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

Abstract

The emergence of insecticide resistance in arbovirus vectors is putting the focus on the development of new strategies for control. In this regard, the exploitation of Wolbachia endosymbionts is receiving increasing attention due to its demonstrated effectiveness in reducing the vectorial capacity of Aedes mosquitoes. Here, we describe the establishment of a naïve Wolbachia infection in a wild Aedes albopictus population of eastern Spain through a hybridization approach to obtain males capable of sterilizing wild females. The obtained lines were compared with the Wolbachia donor, Ae. albopictus ARwP, previously artificially infected with Wolbachia wPip, regarding immature and adult survival, female fecundity, egg fertility, and level of induced sterility. Our results did not show significant differences between lines in any of the biological parameters analyzed, indicating the full suitability of the hybrids to be used as a control tool against Ae. albopictus. In particular, hybrid males induced 99.9% sterility in the eggs of wild females without the need for any preliminary treatment. Being harmless to non-target organisms and the environment, the use of this bacterium for the control of Ae. albopictus deserves further exploration. This is especially relevant in areas such as eastern Spain, where this mosquito species has recently spread and may represent a serious threat due to its competence as a vector for dengue, chikungunya, and Zika viruses.

Keywords: Asian tiger mosquito; Wolbachia; arboviruses; cytoplasmic incompatibility; genetic control; genotyping; hybridization; population suppression.

Figure 1

Wolbachia wPip-infected females in Ae. albopictus ARwP_BA and ARwP_BN over 5 subsequent generations since the first cycle of hybridization. ARwP_L: Wolbachia wPip-infected Ae. albopictus from Rome (Italy) [31]; ARwP_BN: wild strain of Ae. albopictus from Barcelona (Spain) infected with Wolbachia wPip from ARwP_L through hybridization; ARwP_BA: aposymbiotic strain of Ae. albopictus obtained in Valencia from the wild strain of Barcelona and then infected with Wolbachia wPip from ARwP_L through hybridization. From G₁ to G₄ (light grey), females were randomly sampled among all emerged adults and checked for wPip infection by PCR (n = 10). At G₅ (dark grey), tested females were born from eggs oviposited by females that had been ascertained to be wPip-positive (n = 20).

Figure 2

Immature survival of Ae. albopictus ARwP_L, ARwP_BA, and ARwP_BN. ARwP_L: Wolbachia wPip-infected Ae. albopictus from Rome (Italy) [31]; ARwP_BN: wild strain of Ae. albopictus from Barcelona (Spain) infected with Wolbachia wPip from ARwP_L through hybridization; ARwP_BA: aposymbiotic strain of Ae. albopictus obtained in Valencia from the wild strain of Barcelona and then infected with Wolbachia wPip from ARwP_L through hybridization. Error bars show the standard error of the mean of three repetitions. Differences between lines were not statistically significant by one-way ANOVA.

Figure 3

Survival curves of male and female adults belonging to Ae. albopictus ARwP_L, ARwP_BA, and ARwP_BN, three lines infected with the same Wolbachia strain through hybridization. ARwP_L: Wolbachia wPip-infected Ae. albopictus from Rome (Italy) [31]; ARwP_BN: wild strain of Ae. albopictus from Barcelona (Spain) infected with Wolbachia wPip from ARwP_L through hybridization; ARwP_BA: aposymbiotic strain of Ae. albopictus obtained in Valencia from the wild strain of Barcelona and then infected with Wolbachia wPip from ARwP_L through hybridization. In both sexes, differences between lines were not statistically significant by log-rank (Mantel–Cox) test.

Figure 4

Female fecundity (left) and egg fertility (right) in Ae. albopictus ARwP_L, ARwP_BA, and ARwP_BN. ARwP_L: Wolbachia wPip-infected Ae. albopictus from Rome (Italy) [31]; ARwP_BN: wild strain of Ae. albopictus from Barcelona (Spain) infected with Wolbachia wPip from ARwP_L through hybridization; ARwP_BA: aposymbiotic strain of Ae. albopictus obtained in Valencia from the wild strain of Barcelona and then infected with Wolbachia wPip from ARwP_L through hybridization. Error bars show the standard error of the mean (SEM) of three biological replicates, each containing 19–20 fed females. In both cases, values were not significantly different by one-way ANOVA.

Figure 5

Egg fertility (when Ae. albopictus B_N females were crossed with Ae. albopictus males ARwP_BN, ARwP_BA, and B_N). B_N: wild strain of Ae. albopictus from Barcelona colonized in Valencia (Spain); ARwP_BN: wild strain of Ae. albopictus from Barcelona (Spain) infected with Wolbachia wPip from ARwP_L through hybridization; ARwP_BA: aposymbiotic strain of Ae. albopictus obtained in Valencia from the wild strain of Barcelona and then infected with Wolbachia wPip from ARwP_L through hybridization. Error bars show the SEM of three biological replicates. The mean egg fertility was found to differ significantly between crosses by one-way ANOVA.