Vector Competence of Aedes Hendersoni (Diptera: Culicidae) for La Crosse Virus and Evidence of a Salivary-Gland Escape Barrier1

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Abstract
Seven strains of Aedes hendersoni were infected orally with La Crosse virus. Subsequent refeeding on suckling mice showed, contrary to an earlier report, that all strains were able to orally transmit at low levels. The mean transmission rate (9%) was significantly less than for Aedes triseriatus (62% for the WALTON control strain); however, the dissemination rate for Ae. hendersoni was significantly higher (85% vs. 68% for Ae. triseriatus). In some individual Ae. triseriatus, a mesenteronal escape barrier blocks virus dissemination. This barrier is virtually absent in Ae. hendersoni. The significantly lower transmission rate by Ae. hendersoni is apparently due to a salivary-gland escape barrier. Salivary glands of both species were dissected 21 days after an infectious blood meal. Infectious La Crosse virus was isolated in cell culture from Ae. hendersoni (11 of 17 glands) as well as Ae. triseriatus (10 of 17 glands). Indirect immunofluorescence indicated that 8 of 8 glands from Ae. hendersoni had viral antigen within the tissue.