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.
Present address: 3rd Medical Division, Bellevue Hospital, 27th Street and First Avenue, New York City 16, N. Y.
Present address: Dept. of Bacteriology and Immunology, University of Minnesota Medical School, Minneapolis 14, Minnesota.
Present address: U.S. Naval Medical Research Unit No. 2, APO 63, San Francisco, California.
Present address: Dept. of Bacteriology and Immunology, School of Medicine, University of Minnesota, Minneapolis 14, Minnesota.