EHDV-2 infection prevalence varies in Culicoides sonorensis after feeding on infected white-tailed deer over the course of Viremia

Authors: MENDIOLA, SANDRA - University Of Georgia; MILLS, MARY - Kansas State University; Maki, Elin; Drolet, Barbara; Wilson, William - Bill; BERGHAUS, ROY - University Of Georgia; STALLKNECHT, DAVID - University Of Georgia; Breitenbach, Jonathan; McVey, David; RUDER, MARK - University Of Georgia

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2019
Publication Date: 4/23/2019
Citation: Mendiola, S.Y., Mills, M.K., Maki, E.C., Drolet, B.S., Wilson, W.C., Berghaus, R., Stallknecht, D.E., Breitenbach, J.E., Mcvey, D.S., Ruder, M.G. 2019. EHDV-2 infection prevalence varies in Culicoides sonorensis after feeding on infected white-tailed deer over the course of Viremia. Viruses. 11:371-385. https://doi.org/10.3390/v11040371.
DOI: https://doi.org/10.3390/v11040371

Interpretive Summary: Epizootic hemorrhagic disease viruses (EHDVs) are transmitted by Culicoides biting midges and cause disease in white-tailed deer and other wild and domestic ruminants in North America. The impact of the amount of virus in the deer's blood and how long it persists on the ability of midges to become infected when blood-feeding on the deer is not well characterized. To examine this, five white-tailed deer were experimentally infected with EHDV-2 and midges were allowed to feed on deer at 3, 5, 7, 10, 12, 14, 18, and 24 days post infection (dpi). Blood virus titers at these time points and the number of midges that subsequently became infected midges were determined. We found that increases in deer EHDV blood titers significantly increased both the likelihood that midges would successfully acquire EHDV and the proportion of midges that reached the titer threshold believed necessary for the midge to then transmit the virus to another host when it blood feeds again. Midges even became infected at days 18 and 24 when we could no longer detect infectious virus in the blood. The ability of deer with low amounts of virus in their blood to serve as a source of EHDV for blood-feeding midges should be explored further to better understand its potential epidemiological significance.

Technical Abstract: Epizootic hemorrhagic disease viruses (EHDVs) are arboviral pathogens of white-tailed deer and other wild and domestic ruminants in North America. Transmitted by various species of Culicoides, EHDVs circulate wherever competent vectors and susceptible ruminant host populations co-exist. The impact of variation in the level and duration of EHDV viremia in white-tailed deer (Odocoileus virginianus) on Culicoides infection prevalence is not well characterized. Here we examined how infection prevalence in a confirmed North American vector of EHDV-2 (Culicoides sonorensis) varies in response to fluctuations in deer viremia. To accomplish this, five white-tailed deer were experimentally infected with EHDV-2 and colonized C. sonorensis were allowed to feed on deer at 3, 5, 7, 10, 12, 14, 18, and 24 days post infection (dpi). Viremia profiles in deer were determined by virus isolation and titration at the same time points. Blood-fed Culicoides were assayed for virus after a 10-day incubation (27 C) period. We found that increases in deer EHDV blood titers significantly increased both the likelihood that midges would successfully acquire EHDV and the proportion of midges that reached the titer threshold for transmission competence. Unexpectedly, we identified four infected midge samples (three individuals and one pool) after feeding on one deer 18 and 24 dpi, when viremia was no longer detectable by virus isolation. The ability of ruminants with low-titer viremia to serve as a source of EHDV for blood-feeding Culicoides should be explored further to better understand its potential epidemiological significance.