Transovarial transmission of arboviruses by mosquitoes: a review.

One interesting aspect of mosquito-borne arboviruses is their endemic persistence, espeically during adverse climatic conditions in the temperate zones. The hypothesis that transovarial transmission of alpha- and flaviviruses by their respective mosquito vectors could serve as an overwintering mechanism has been proposed; however, experimental data in support of this hypothesis are not very convincing. Recently, some of the California encephalitis group arboviruses have been shown to be transmitted transovarially by Aedes species mosquitoes, and studies indicate that this mechanism contributes to the natural maintenance cycle of these viruses. Finally, consideration is given to the possibility that transovarial transmission may be unique to the California encephalitis group arboviruses and may be related to their association with a vector that overwinters in the egg stage of its life cycle.