Detection of Wolbachia in field-collected Aedes aegypti mosquitoes in metropolitan Manila, Philippines

Abstract

Background Recent reports reveal the presence of Wolbachia in Ae. aegypti . Our study presents additional support for Wolbachia infection in Ae. aegypti by screening field-collected adult mosquitoes using two Wolbachia -specific molecular makers. Methods A total of 672 Ae. aegypti adult mosquitoes were collected from May 2014 to January 2015 in Metropolitan Manila. Each individual sample was processed and screened for the presence of Wolbachia by selected markers, Wolbachia -specific 16S rDNA and its surface protein ( wsp ), under optimized PCR conditions and sequenced. Results Totals of 113 (16.8%) and 89 (13.2%) individual mosquito samples were determined to be infected with Wolbachia using the wsp and 16S rDNA markers, respectively. The Ae. aegpyti wsp sample sequences were similar or identical to five known Wolbachia strains belonging to supergroups A and B while the majority of 16S rDNA sample sequences were similar to strains belonging to supergroup B. Overall, 80 (11.90%) individual mosquito samples showed positive amplifications in both markers and 69% showed congruence in supergroup identification (supergroup B). Conclusions By utilizing two Wolbachia -specific molecular makers, our study demonstrated the presence of Wolbachia from individual Ae. aegypti samples. Our results showed a low Wolbachia infection rate and inferred the detected strains belong to either supergroups A and B. Electronic supplementary material The online version of this article (10.1186/s13071-019-3629-y) contains supplementary material, which is available to authorized users.

An elusive endosymbiont: DoesWolbachiaoccur naturally inAedes aegypti?

“…Species misidentification may also cause false positives if one species harbors Wolbachia and the other does not. Both Teo et al () and Carvajal et al () used identification keys but did not confirm that samples were A. aegypti with molecular approaches. Since A. aegypti and A. albopictus are sympatric in both locations, detections of Wolbachia in A. aegypti could result from species misidentification.…”

“…Several species of filarial nematodes that infect A. aegypti harbor obligate Wolbachia infections from supergroups C and D (Bouchery, Lefoulon, Karadjian, Nieguitsila, & Martin, ). Both Thongsripong et al () and Carvajal et al () detected Wolbachia in A. aegypti that aligned to supergroup C. Carvajal et al () observed substantial diversity in 16S rDNA and wsp sequences, with alignments to supergroups A, B, C, D, and J. Given that Wolbachia from supergroups C, D, and J are not known to occur in Diptera, such diversity is likely explained by contamination from other sources.…”

“…For molecular confirmation of Wolbachia infections, appropriate positive and negative controls are needed. Carvajal et al () used water as a negative control, but this is inadequate because positive detections may be due to amplification of mosquito nDNA. Mosquitoes or other insects of a known infection status, both Wolbachia ‐infected and uninfected, are needed in each assay for confident diagnosis.…”

“…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.…”

An elusive endosymbiont: DoesWolbachiaoccur naturally inAedes 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 wAlbB infection that occurs natively in Aedes albopictus (Coon et al, 2016, Balaji et al, 2019, Carvajal et al, 2019, 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 but some studies established laboratory colonies and have reported maternal transmission of Wolbachia (Kulkarni et al, 2019) and the loss of infection through antibiotic treatment (Balaji et al, 2019).…”