Abstract
BackgroundWolbachia bacteria are widely distributed throughout terrestrial arthropod species. These bacteria can manipulate reproduction and influence the vector competence of their hosts. Recently, Wolbachia have been integrated into vector control programmes for mosquito management. A number of supergroups and strains exist for Wolbachia, and they have yet to be characterized for many mosquito species. In this study, we examined Wolbachia prevalence and their phylogenetic relationship to other Wolbachia, using mosquitoes collected in Merced County in the Central Valley of California.MethodsAdult mosquitoes were collected from 85 sites in Merced County, California in 2017 and 2018. Traditional and quantitative PCR were used to investigate the presence or absence and the density of Wolbachia, using Wolbachia-specific 16S rRNA and Wolbachia-surface protein (wsp) genes. The supergroup of Wolbachia was determined, and Multilocus Sequence Typing (MLST) by sequencing five housekeeping genes (coxA, gatB, ftsZ, hcpA and fbpA) was also used to determine Wolbachia supergroup as well as strain.ResultsOver 7100 mosquitoes of 12 species were collected: Aedesmelanimon, Ae. nigromaculis, Ae. vexans, Ae. aegypti, Culex pipiens, Cx. stigmatosoma, Cx. tarsalis, Anopheles franciscanus, An. freeborni, An. punctipennis, Culiseta incidens and Cs. inornata. Eight showed evidence of Wolbachia. To our knowledge, this study is the first to report detection of Wolbachia in five of these species (Ae. melanimon, Cx. stigmatosoma, Cx. tarsalis, Cs. incidens and Cs. inornata). Culex pipiens and Cx. stigmatosoma had a high frequency and density of Wolbachia infection, which grouped into supergroup B; Cs. inornata clustered with supergroup A. MLST comparisons identified Cx. pipiens and Cx. stigmatosoma as wPip strain type 9 supergroup B. Six species had moderate to low (< 14%) frequencies of Wolbachia. Four species were negative, Ae. nigromaculis, An. franciscanus, An. freeborni and Ae. aegypti.ConclusionsNew records of Wolbachia detection were found in mosquitoes from Merced County, California. Culex stigmatosoma and Cs. inornata were new records for Wolbachia supergroup B and A, respectively. Other species with Wolbachia occurred with low frequency and low density. Detection of Wolbachia in mosquitoes can be used to inform potential vector control applications. Future study of Wolbachia within Cx. stigmatosoma and Cs. inornata in California and through the range of these species could further explore Wolbachia infection in these two species.
Highlights
Wolbachia bacteria are widely distributed throughout terrestrial arthropod species
Wolbachia pipientis are a monophyletic group of obligate intracellular bacteria that belong to the order Rickettsiales
The objectives of this study were to determine the presence or absence of Wolbachia in twelve mosquito species collected throughout Merced County, and to characterize the Wolbachia supergroup and strain for species with detections
Summary
Wolbachia bacteria are widely distributed throughout terrestrial arthropod species. These bacteria can manipulate reproduction and influence the vector competence of their hosts. Wolbachia-infections have shown other complex host-specific manipulations: they can have increased or decreased rates of reproductive phenotypes; reduced host life-span and egg viability [6, 22]; impact larval survival [23]; decreased female mosquito biting ability [24]; decreased relative abundance of resident bacteria [25]; and in some cases, increased viral susceptibility and host mortality [26, 27]. Artificial infection of this endosymbiont into arthropod vectors has been shown to impact transmission of vector-borne diseases including lymphatic filariasis, West Nile virus, chikungunya, dengue, Zika, and avian malaria [14, 19, 20, 26]
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