Culicoides-virus interactions: infection barriers and possible factors underlying vector competence

Authors: MILLS, MARY - Kansas State University; MICHEL, KRISTIN - Kansas State University; RUDER, MARK - University Of Georgia; PFANNENSTIEL, ROBERT - Animal And Plant Health Inspection Service (APHIS); VERONESI, EVA - University Of Zurich; Nayduch, Dana

Submitted to: Current Opinion in Insect Science
Publication Type: Review Article
Publication Acceptance Date: 5/1/2017
Publication Date: 5/5/2017
Citation: Mills, M., Michel, K., Ruder, M., Pfannenstiel, R., Veronesi, E., Nayduch, D. 2017. Culicoides-virus interactions: infection barriers and possible factors underlying vector competence. Current Opinion in Insect Science. 22:7-15.

Interpretive Summary: In the United States, Culicoides midges transmit viruses such as Bluetongue Virus and Epizootic Hemorrhagic Disease Virus. These viruses are economically important because they cause disease in livestock such as sheep and wildlife such as deer. Midges acquire these viruses when they feed on the blood of infected animals and subsequently can transmit viruses to naïve hosts. However, not all midges become infected after feeding on virus in the blood meal, which indicates that the midge itself has barriers to infection. These barriers underlie the midge’s ability to harbor and transmit viruses, a phenomenon known as vector competence. A limited number of studies have investigated the interactions between these viruses and midges. This includes studies of the dynamic changes in virus abundance and prevalence over the infection time course after midges ingest viruses in the blood meal. These dynamics are, in part, dictated by infection and escape barriers in the gut of the midge. This review summarizes the events that occur during the course of virus infection within the midge. Essential barriers to infection and virus dissemination in the midge are highlighted, and include those that can be inherited (genetic) and those that are extrinsic (environmental, such as gut microflora). Modern molecular tools and techniques, generated in part by USDA-ARS scientists and now available for studying Culicoides midges, gives researchers the opportunity to further investigate factors contributing to vector competence. Identification of processes, factors and components that are important to the midge’s vector competence for virus helps in revealing targets for blocking or controlling transmission.

Technical Abstract: In the United States, Culicoides midges vector arboviruses of economic importance such as Bluetongue Virus and Epizootic Hemorrhagic Disease Virus. A limited number of studies have demonstrated the complexities of midge-virus interactions, including dynamic changes in virus titer and prevalence over the infection time course. These dynamics are, in part, dictated by mesenteron infection and escape barriers. This review summarizes the overarching trends in viral titer and prevalence throughout the course of infection. Essential barriers to infection and dissemination in the midge are highlighted, along with heritable and extrinsic factors that likely contribute to these barriers. Next generation molecular tools and techniques, now available for Culicoides midges, gives researchers the opportunity to test how these factors contribute to vector competence.