Outdoor resting preference of Culex tritaeniorhynchus, the vector of Japanese encephalitis in Warangal and Karim Nagar districts, Andhra Pradesh

Background & objectives : Entomological investigations were carried out in Warangal and KarimNagar districts of Andhra Pradesh during viral encephalitis outbreak in July 2003.Methods : Adult mosquito collections in outdoor were done using sweep cage method and in indoorwith the help of aspirator tube and flash light. Larval collections were done by dipping method. JEvirus positivity was tested by IgM capture ELISA test.Results : Outdoor collections revealed presence of Culex tritaeniorhynchus, Cx. bitaeniorhynchusand Cx. gelidus and in indoor collections —Cx. quinquefasciatus, Cx. tritaeniorhynchus, An. vagusand An. subpictus. In the outdoor collections Cx. tritaeniorhynchus was predominant (96.3% of totalcollection). Three samples out of 55 serum samples from human cases and five from contacts showedthe presence of antibodies against JE virus.Interpretation & conclusion : Cx. tritaeniorhynchus, a known vector of JE is predominant in outdoorsand playing a main role in JE transmission in this area. Vector control aimed at the outdoor restingpopulation might limit virus circulation in the mosquito vertebrate host cycle and prevent humaninfection