[The natural infection rate of mosquitoes by Japanese encephalitis B virus in Yunnan Province].

In July-September 1983-1987, 57,898 adult female mosquitoes belonging to 29 species of 8 genera were collected from Japanese B encephalitis (JE) epidemic areas in Yunnan, China, and were examined by C 6/36 cell method and sucking mouse method. Twenty-eight strains of JE virus were isolated from Culex tritaeniorhychus, C. whitomorei, C. pseudovishnui, C. fuscocephala, C. annulus, C. gelidus, Anopheles sinensis, Mansonia uniformis, Aedes albopictus, Ae. Vexans, Ae. lineatopennis, and Ae. assamensis. The positive isolation rates by the two methods were 6.19% and 3.33% respectively. The highest positive isolation rate 12.3% (per 100 pools), moiquito body virus carrier rate 1:208 or moiquito body virus carrier rate 4.81% (per 1000 mosquitoes) were found in the middle ten days of August, corresponding to epidemic peak of JBE Nine strains of JE virus were isolated from C tritaeniorhychus with an isolation rate of 7.44%, natural isolation ratio was 1.584 and mosquito body virus carrier rate 1.71%. These results indicated that C. tritaeniorhynchus might be the main vector of JE virus in Yunnan, while C. whitmorei, C. pseudovishnui and An. sinensis are also important vectors of JE virus in Yunnan.