Distribution of Arboviruses and Mosquitoes in Northwestern Yunnan Province, China

From July to September in 2005 and 2006, a survey was conducted to identify mosquito species and mosquitoborne arboviruses at elevations ranging from 900-3280 m between 24 degrees 00' N and 29 degrees 00' N latitude in the northwestern part of Yunnan Province, China. A total of 54,879 mosquitoes representing 15 species and 4 genera was collected using UV light traps at 59 sites. Culex tritaeniorhynchus and Anopheles sinensis were the most abundant species. The density of mosquitoes as well as the diversity of species decreased with increasing altitude. A total of 21,008 mosquitoes in 281 pools representing all of the 15 species was tested for the presence of viruses using cell culture. Viruses identified included Japanese encephalitis virus (13 isolates), Getah virus (five isolates), Banna virus (three isolates), Kadipiro virus (five isolates), and Densovirus ( seven isolates). These isolates were obtained from Culex tritaeniorhynchus (20 isolates), Anopheles sinensis (three isolates), Armigeres subalbatus (six isolates), Culex pipiens quinquefasciatus (two isolates), and from unidentified, mixed mosquitoes (two isolates). Most of the isolates were from collections made at elevations below 2,500 m.