Vector competence of biting midges and mosquitoes for Shuni virus.

Background Shuni virus (SHUV) is an orthobunyavirus that belongs to the Simbu serogroup. SHUV was isolated from diverse species of domesticated animals and wildlife, and is associated with neurological disease, abortions, and congenital malformations. Recently, SHUV caused outbreaks among ruminants in Israel, representing the first incursions outside the African continent. The isolation of SHUV from a febrile child in Nigeria and seroprevalence among veterinarians in South Africa suggests that the virus may have zoonotic potential as well. The high pathogenicity, extremely broad tropism, potential transmission via both biting midges and mosquitoes, and zoonotic features of SHUV require further investigation. This is important to accurately determine the risk for animal and human health, and to facilitate preparations for potential epidemics. To gain first insight into the potential involvement of biting midges and mosquitoes in SHUV transmission we have investigated the ability of SHUV to infect two species of laboratory-colonised biting midges and two species of mosquitoes. Methodology/Principal findings Culicoides nubeculosus, C. sonorensis, Culex pipiens pipiens, and Aedes aegypti were orally exposed to SHUV by providing an infectious blood meal. Biting midges showed high infection rates of approximately 40%-60%, whereas infection rates of mosquitoes were only 0-2%. Moreover, successful dissemination in both species of biting midges and no evidence for transmission by orally exposed mosquitoes was found. Conclusions/Significance The results of this study suggest that different species of Culicoides midges are efficient in SHUV transmission, while the involvement of mosquitoes has not been supported. Author summary Arthropod-borne (arbo)viruses are notorious for causing unpredictable and large-scale epidemics and epizootics. Apart from viruses such as West Nile virus and Rift Valley fever virus that are well-known to cause a significant impact on human and animal health, many arboviruses remain neglected. Shuni virus (SHUV) is a neglected virus with zoonotic characteristics that was recently associated with severe disease in livestock and wildlife. Isolations from field-collected biting midges and mosquitoes suggests that SHUV may be transmitted by these insects. In this study, four main vectors that transmit other arboviruses were selected to test their susceptibility to SHUV. Laboratory-reared biting midge species (Culicoides nubeculosus and C. sonorensis) and mosquito species (Culex pipiens pipiens and Aedes aegypti) were exposed to SHUV via an infectious blood meal. SHUV was able to successfully disseminate in both biting midge species, whereas no evidence of transmission by both mosquito species was found. Our results suggest that SHUV can be transmitted efficiently by diverse Culicoides species, and thereby that these insects could play a major role in the disease transmission cycle.