Studies on the mosquito vectors of Japanese encephalitis virus in Mandya District, Karnataka, India.

Entomological investigations were carried out in areas affected by Japanese encephalitis (JE) in Mandya District, Karnataka, India, from 1983 to 1988, to determine species composition and the density of mosquito vectors, in relation to the incidence of JE cases. JE cases occurred in two spells in a year, one during April-June (summer epidemic) and another during October-December (winter epidemic). There was very high incidence of JE cases in extensively irrigated areas and a low incidence in some of the taluks with less or no irrigation systems. Among culicines, Culex tritaeniorhynchus was the most predominant species (20.54%), followed by Cx. fuscocephala (16.94), Cx. vishnui (16.48%), Cx. gelidus (10.70%) and other species. The overall mosquito population showed two peaks in a year, one during the March-April, and another during September, usually preceding the human epidemics. Relative abundance of certain species varied in different years.