Studies on the susceptibility of mosquitoes to dengue virus : I. Susceptibility of Japanese mosquitoes to the virus

Abstract

Females of 15 species of Japanese mosquitoes were studied to determine if they were susceptible to mouse-adapted dengue-2 virus (New Guinea C strain) by oral administration of the virus mixed with rabbit blood and sucrose. The following species were tested : Aedes (Stegomyia) albopictus, Ae. (Stg.) flavopictus, Ae. (Stg.) riversi, Ae. (Ochlerotatus) dorsalis, Ae. (Aedimorphus) vexans nipponii, Ae. (Finlaya) japonicus, Ae. (Fin.) togoi, Armigeres (Armigeres) subalbatus, Anopheles (Anopheles) sinensis, Culex (Culex) orientalis, Cx. (Cux.) pipiens molestus, Cx. (Cux.) pipiens pallens, Cx. (Cux.) pipiens quinquefasciatus, Cx. (Cux.) tritaeniorhynchus and Tripteroides (Tripteroides) bambusa. Several hundred mosquitoes were used for each species. They were kept at 30℃ after the infection, and were stored at -80℃ after the incubation of various time length from 0 to 30 days. The detection and titration of the virus were made by the intracranial injection of a suspension pool of 10 mosquitoes in suckling mice (ddY strain). The virus was detected at varying titers from all the mosquito species immediately after the infection, but was detected after 20 days of infection only from the four species, i. e., Ae. (Stg.) albopictus, Ae. (Stg.) flavopictus, Ae. (Stg.) riversi and Ae. (Och.) dorsalis, ranging from "trace" to≧(10)^<4.6> LD_<50> per pool. In more detailed studies with the positive mosquito species, the virus was found to multiply after an eclipse period of 7 to 10 days and to reach a peak titer after 20 to 30 days.