Venereal transmission of vesicular stomatitis virus by Culicoides sonorensis midges

Authors: ROZO-LOPEZ, PAULA - Kansas State University; LONDONO-RENTERIA, BERLIN - Kansas State University; Drolet, Barbara

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2020
Publication Date: 4/24/2020
Citation: Rozo-Lopez, P., Londono-Renteria, B., Drolet, B.S. 2020. Venereal transmission of vesicular stomatitis virus by Culicoides sonorensis midges. Pathogens. 9(4):316. https://doi.org/10.3390/pathogens9040316.
DOI: https://doi.org/10.3390/pathogens9040316

Interpretive Summary: Culicoides sonorensis biting midges are well-known agricultural pests and are able to transmit vesicular stomatitis virus (VSV) to cattle, horses and swine. Understanding and predicting VSV outbreaks is difficult because it infects multiple animals, it can be transmitted by direct contact and contaminated surfaces in addition to insect bites, and it can be transmitted by more than one species of insect. To better understand how the virus may be maintained in insect populations, we examined whether virus could pass between male and female midges during mating. Our results showed that VSV-infected females could venereally transmit virus to uninfected naïve males and infected males could venereally transmit virus to uninfected naïve females. Using staining techniques, examining dissected reproductive organs, and observing midge mating behavior, we were able to determine relevant anatomical sites for virus location and to hypothesize the potential mechanism for VSV transmission in midges through copulation.

Technical Abstract: Culicoides sonorensis biting midges are well-known agricultural pests and transmission vectors of arboviruses such as vesicular stomatitis virus (VSV). The epidemiology of VSV is complex and encompasses a broad range of vertebrate hosts, multiple routes of transmission, and diverse vector species. In temperate regions, viruses can overwinter in the absence of infected animals through unknown mechanisms, to reoccur the next year. Non-conventional routes for VSV vector transmission may help explain viral maintenance in midge populations during inter-epidemic periods and times of adverse conditions for bite transmission. In this study, we examined whether VSV could be transmitted venereally between male and female midges. Our results showed that VSV-infected females could venereally transmit virus to uninfected naïve males at a rate as high as 76.3% (qRT-PCR), 31.6% (virus isolation) during the third gonotrophic cycle. Additionally, VSV-infected males could venereally transmit virus to uninfected naïve females at a rate as high as 76.6% (qRT-PCR), 49.2% (virus isolation). Immunofluorescent staining of micro-dissected reproductive organs, immunochemical staining of midge histological sections, examination of internal reproductive organ morphology, and observations of mating behaviors were used to determine relevant anatomical sites for virus location and to hypothesize the potential mechanism for VSV transmission in C. sonorensis midges through copulation.