Sexual transmission of Anopheles gambiae densovirus (AgDNV) leads to disseminated infection in mated females

Background Anopheles gambiae densovirus (AgDNV) is an insect-specific, single-stranded DNA virus that infects An. gambiae, the major mosquito species responsible for transmitting malaria parasites throughout Sub-Saharan Africa. AgDNV is a benign virus that is very specific to its mosquito host and therefore has potential to serve as a vector control tool via paratransgenesis (genetic modification of mosquito symbionts) to limit transmission of human pathogens. Prior to being engineered into a control tool, the natural transmission dynamics of AgDNV between An. gambiae mosquitoes needs to be fully understood. Additionally, improved knowledge of AgDNV infection in male mosquitoes is needed. In this study, we examine the tissue tropism of AgDNV in the male reproductive tract and investigate both venereal and vertical transmission dynamics of the virus.

Methods An. gambiae adult males were infected with AgDNV via micro-injection and reproductive tissues collected and assayed for AgDNV using qPCR. Next, uninfected females were introduced to AgDNV-infected or control males and, after several nights of mating, both the spermatheca and female carcass were assessed for venereally transmitted AgDNV. Finally, F1s from this cross were collected and assayed to quantify vertical transmission of the virus.

Results AgDNV infected the reproductive tract of male mosquitoes, including the testes and male accessory glands (MAGs), without affecting mating rates. AgDNV-infected males venereally transmitted virus to females, and these venereally-infected females developed disseminated infection throughout the body. However, AgDNV was not vertically transmitted to F1s resulting from this cross.

Conclusions Infected male releases could be an effective strategy to introduce AgDNV-based paratransgenic tools into naïve populations of An. gambiae females.