Wolbachia Density and Cytoplasmic Incompatibility in Aedes albopictus: Concerns with Using Artificial Wolbachia Infection as a Vector Suppression Tool

Abstract

The mosquito Aedes albopictusi is a competent vector of harmful human pathogens, including viruses causing dengue and chikungunya. Cytoplasmic incompatibility (CI) induced by endosymbiotic Wolbachia can be used to produce functionally sterile males that can be released in the field as a suppression tool against this mosquito. Because the available sexing methods are not efficient enough to avoid unintentional release of a few transinfected females, we assessed the CI pattern in crosses between wPip Wolbachia-transinfected (ARwP) females and wild-type males of Ae. albopictus in this study. Quantitative polymerase chain reaction was used to monitor the titer of the Wolbachia strains that naturally infect Ae. albopictus, that is, wAlbA and wAlbB, in age-controlled males and females. Data were coupled with incompatibility level detected when the above-mentioned males were crossed with ARwP females. Wolbachia infection titer was also monitored in samples of wild caught males. Incompatibility level was positively correlated only with wAlbA density. Crosses between wild-type males having very low wAlbA density (<0.001 wAlbA/actin copy numbers) and ARwP females were partially fertile (CIcorr = 68.06 ± 6.20). Individuals with low wAlbA titer were frequently found among sampled wild males (30%–50% depending on the site and period). ARwP males can be as considered as a very promising tool for suppressing Ae. albopictus. However, crosses between wild males having low wAlbA density and ARwP females may be partially fertile. In the case of local establishment of the transinfected mosquito line, this occurrence may favor the replacement of the wild-type mosquitoes with the ARwP line, thus reducing the long-term efficacy of incompatible insect technique. Various alternative strategies have been discussed to prevent this risk and to exploit Wolbachia as a tool to control Ae. albopictus.

An elusive endosymbiont: Does Wolbachia occur naturally in Aedes aegypti?

“…Below, we discuss the limitations of current studies and describe the evidence needed to confirm the presence of putative natural Wolbachia infections. (Calvitti et al, 2015;Tortosa et al, 2010). High Wolbachia densities in the ovaries are also consistent with a true infection, since maternal transmission requires infection of the germ line (Veneti, Clark, Karr, Savakis, & Bourtzis, 2004) but not somatic tissues, although Wolbachia often occupy somatic tissues (Dobson et al, 1999).…”

“…These patterns are summarized in Figure , although crossing patterns in nature are likely to be more complex. Natural Wolbachia infections can have heterogeneous densities and frequencies in populations (Calvitti, Marini, Desiderio, Puggioli, & Moretti, ), making compatibility patterns hard to predict. Crosses may differ in the strength of incompatibility in different directions (O'Neill and Paterson, , Joubert et al, ; Sinkins et al, ), and there are also environment‐dependent effects on cytoplasmic incompatibility including adult age (Kittayapong, Mongkalangoon, Baimai, & O'Neill, ) and temperature (Ross, Ritchie, Axford, & Hoffmann, ).…”

Wolbachia pipientis occurs in Aedes aegypti populations in New Mexico and Florida, USA

“…However, Wolbachia has not been detected in wild Ae. albopictus (Ahantarig, Trinachartvanit, & Kittayapong, 2008;Calvitti, Marini, Desiderio, Puggioli, & Moretti, 2015). In the study by Coon et al of Wolbachia in the Ae.…”

A bacterium against the tiger: preliminary evidence of fertility reduction after release of Aedes albopictus males with manipulated Wolbachia infection in an Italian urban area

“…albopictus with a foreign Wolbachia strain ( w Pip) obtained from Culex pipiens . The new line (AR w P) was shown to induce full cytoplasmic incompatibility when crossed with wild‐type females and full fertility when crossed with AR w P females, and to be stable over time . Notably, AR w P males demonstrated increased male mating competitiveness when competing with wild‐type males in large enclosures in the field .…”

“…30 The new line (ARwP) was shown to induce full cytoplasmic incompatibility when crossed with wild-type females and full fertility when crossed with ARwP females, and to be stable over time. 23,31 Notably, ARwP males demonstrated increased male mating competitiveness when competing with wild-type males in large enclosures in the field. 32 Moreover, the transinfected line also showed full suitability for the mass-rearing and sexing protocols needed to exploit it in IIT control schemes.…”