VECTOR COMPETENCE OF COLONIZED CULISETA-MELANURA (DIPTERA, CULICIDAE) FOR WESTERN EQUINE ENCEPHALOMYELITIS VIRUS

The susceptibility of Culiseta melanura to infection with strains of Western equine encephalomyelitis virus isolated in the eastern United States was determined by intrathoracic inoculation, by feeding on blood-virus mixtures through a membrane, and by feeding on viremic chicks. To infect 50% of the Cs. melanura by the inoculation route, 0.05 baby mouse median lethal doses of virus were necessary. Cs. melanura was the most sensitive of 8 mosquito species compared by this technique. By membrane feeding and by feeding on viremic chicks, ca 3.7 logs and ca 1.5 logs, respectively, of virus were necessary to initiate infection in 50% of the Cs. melanura. This species was capable of transmitting virus as early as 6 days following an infectious blood meal, and of the infected females held for 14 or more days at 27°C that refed on chicks, 86% successfully transmitted virus. The kinetics of virus replication in Cs. melanura following inoculation was studied at 18° and 27°C.