蚊の分類と生態及び熊本県での蚊の日本脳炎ウイルス調査

Abstract

The mosquito transmits various illness to the human. The major transmitter mosquito is the genus Anopheles, the genus Culex and the genus Aedes. There are some differences in the site of larva’s occurrence, the blood-sucking behavioral pattern, the blood-sucking preference and the winter style, between genera. It is important for Disease Control and Prevention to understand taxonomy and ecology of mosquitoes.To investigate the rate of mosquitoes keeping Japanese encephalitis virus, we collected mosquitoes at pig farms by CO2 net traps in Kumamoto from 2012 to 2013. Approximately 20,000 out of about 23,000 captured mosquitoes have been identified as Culex tritaeniorhynchus (Ct). Twenty eight out of 520 pooled mosquito were Japanese encephalitis virus (JEV) gene positive by PCR assay. Genotype I of JEV was isolated from the 2 pooled samples. At the result of phylogenetic tree analysis of isolates, the strain that was isolated from mosquitoes in 2012 was correlated with the cluster that have been isolated from mosquitoes at Korea in 2010. The homology of these strains was 99% at envelop (E) gene region. In addition, the E region of the strain from mosquitoes in Korea in 2010 completely corresponded to that of the isolates from pigs at Kumamoto in 2009 and 2010. Additionally, to investigate whether the Ct has come from the continent, eight Ct were collected by net traps for planthoppers. Two Ct were determined to be the continent genotype by analysis of the mosquito mitochondrial DNA (COI), but JEV gene was not detected from these Ct. Results of the phylogenetic tree analysis of these JEV isolates and the analysis of COI, suggested the possibility that the Ct keeping JEV has come from the continent.