Infertility and fecundity loss of Wolbachia-infected Aedes aegypti hatched from quiescent eggs is expected to alter invasion dynamics.

The endosymbiotic bacterium Wolbachia shows viral blocking in its mosquito host, leading to its use in arboviral disease control. Releases with Wolbachia strains wMel and wAlbB infecting Aedes aegypti have taken place in several countries. Mosquito egg survival is a key factor influencing population persistence and this trait is also important when eggs are stored prior to releases. We therefore tested the viability of mosquitoes derived from Wolbachia wMel and wAlbB-infected as well as uninfected eggs after long-term storage under diurnal temperature cycles of 11–19°C and 22–30°C. Eggs stored at 11–19°C had higher hatch proportions than those stored at 22–30°C. Adult Wolbachia density declined when they emerged from eggs stored for longer, which was associated with incomplete cytoplasmic incompatibility (CI) when wMel-infected males were crossed with uninfected females. Females from stored eggs at both temperatures continued to show perfect maternal transmission of Wolbachia, but storage reduced the fecundity of both wMel and wAlbB-infected females relative to uninfected mosquitoes. Furthermore, we found a very strong negative impact of the wAlbB infection on the fertility of females stored at 22–30°C, with almost 80% of females hatching after 11 weeks of storage being infertile. Our findings provide guidance for storing Wolbachia-infected A. aegypti eggs to ensure high fitness adult mosquitoes for release. Importantly, they also highlight the likely impact of egg quiescence on the population dynamics of Wolbachia-infected populations in the field, and the potential for Wolbachia to suppress mosquito populations through cumulative fitness costs across warm and dry periods, with expected effects on dengue transmission. Author summary: The endosymbiont bacterium, Wolbachia, has been successfully established in natural Aedes aegypti populations to help suppress the transmission of arboviral diseases such as dengue. The fertility of infected mosquitoes experiencing a quiescent egg stage will influence the efficiency of mosquito releases when mass-reared eggs are stored and may also influence invasion. We tested stored eggs with the wMel or wAlbB infections and found that females derived from eggs stored in a warm environment had reduced fecundity. We also discovered a novel and strong fertility cost on wAlbB-infected A. aegypti, in that a high proportion of females became infertile even though they mated successfully, which was determined by the period when mosquito eggs were quiescent. This effect across life stages was not evident when eggs were stored under cooler conditions and represents the first time that Wolbachia was found to induce female infertility independent of cytoplasmic incompatibility, pointing to a likely additional phenotypic effect of Wolbachia affecting dengue transmission. [ABSTRACT FROM AUTHOR]