Transmission of Japanese encephalitis virus to susceptible pigs by mosquitoes of Culex tritaeniorhynchus after experimental hibernation.

Adult female mosquitoes of Culex tritaeniorhynchus were infected with Japanese encephalitis virus in the end of October, 1964. They were exposed to the winter conditions at three different places. Although their mortality was very high from the middle of November 1964 till the middle of February 1965, a small number of them could survive over the winter till at least March 24th in 1965. Japanese encephalitis virus persisted in the overwintering infected mosquitoes of Culex tritaeniorhynchus so long as they were alive. The transmission tests of Japanese encephalitis virus to susceptible pigs were carried out by confirming the presence of the virus in the mosquitoes of Culex tritaeniorhynchus which had overwintered after infection. The experimental results show that the level of infectivity in the blood of the pigs infected with such mosquiotes was enough to infect other mosquitoes. The present study suggests the possibility of overwintering of Japanese encephalitis virus in the mosquitoes of Culex tritaeniorhynchus in nature, and confirms the signifi- cance of the pig as an amplifier for Japanese encephalitis virus.