Geographic information system (GIS) mapping of lymphatic filariasis endemic areas of Gampaha District, Sri Lanka based on epidemiological and entomological screening

Abstract

The objective of this study was to develop a site directed geographic information system (GIS) map of lymphatic filariasis (LF) in Gampaha District, Sri Lanka as a guide for targeted control activities. Epidemiological and entomological screening of LF was carried out in nine pre-identified endemic areas in Gampaha District, using night blood screening and pool-screening PCR-ELISA. In total, 1,073 subjects (286 children, 787 adults) from 9 sites were examined. Positive cases were detected at 2 sites, with prevalence rates of 0.5% (Hekiththa) and 3.4% (Peliyagoda); the prevalence of microfilaria (mf) among adult Culex quinquefasciatus mosquitoes surveyed was 30%. The overall prevalence of mosquitoes with L1-L2 larvae of W. bancrofti ranged from 0% to 8.31% using dissection and point estimates of infection prevalence, and ranged from 0 to 32.4% using PCR-ELISA. The largest number of human cases was found at altitudes of 2.5-3.5 min highly populated areas, where transmission appears to have taken place. Questionnaires indicated that limited community awareness of LF may be a reason for the fairly static infection prevalent among the local population. The GIS mapping of LF cases shows a considerable prevalence of LF and marked variability by geographic site in Gampaha.