Molecular detection and characterization of Rift Valley fever virus in arthropod vectors in Nigeria

Rift Valley fever virus (RVFV) is a zoonotic arthropod-borne virus infecting mostly livestock, and sometimes, humans across Africa. It is transmitted primarily by mosquitoes, and occasionally, other arthropod vectors. In this study, arthropod vectors were trapped in Anambra, Benue, Borno and Sokoto States of Nigeria, sorted and pooled according to genera. These vector pools (n = 32), including mosquito (Culex = 17, Aedes = 2, Anopheles = 3 and Mansonia = 3), Culicoides (n = 4) and Phlebotomus (n = 3), were analysed for RVFV using Reverse Transcriptase-nested Polymerase Chain Reaction (RT-nPCR). The RVFV-positive samples were Sanger-sequenced, and the sequence data subjected to nBLAST search, phylogenetic analysis and genotyping. Overall, RVFV was identified in four pools, including one each of Culex, Mansonia, Culicoides and Phlebotomus species. The identified RVFV sequences were closely related, with nucleotide sequence identity of 98.5–99.8 %. Furthermore, phylogenetic analysis showed that they clustered with other Nigerian sequences obtained from humans and domestic ruminants, and with the Ugandan Smithburn strain, but differed from other West African reference strains. Genotyping analysis classified them into Lineage-K. This first molecular detection and characterization of RVFV in arthropod vectors in Nigeria confirms its presence in these insects, highlighting the need for effective vector control to avoid RVFV transmission to humans and susceptible animals in the country.