A bacterium against the tiger: further evidence of the potential of noninundative releases of males with manipulated Wolbachia infection in reducing fertility of Aedes albopictus field populations in Italy

Abstract

BACKGROUND Incompatible insect technique (IIT) is a population suppression approach based on the release of males with manipulated Wolbachia infection inducing egg inviability in wild females. We here present results of multiple field releases of incompatible ARwP males carried out in 2019 in a 2.7‐ha green area within urban Rome (Italy) to assess the effect on Aedes albopictus egg viability. Data are compared with results obtained in 2018, when the approach was tested for the first time in Europe. RESULTS An average of 4674 ARwP males were released weekly for 7 weeks, resulting in a mean ARwP:wild male ratio of 1.1:1 (versus 0.7:1 in 2018). Egg‐viability dynamics in ovitraps significantly varied between treated and control sites, with an estimated overall reduction of 35% (versus 15% in 2018). The estimated proportion of females classified as mated with ARwP males was 41.8% and the viability rate of eggs laid by these females (9.5%) was on average significantly lower than that of females only mated with wild males (87.8%); however, high variability in fertility was observed. Values of ARwP male competitiveness were 0.36 and 0.73 based on the overall viability rate of eggs in ovitraps and on female fertility, respectively; thus, well above the conventional 0.2 threshold for an effective suppressive impact in the field. CONCLUSIONS Results further support the potential of IIT as a tool to contribute to Ae. albopictus control in the urban context, stressing the need for larger field trials to evaluate the cost‐efficacy of the approach in temperate regions. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Wolbachia Infection through Hybridization to Enhance an Incompatible Insect Technique-Based Suppression of Aedes albopictus in Eastern Spain

“…However, protocols to eliminate female contamination need to be considered [ 37 ], and all the possible safety concerns regarding the release of Wolbachia -infected mosquitoes must be evaluated. After that, small-scale trials under open field conditions should be implemented to demonstrate the potential of IIT, favor community acceptance, and help to set appropriate release protocols to achieve efficacy and sustainability [ 38 , 39 ]. All these steps are necessary before moving to large-scale programs that imply specific mass-rearing facilities and major investments.…”

“…albopictus and Ae. aegypti in different areas of the world, either alone [ 31 , 36 , 37 , 38 , 39 , 40 , 41 ] or in combination with SIT [ 42 , 43 ], gradually increasing the record of successes achieved.…”

Introduction of invasive mosquito species into Europe and prospects for arbovirus transmission and vector control in an era of globalization

“…albopictus with a manipulated AR w P strain Wolbachia induced egg inviability in female mosquitoes which prevents the risk of exotic arbovirus transmission. This population suppression approach is referred as incompatible insect technique [ 132 , 133 ]. The combination of Wolbachia -based incompatible insect technique and radiation-based sterile insect technique can be used for population suppression of Ae.…”

Molecular Detection, Characterization, and Temperature-Dependence of Wolbachia Infections in Field Populations of <em>Aedes albopictus</em> (Diptera: Culicidae) Mosquitoes in Greece

“…In addition to the naturally occurring Wolbachia strains in Ae. albopictus, wAlbA and wAlbB, several Wolbachia transfections have been explored in the species, including: (a) stable transfection with the wMel strain from Drosophila melanogaster, which showed positive results in blocking DENV and CHIKV transmission [28,29], (b) the wAu strain from Drosophila simulans, which displayed resistance to Zika and DENV with a moderate fitness cost to the mosquitoes [30], and (c) the wPip strain from Culex pipiens, which led to a reduction in field populations when tripleinfected (wAlbA, wAlbB and wPip) (line HC) or single infected (wPip)(line ARwP) male mosquitoes were released in large field trials [31][32][33][34].…”

“…To our knowledge only one study reports a prevalence of 79% in field population of the Iberian Peninsula, with no information provided about the type of stains (wAlbA or wAlbB) or genotypic diversity [35]. Apart from a field trial of the IIT method with the ARwP line in Italy [34], no Wolbachia-based management practices are currently underway in Europe. Notably, most cases of viruses transmitted by Ae.…”