VECTOR COMPETENCE OF SELECT BLACK FLY SPECIES FOR VESICULAR STOMATITIS-VIRUS (NEW-JERSEY SEROTYPE)

Black flies collected from southern Arizona were evaluated for their v ector competence to the Oaxaca and Camp Verde isolates of vesicular st omatitis virus (New Jersey serotype) (VSV-NJ). The Camp Verde isolate is the index isolate of the 1982-1983 VSV-NJ epizootic that infected h umans and livestock in 14 western states. Previous experiments have sh own that colonized Simulium vittatum females are competent laboratory vectors of both virus isolates. However, under controlled laboratory c onditions, Simulium bivittatum and S. longithallum were found to be in competent vectors of both virus isolates. After oral infections, the O axaca isolate replicated in 35% and 38% of S. bivittatum and S. longit hallum, respectively, but did not disseminate to the salivary glands. Thus, virus was not detected in the saliva of either black fly species with either VSV-NJ isolate. indicating the presence of a midgut barri er Simulium notatum was found to be a competent laboratory vector of b oth virus isolates. Infectious virions were detected in the saliva of 23% and 26% of S. notatum infected orally with the Oaxaca and Camp Ver de VSV-NJ isolates, respectively. This study suggests that the black f ly identified as S. bivittatum was probably not involved in virus diss emination during the 1982-1983 epizootic in the western United States. Because the geographic distribution of S. notatum is not known, its i nvolvement in that epizootic remains obscure.