Species composition, abundance and seasonality of potential Rift Valley fever virus vectors in north-eastern KwaZulu-Natal province, South Africa

Abstract

BACKGROUND: Rift Valley fever virus (RVFV) is endemic in sub-Saharan Africa and the Arabian Peninsula, primarily infecting ruminants such as sheep and cattle and causing high abortion and neonatal mortality rates. Previous studies have indicated hyperendemic circulation of RVFV in north-eastern KwaZulu-Natal (KZN), South Africa. The vectors of RVFV are not well characterized in this area, particularly with respect to species composition, seasonal abundance, and potential vector roles; however, several potential mosquito vector species have been identified. The aim of this study was to describe the species composition, abundance, and seasonal population dynamics of potential RVFV vectors in far north-eastern KZN, in order to identify likely important RVFV vectors in the area. METHODS: -baited tent traps (modified Shannon) were used at pans (temporary wetlands) at each site. Mosquitoes were morphologically identified using available taxonomic keys. A representative subset (approximately 40%) of collected mosquitoes, including potential primary and secondary vector species, were screened for RVFV RNA using real-time reverse transcription PCR. RESULTS: A total of 141,594 mosquitoes consisting of 46 species from 8 genera, including Aedes (2610), Culex (89,143), Mansonia (45,029), and others, were collected. Culex (Culex) tritaeniorhynchus (55,491), Mansonia (Mansonioides) uniformis (35,453), and Culex (Lasioconops) poicilipes (14,192) were the most common species, varying in their relative proportions between sites. Mosquito species diversity and abundance differed across sites, with seasonal peaks occurring from January to April. Overall counts were higher at Namaneni (IRR = 3.30, 95% CI 2.62-4.16), p < 0.001) but lower at Bumbe (IRR = 0.35, 95% CI 0.23-0.54, p < 0.001), compared to Mpala. All 55,113 screened mosquitoes tested negative for RVFV. CONCLUSIONS: Multiple potential RVFV vectors, such as Cx. tritaeniorhynchus, Cx. poicilipes, Aedes (Neomelaniconion) circumluteolus, Aedes (Neo.) mcintoshi, and Aedes (Aedimorphus) durbanensis, were found to be present in relatively high numbers and could play an important role in both endemic and epidemic RVFV transmission.