Native Wolbachia infection dynamics across Aedes albopictus (Diptera: Culicidae) populations in Hawai'i

Aedes albopictus, an important vector of arboviruses such as dengue, chikungunya, and Zika, is a widespread invasive mosquito species in the Pacific Islands Countries and Territories, including Hawai'i. Wolbachia, an endosymbiotic bacterium, widely used for mosquito control through its cytoplasmic incompatibility and pathogen blocking properties. Two Wolbachia strains, wAlbA and wAlbB, naturally inhabit Aedes albopictus unlike Aedes aegypti. However, their infection patterns in Hawai'i remain poorly characterized and may influence the success of future Wolbachia-based control efforts.

Using quantitative PCR, we characterized the Wolbachia infection status of Ae. albopictus collected from two Hawaiian Islands: O'ahu and the Island of Hawai'i. We assessed the influence of sex, island, temperature, and precipitation on the prevalence and density of wAlbA and wAlbB, as well as interactions between the two strains.

Overall, 98.5% (N = 399) of individuals were infected with Wolbachia. All infected specimens carried wAlbB, but only 28.6% were superinfected with wAlbA. Infection dynamics were strongly sex-specific, with females significantly more likely to harbor wAlbA, and Wolbachia density was also significantly higher in females. The prevalence of wAlbA was associated with temperature and precipitation at the collection site. However, wAlbB prevalence varied with the island and precipitation. In superinfected individuals, wAlbB consistently exhibited higher density than wAlbA, while wAlbB density was higher in superinfected individuals than in those with wAlbB mono-infection. Interestingly, both strains showed higher densities in females than in males. Strain densities were positively correlated in females but not in males, indicating sex-specific interactions.

By characterizing the Wolbachia infection dynamics of Ae. albopictus populations in Hawai'i, these findings establish an important baseline for biocontrol efforts. We demonstrate that Ae. albopictus mosquitoes in Hawai'i were either superinfected or carry only wAlbB, with lower-than-expected wAlbA infection, which may complicate the design and effectiveness of Wolbachia-based control strategies. Our results highlight that future population suppression projects involving Wolbachia and cytoplasmic incompatibility in Hawai'i must take into account varying patterns of Wolbachia infection in the region prior to biocontrol strategy development and implementation.