Aedes triseriatus and La Crosse virus: similar venereal infection rates in females given the first bloodmeal immediately before mating or several days after mating.

Abstract

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 offsetting the erosion of virus prevalence during TO transmission.