Wolbachia pipientisoccurs inAedes aegyptipopulations 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. We did not detect Wolbachia 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 progeny of Las Cruces males mated to Rockefeller females were infected with Wolbachia.

An elusive endosymbiont: DoesWolbachiaoccur naturally inAedes 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, 2019) and more recent tests by the authors…”

“…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 wAlbB infection that occurs natively in Aedes albopictus (Balaji et al, 2019;Carvajal et al, 2019;Coon et al, 2016;Kulkarni et al, 2019), while other studies also detected Wolbachia from supergroups that do not normally occur within Diptera (Carvajal et al, 2019;Thongsripong et al, 2018). Most evidence is limited to molecular detection, and not all studies claim to have discovered an active infection.…”

“…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, 2018;Walker et al, 2011). An A. aegypti population from Las Cruces, New Mexico, USA, was established in the laboratory in September 2018 (Kulkarni et al, 2019) 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, 2017 aegypti (Axford et al, 2016) were included as negative and positive controls, respectively, in each assay.…”

“…TaqMan probe assays were performed as described previously Mee et al, 2015), targeting the 16S rDNA (Supporting Information Appendix S1). We also performed conventional PCR with 16S rDNA and gatB primers following methods described by the authors of the original study (Kulkarni et al, 2019). Finally, LAMP assays were performed using our protocol (Jasper et al, 2019) but with primers used to diagnose Wolbachia infections by the original study (Kulkarni et al, 2019).…”

“…We also performed conventional PCR with 16S rDNA and gatB primers following methods described by the authors of the original study (Kulkarni et al, 2019). Finally, LAMP assays were performed using our protocol (Jasper et al, 2019) but with primers used to diagnose Wolbachia infections by the original study (Kulkarni et al, 2019). From analyses of 72 individuals from both generations with the three molecular assays, zero were infected (Supporting Information Appendix S2).…”