Characterization of mosquito host-biting networks of potential Rift Valley fever virus vectors in north-eastern KwaZulu-Natal Province, South Africa

Abstract

Background Rift Valley fever virus (RVFV) is a zoonotic mosquito-borne virus with serious implications for livestock health, human health, and the economy in Africa, and is suspected to be endemic in north-eastern KwaZulu-Natal (KZN), South Africa. The vectors of RVFV in this area are poorly known although several species such as Aedes mcintoshi, Ae. circumluteolus, Ae. durbanensis and Culex poicilipes may be involved. The aim of the study was to determine the blood hosts of potential RVFV mosquito vectors in north-eastern KZN and to characterize the host-biting network. Methods Blood-fed mosquitoes were collected monthly (January 2022 – February 2023) using a backpack aspirator in the vicinity of water bodies and livestock farming households. Additional blood-fed mosquitoes were trapped monthly (November 2019-November 2022) using CO₂-baited CDC miniature light traps and tent traps. Blood-fed mosquitoes were morphologically identified. DNA was extracted from individual mosquitoes and used as templates to amplify the vertebrate cytochrome c oxidase I (COI) and cytochrome b (cytb) genes using conventional PCR. Amplicons were sequenced and queried in GenBank and the Barcode of Life Data systems to identify the blood meal sources and confirm mosquito identifications. All mosquitoes were screened for RVFV using real time RT-PCR. Results We identified the mammalian (88.8%) and avian (11.3%) blood hosts from 409 blood-fed mosquitoes. Aedes circumluteolus (n = 128) made up the largest proportion of collected mosquitoes. Cattle (n = 195) and nyala (n = 61) were the most frequent domestic and wild hosts, respectively. Bipartite network analysis showed that the rural network consisted of more host-biting interactions than the reserve network. Conclusion Several mosquito species including Ae. circumluteolus, and vertebrate blood host species including cattle and nyala could play a central role in RVFV transmission. Future research in this region should focus on these species to better understand RVFV amplification.