BIOLOGICAL TRANSMISSION OF VESICULAR STOMATITIS-VIRUS (NEW-JERSEY) BY SIMULIUM-VITTATUM (DIPTERA, SIMULIIDAE)

Simulium vittatum females were shown to be competent vectors for the New Jersey serotype (VSNJ) of vesicular stomatitis virus (Camp Verde strain). Seventy percent of females infected intrathoracically transmitted infectious virions in their saliva after a 10-d incubation period. When infected with virus per os, 63% of the flies tested were positive at day 10, and 45% of flies infected in this manner also secreted virus in their saliva by day 9 or 10 after infection. When ingested by S. vittatum females, VSNJ virus readily replicated and increased from a mean baseline titer of 1.2 x 10(4) pfu per fly to 3 x 10(4) pfu per fly on day 10. An eclipse phase was demonstrated between almost-equal-to 18 and 48 h postinfection. This experimental evidence supports the hypothesis that black flies play a major role in the epizootic transmission of VSNJ. This is also the first confirmed example of biological transmission of an arbovirus by a member of the Simuliidae.