Evaluating the vector competence of Aedes simpsoni sl from Kenyan coast for Ngari and Bunyamwera viruses

BACKGROUND: Bunyamwera(BUNV) and Ngari (NGIV) viruses are arboviruses of medical importance globally, the viruses are endemic in Africa, Aedes(Ae) aegypti and Anopheles(An) gambiae mosquitoes are currently competent vectors for BUNV and NGIV respectively. Both viruses have been isolated from humans and mosquitoes in various ecologies of Kenya. Understanding the risk patterns and spread of the viruses necessitate studies of vector competence in local vector population of Ae. simpsoni sl which is abundant in the coastal region. This study sought to assess the ability of Ae. Simpsoni sl mosquitoes abundant at the Coast of Kenya to transmit these viruses in experimental laboratory experiments. METHODS: Field collected larvae/pupae of Ae. Simpsoni sl mosquitoes from Rabai, Kilifi County, were reared to adults, the first filial generation (F0) females’ mosquitoes were orally exposed to infectious blood meal with isolates of the viruses using the hemotek membrane feeder. The exposed mosquitoes were incubated under insectary conditions and sampled on day 7, 14 and 21days post infection to determine susceptibility to the virus infection using plaque assay. RESULTS: A total of 379 (Bunyamwera virus 255 and Ngari virus 124) Ae. simpsoni sl were orally exposed to infectious blood meal. Overall, the infection rate (IR) for BUNV and NGIV were 2.7 and 0.9% respectively. Dissemination occurred in 5 out 7 mosquitoes with mid-gut infection for Bunyamwera virus and 1 out of 2 mosquitoes with mid-gut infection for Ngari virus. Further, the transmission was observed in 1 out of 5 mosquitoes that had disseminated infection and no transmission was observed for Ngari virus in all days post infection (dpi). CONCLUSION: Our study shows that Ae. simpsoni sl. is a laboratory competent vector for Bunyamwera virus since it was able to transmit the virus through capillary feeding while NGIV infection was restricted to midgut infection and disseminated infection, these finding adds information on the epidemiology of the viruses and vector control plan.