Vector Competence of Selected Mosquito Species in Kenya for Ngari and Bunyamwera Viruses

Abstract

Bunyamwera and Ngari viruses have been isolated from a range of mosquito species in Kenya but their actual role in the maintenance and transmission of these viruses in nature remains unclear. Identification of the mosquito species efficient in transmitting these viruses is critical for estimating the risk of human exposure and understanding the transmission and maintenance mechanism. We determined the vector competence of, Aedes aegypti (L.), Culex quinquefasciatus Say, and Anopheles gambiae Giles for transmission of Bunyamwera and Ngari viruses. Ae. aegypti was moderately susceptible to Bunyamwera virus infection at days 7 and 14. Over 60% of Ae. aegypti with a midgut infection developed a disseminated infection at both time points. Approximately 20% more mosquitoes developed a disseminated infection at day 14 compared with day 7. However, while Ae. aegypti was incompetent for Ngari virus, An. gambiae was moderately susceptible to both viruses with dissemination rates more than double by day 14. Cx. quinquefasciatus was refractory to both Bunyamwera and Ngari viruses. Our results underscore the need to continually monitor emergent arboviral genotypes circulating within particular regions as well as vectors mediating these transmissions to preempt and prevent their adverse effects. The genetic mechanism for species specificity and vector competence owing to reassortment needs further investigation.

Keywords: Bunyamwera virus; Ngari virus; competence; reassortment.