Factors Influencing Transmission of Japanese B Encephalitis Virus by a Colonized Strain of Culex Tritaeniorhynchus Giles, from Infected Pigs and Chicks to Susceptible Pigs and Birds

Abstract

Summary C. tritaeniorhynchus, the principal mosquito infected in nature by Japanese encephalitis virus in Japan, was shown, after colonization and propagation for 12 to 17 generations in the laboratory, to transmit JE virus readily from chick to chick and from pig to pig, to Blackcrowned Night Heron, to egrets and to baby chicks. Mosquito infection and transmissions followed ingestion of blood containing as little as three mouse-LD50 of JE virus/0.04 ml blood (0.15 LD50/mosquito). The concentration of virus in blood of the host chick or pig governed the numbers of mosquitoes infected and, consequently, the overall transmission rate, although some infected mosquitoes failed to transmit virus. Virus was recovered from mosquitoes within several days after feeding on a viremic animal, but transmission usually did not occur until more than 2 weeks (range of 9 to 34 days) after ingestion of viremic blood.