Wolbachia 16S rRNA haplotypes detected in wild Anopheles stephensi in eastern Ethiopia

Abstract

Background About two out of three Ethiopians are at risk of malaria, a disease caused by the parasites Plasmodium falciparum and Plasmodium vivax. Anopheles stephensi, an invasive vector typically found in South Asia and the Middle East, was recently found to be distributed across eastern and central Ethiopia and is capable of transmitting both P. falciparum and P. vivax. The detection of this vector in the Horn of Africa (HOA) coupled with widespread insecticide resistance requires that new methods of vector control be investigated in order to control the spread of malaria. Wolbachia, a naturally occurring endosymbiotic bacterium of mosquitoes, has been identified as a potential vector control tool that can be explored for the control of malaria transmission. Wolbachia could be used to control the mosquito population through suppression or potentially decrease malaria transmission through population replacement. However, the presence of Wolbachia in wild An. stephensi in eastern Ethiopia is unknown. This study aimed to identify the presence and diversity of Wolbachia in An. stephensi across eastern Ethiopia. Methods DNA was extracted from An. stephensi collected from eastern Ethiopia in 2018 and screened for Wolbachia using a 16S targeted PCR assay, as well as multilocus strain typing (MLST) PCR assays. Haplotype and phylogenetic analysis of the sequenced 16S amplicons were conducted to compare with Wolbachia from countries across Africa and Asia. Results Twenty out of the 184 mosquitoes screened were positive for Wolbachia, with multiple haplotypes detected. In addition, phylogenetic analysis revealed two superclades, representing Wolbachia supergroups A and B (bootstrap values of 81 and 72, respectively) with no significant grouping of geographic location or species. A subclade with a bootstrap value of 89 separates the Ethiopian haplotype 2 from other sequences in that superclade. Conclusions These findings provide the first evidence of natural Wolbachia populations in wild An. stephensi in the HOA. They also identify the need for further research to confirm the endosymbiotic relationship between Wolbachia and An. stephensi and to investigate its utility for malaria control in the HOA. Graphical Abstract

Confirmation of the presence of Anopheles stephensi among internally displaced people’s camps and host communities in Aden city, Yemen

“…The haplotype from Yemen grouped with the sole sequence from Djibouti and several from Ethiopia [ 41 ], with reasonable bootstrap support, suggesting possible commonality of origin. However, it should be noted that this clustering was based on a single shared nucleotide variant, which separated the haplotypes on this node from others on the major branch.…”

Wolbachia and Asaia Distribution among Different Mosquito Vectors Is Affected by Tissue Localization and Host Species

“…In all of the anopheline populations analyzed, we never found the presence of Wolbachia . This is not surprising, since although Wolbachia has been reported to be present in some wild populations of anophelines, the infection frequencies are very low [ 36 , 37 , 38 , 39 ]. On the other hand, we found Asaia in all of these populations, albeit with variable infection frequencies that appeared to be strongly correlated to the geographical location of the mosquito population analyzed.…”

Symbiotic Wolbachia in mosquitoes and its role in reducing the transmission of mosquito-borne diseases: updates and prospects

“…Similarly, other research conducted in Senegal reported the first Wolbachia on-field infection in another species, namely An.funestus , using the 16S rRNA gene and isolating new strains called wAnfu-A and wAnfu-B ( Niang et al, 2018 ). In 2022 Waymire et al detected Wolbachia haplotypes in wild Anopheles stephensi in eastern Ethiopia ( Waymire et al, 2022 ). Despite this evidence, according to a phylogenies screening conducted in 2019 by Chrostek and Gerth on Wolbachia 16S rRNA presence in An.…”

“…On the other hand, Quek et al (2022) found that in the absence of Wolbachia, microfilariae quickly lose their capacity to develop in the mosquito vector because of their inability to break out of their shells and get through the gut wall. They also showed that the enzyme chitinase, essential for microfilariae to leave their shells, was low in Wolbachia-depleted microfilariae, preventing them from leaving their shells.…”