Patterns of monthly Culex mosquito density variation in Gampaha district, Sri Lanka.

Abstract

BACKGROUND: The ecology, development, behavior, and survival of mosquitoes and the transmission dynamics of the diseases they transmit are strongly influenced by climatic factors. OBJECTIVE: The objective of this study was to identify the population density variation of Culex mosquitoes within a period of one year in Gampaha district, Sri Lanka together with potential climatic factors that influenced the Culex population density variation. METHODOLOGY: Culex mosquitoes were routinely collected on monthly basis from 9 sites in Gampaha district. Climate data was obtained from the Department of Meteorology. RESULTS: An exponential growth of Culex population densities was observed in all sites starting in December to February during the study period. The maximum density occurred in January and decreased from March until July. It again increased during August and thereafter decreased until December. Among the study sites the maximum Culex density (mosquitoes/man-hour) was observed in Hekiththa ranging between 89 to 22 and the minimum was from Kurukulawa ranging from 6 to 1. Climatic data suggest that temperature is a limiting factor for the Culex population growth while it was strongly influenced by the rain fall pattern. DISCUSSION: Similar Culex population density variation pattern was observed in all sites but exhibited enormous variation between sites, probably due to different local conditions. Also it was suggested that estimation of W, bancrofti transmission levels in Culex mosquitoes should be practiced in field settings where high mosquito density was observed. Since mosquito density appears difficult to be analyzed by individual dissection use of pool-screen PCR-ELISA would be a better method.