Aedes triseriatus and La Crosse Virus: Similar Venereal Infection Rates in Females Given the First Bloodmeal Immediately before Mating or Several Days after Mating

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  • Department of Entomology, University of Wisconsin, Madison, Wisconsin 53706

Venereal infection rates of Aedes triseriatus females mated to males transovarially infected with La Crosse virus were determined in 6 cage-mating trials. In trials 1–4, venereal infection rates averaged 46% and 45% in F2 females bloodfed 6–8 hr before and 7 days after exposure, respectively, to transovarially-infected males. These rates were similar to rates previously reported only in mosquitoes receiving a bloodmeal 6–8 days prior to mating. Lower rates (24%–31%) were obtained using F4 and F7 generation mosquitoes in trials 5B and 6. In most trials, oral and transovarial transmission rates by venereally infected females were less than 25%. In trial 5B, however, the transovarial transmission rates reached 60% and 94% in the second and third ovarian cycles, respectively, with filial infection rates of 46% and 65%, respectively. The oral transmission rate in this trial reached 38% after 32 days. LAC virus was not detected in first ovarian cycle progeny. It is concluded that higher venereal infection rates must be found and/or first ovarian cycle progeny shown to become infected, before venereal transmission can be considered to make more than a modest contribution to offseting the erosion of virus prevalence during TO transmission.