Seasonal Abundance of Larval Stage of Culex Species Mosquitoes (Diptera: Culicidae) in an Endemic Area of Japanese Encephalitis in Mysore, India

Seasonal abundance of larval stage of Culex species including Culex vishnui subgroup, the major vectors of JE virus, was studied in Mysore and Mandya, Karnataka state, India during 2002-2004. The larvae of Culex sp. have been collected from temporary and semi permanent ground water pools. Simultaneously they have also been collected from plain rice field area from Mandya district an endemic area of Japanese encephalitis. Culex species including Culex bitaeniorhynchus, Cx. nigropunctatus, Cx. barraudi and Cx. hutchinsoni were seen only in paddy field habitat, whereas Cx. quinquefasciatus and Cx. gelidus were found only in ground pool habitats. Culex tritaeniorhynchus, Cx. vishnui, Cx. pseudovishnui, Cx. fuscocephala, Cx. murreli and Cx. fuscanus were recorded from both the breeding places. Cx. tritaeniorhynchus from Mysore city in ground pools breeds throughout the year except February and April, with a maximum density of 50.00 larvae per dip in May and the lowest being 0.25 larva per dip in September (2002-04). However Culex tritaeniorhynchus from Mandya district in paddy field was found to breed throughout the year, with the maximum density of 11.50 larvae per dip in March and the minimum being 0.06 per dip in October (2002-04). Two peaks of larval density of Cx. tritaeniorhynchus was observed in October and May in Mysore city during 2002-04 which coincides with the JE transmission season in Karnataka state. The seasonal abundance of Culex sp. from two habitats especially vectors of Japanese encephalitis are discussed.