation of the health-seeking behaviour of the population.