Laboratory studies of transovarial transmission of La Crosse and other arboviruses by Aedes albopictus and Culex fatigans.

Transovarial transmission of La Crosse virus by experimentally infected Aedes albopictus females to 2.7% of their F1 generation offspring was demonstrated. Progeny of both sexes were infected. Mean virus titers in parent mosquitoes and infected F1 generation adults were 10(4.6) and 10(3.4) plaque forming units/insect, respectively. The La Crosse-infected offspring were randomly distributed among the female parents. After two serial passages in A. albopictus, a marked change occurred in the plaque morphology of the virus but this had no apparent effect on the subsequent vertical transmission rate. In contrast, transovarial transmission did not occur in La Crosse-infected Culex fatigans or in A. albopictus and C. fatigans infected with vesicular stomatitis-Indiana, Cache Valley, Batai, Arumowot, and Itaporanga viruses. Results of this experiment suggest that the La Crosse model might be useful in studying the mechanism of transovarial transmission in additional mosquito species.