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

Abstract

The mosquitoes Aedes aegypti (L.) and Ae. albopictus Skuse are the major vectors of dengue, Zika, yellow fever, and chikungunya viruses worldwide. Wolbachia, an endosymbiotic bacterium present in many insects, is being utilized in novel vector control strategies to manipulate mosquito life history and vector competence to curb virus transmission. Earlier studies have found that Wolbachia is commonly detected in Ae. albopictus but rarely detected in Ae. aegypti. In this study, we used a two‐step PCR assay to detect Wolbachia in wild‐collected samples of Ae. aegypti. The PCR products were sequenced to validate amplicons and identify Wolbachia strains. A loop‐mediated isothermal amplification (LAMP) assay was developed and used for detecting Wolbachia in selected mosquito specimens as well. We found Wolbachia in 85/148 (57.4%) wild Ae. aegypti specimens from various cities in New Mexico, and in 2/46 (4.3%) from St. Augustine, Florida. Wolbachia was not detected in 94 samples of Ae. aegypti from Deer Park, Harris County, Texas. Wolbachia detected in Ae. aegypti from both New Mexico and Florida was the wAlbB strain of Wolbachia pipientis. A Wolbachia‐positive colony of Ae. aegypti was established from pupae collected in Las Cruces, New Mexico, in 2018. The infected females of this strain transmitted Wolbachia to their progeny when crossed with males of Rockefeller strain of Ae. aegypti, which does not carry Wolbachia. In contrast, none of the progeny of Las Cruces males mated to Rockefeller females were infected with Wolbachia.

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

“…Through these analyses, we demonstrate conclusively that the LC population does not harbor Wolbachia . These results conflict with those from the original study (Kulkarni et al, ) and more recent tests by the authors where Wolbachia is at a high frequency (28/32, 87.5%) in the fourth laboratory generation (Jiannong Xu, personal communication). Although the reason for this conflicting result is unclear, our study emphasizes the need for independent evaluation of Wolbachia infections in A. aegypti .…”

“…These studies report variable infection frequencies in populations and identify infections from several Wolbachia supergroups. Most studies found that the infections detected were closely related to or identical to the w AlbB infection that occurs natively in Aedes albopictus (Balaji et al, ; Carvajal et al, ; Coon et al, ; Kulkarni et al, ), while other studies also detected Wolbachia from supergroups that do not normally occur within Diptera (Carvajal et al, ; Thongsripong et al, ). Most evidence is limited to molecular detection, and not all studies claim to have discovered an active infection.…”

“…Most evidence is limited to molecular detection, and not all studies claim to have discovered an active infection. However, some studies have established laboratory colonies and reported maternal transmission of Wolbachia (Kulkarni et al, ) or the loss of infection through antibiotic treatment (Balaji et al, ).…”

“…We obtained one of these populations with the intention of examining crossing patterns between natural infections and novel infections that are being deployed into the field (Ant et al, ; Walker et al, ). An A. aegypti population from Las Cruces, New Mexico, USA, was established in the laboratory in September 2018 (Kulkarni et al, ) and kindly provided to us by the authors. We received eggs from the third and fourth generations of this population (denoted LC) which were hatched and maintained in our laboratory according to methods described previously (Ross, Axford, Richardson, Endersby‐Harshman, & Hoffmann, ).…”

“…We used molecular approaches to try and confirm Wolbachia infection in the A. aegypti LC strain. According to the authors, this population harbors a natural Wolbachia infection closely related to the w AlbB infection from A. albopictus (Kulkarni et al, ). Real‐time PCR/high‐resolution melt (RT/HRM) assays were performed as previously described (Axford et al, ; Lee, White, Weeks, Hoffmann, & Endersby, ) using primers specific to the w AlbB Wolbachia strain as well as Aedes and A. aegypti ‐specific primers (Supporting Information Appendix ).…”