Distribution of Mosquitoes and Mosquito-Borne Viruses along the China-Myanmar Border in Yunnan Province

A total of 54,673 mosquitoes were collected at 11 sites located near the China-Myanmar border in the western part of Yunnan Province during July and August 2007. There were 29 species in 4 genera identified from the collections, including 12 species of Culex, 12 species of Anopheles, 3 species of Aedes, and 2 species of Armigeres. Culex tritaeniorhynchus Giles (67.9%, 37,119/54,673) and Anopheles sinensis Wiedemann (25.9%, 14,170/54,673) were the most abundant species in this investigation. Virus was isolated using BHK-21 and C6/36 cells from 22 of 510 mosquito pools. Isolates included Japanese encephalitis virus (JEV) and Getah virus (GETV), which were identified by serological and molecular methods. Twenty JEV strains were isolated from Cx. tritaeniorhynchus (15 isolates), An. sinensis (3 isolates), and Armigeres subalbatus Coquillett (2 isolates), and 2 GETV strains were isolated from Culex pseudovishnui Colless and Cx. tritaeniorhynchus. This study suggests that Ar. subalbatus is a potentially important local vector because of the high JEV infection ratio found in this species. Enzootic JEV transmission persists in this area and therefore, surveillance for human disease caused by JEV and GETV should be conducted in the region.