Dengue serotype-2 and sindbis-like viruses circulating in zoophilic mosquitoes at human-wildlife interfaces in Kenya.

Abstract

Zoophilic mosquitoes play an important role in the transmission of arboviruses of medical importance at human-wildlife interfaces, yet arbovirus surveillance efforts have been focused mostly on anthropophilic mosquitoes. Besides pathogen identification, knowing mosquito blood-meal sources aids in identifying disease transmission trends and reservoir hosts during inter-epidemic periods, which can inform appropriate vector control strategies. We morphologically identified mosquito species collected from two game reserves, the Maasai Mara National Reserve (MMNR) and locations near the Shimba Hills National Reserve (SHNR), in Kenya. Subsequently, representative mosquitoes sampled from both sites were identified by cytochrome c oxidase subunit 1 (COI) barcode sequencing. In addition, we identified the vertebrate hosts of mosquito blood-meals by high-resolution melting (HRM) analysis and sequencing of COI, 16S ribosomal RNA, and cytochrome b gene PCR products. Similarly, mosquito arbovirus infections were identified by HRM profiles and sequencing of Alphavirus- and Flavivirus-specific PCR products. Out of 2,858 mosquitoes collected, 51 had blood-meals from seven vertebrate hosts, including humans, domestic and peri-domestic animals, and wildlife (including birds). One Eretmapodites chrysogaster mosquito had fed on both human and hippopotamus blood. Culex was the most abundant mosquito genus, with Culex pipiens being the most abundant species. The Ae. aegypti COI sequences obtained in the study were highly polymorphic. We detected dengue serotype-2 (DENV-2) in Aedes aegypti mosquitoes obtained from the MMNR and the locations near the SHNR. Additionally, DENV-2 virus was detected in Aedes tarsalis and Aedes tricholabis sampled in the MMNR. The dengue infected Ae. tarsalis had fed on bushbuck blood. We also detected a sindbis-like virus in male Cx. pipiens from the MMNR. Our findings highlight the potential risk of sylvatic dengue transmission to humans by zoophilic mosquitoes at human-wildlife interfaces in Africa. As male mosquitoes do not feed on blood, our findings suggest that the novel sindbis-like virus may be maintained in mosquito populations by vertical or environmental transmission