Wolbachia's Deleterious Impact on Aedes aegypti Egg Development: The Potential Role of Nutritional Parasitism

Abstract

The artificial introduction of the endosymbiotic bacterium, Wolbachia pipientis, into Aedes (Ae.) aegypti mosquitoes reduces the ability of mosquitoes to transmit human pathogenic viruses and is now being developed as a biocontrol tool. Successful introgression of Wolbachia-carrying Ae. aegypti into native mosquito populations at field sites in Australia, Indonesia and Malaysia has been associated with reduced disease prevalence in the treated community. In separate field programs, Wolbachia is also being used as a mosquito population suppression tool, where the release of male only Wolbachia-infected Ae. aegypti prevents the native mosquito population from producing viable eggs, subsequently suppressing the wild population. While these technologies show great promise, they require mass rearing of mosquitoes for implementation on a scale that has not previously been done. In addition, Wolbachia induces some negative fitness effects on Ae. aegypti. While these fitness effects differ depending on the Wolbachia strain present, one of the most consistent and significant impacts is the shortened longevity and viability of eggs. This review examines the body of evidence behind Wolbachia's negative effect on eggs, assesses nutritional parasitism as a key cause and considers how these impacts could be overcome to achieve efficient large-scale rearing of these mosquitoes.

Keywords: Aedes aegypti; Wolbachia; biocontrol; nutritional parasitism.

Figure 1

(a) Female Aedes aegypti organs involved in blood-meal digestion and subsequent egg production. (b) Female Aedes aegypti nutritional and hormonal signals stimulated by blood-meal. JH: juvenile hormone, OEH: ovary ecdysteroidogenic hormone, ILP3: insulin-like peptide 3, Trypsin prot.: Trypsin proteases, TOR: target of rapamycin, S6K: S6 kinase, Vg: vitellogenin, AAs: amino acids, Carbs.: carbohydrates. Green icons indicate metabolites that are modulated by the presence of Wolbachia. Solid arrows indicate metabolite release and delivery, solid arrows with splayed arrowheads indicates two metabolites working synergistically together and dotted arrows indicate upregulation/release of target metabolite. Figure created with BioRender.com.