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

Abstract

Wolbachia are maternally inherited endosymbiotic bacteria found within many insect species. Aedes mosquitoes experimentally infected with Wolbachia are being released into the field for Aedes‐borne disease control. These Wolbachia infections induce cytoplasmic incompatibility which is used to suppress populations through incompatible matings or replace populations through the reproductive advantage provided by this mechanism. However, the presence of naturally occurring Wolbachia in target populations could interfere with both population replacement and suppression programs depending on the compatibility patterns between strains. Aedes aegypti were thought to not harbor Wolbachia naturally but several recent studies have detected Wolbachia in natural populations of this mosquito. We therefore review the evidence for natural Wolbachia infections in A. aegypti to date and discuss limitations of these studies. We draw on research from other mosquito species to outline the potential implications of natural Wolbachia infections in A. aegypti for disease control. To validate previous reports, we obtained a laboratory population of A. aegypti from New Mexico, USA, that harbors a natural Wolbachia infection, and we conducted field surveys in Kuala Lumpur, Malaysia, where a natural Wolbachia infection has also been reported. However, we were unable to detect Wolbachia in both the laboratory and field populations. Because the presence of naturally occurring Wolbachia in A. aegypti could have profound implications for Wolbachia‐based disease control programs, it is important to continue to accurately assess the Wolbachia status of target Aedes populations.

Metagenomic analysis of Aedes aegypti and Culex quinquefasciatus mosquitoes from Grenada, West Indies

“…In Grenada, C. quinquefasciatus was found to have an abundant population of Wolbachia among their bacterial microbiota (62.79% REA) while the A. aegypti population was not found to carry Wolbachia. This is consistent with other studies in which A. aegypti is rarely, if ever, infected with Wolbachia naturally, whereas C. quinquefasciatus is infected throughout its range and in most individual mosquitoes tested [89][90][91].…”

Systematic Review of Wolbachia Symbiont Detection in Mosquitoes: An Entangled Topic about Methodological Power and True Symbiosis

“…aegypti transfected with Wolbachia to replace the natural population to one that is refractory to several arboviruses [23]; II-the second approach is conducted by releasing male mosquitoes infected with Wolbachia seeking to induce CI and reduce the mosquito population [38]. To effectively deploy either strategy, researchers require precise information about any potential target mosquito species infected naturally by Wolbachia before and during any intervention, since it might have unexpected effects on the strategy employed [103].…”

“…aegypti, but the majority used only diagnostic amplicon-based molecular tools [51,[54][55][56][57][58] (Supplementary Material). Two studies went further and analyzed the presence of Wolbachia through maternal transmission and electron microscopy [45,52], but several criticisms have been made due to the lack of methodological consistency or experimental reproducibility issues [103]. Thongsripong et al, 2018 and Carvajal et al, 2019 detected Wolbachia belonging to supergroups C and D in Ae.…”

“…Some species investigated in this review were reported both negative and positive for Wolbachia infection. In some cases, contaminated samples, misidentified species or low sensitivity of the technique used to detect Wolbachia molecules or cells can lead to divergent results regarding the presence of the bacteria in a given species/population [103]. However, this discrepancy can also be a result of the host-parasite population dynamics itself.…”

“…aegypti and An. gambiae are two epidemiological relevant species in which the presence of Wolbachia has been investigated by several studies [46,103]. So far, six Ae.…”