title: Experimental infection of Holstein cows and calves with EHDV‑7 and preliminary evaluation of different inoculation methods.
abstract: Infection of cattle with epizootic haemorrhagic disease (EHD) virus (EHDV) is frequently subclinical, yet reports of disease have increased in recent years. In 2006, a widespread EHDV‑7 epidemic caused disease and economic loss in the Israeli dairy industry. In this study, the main objective was to infect cattle with EHDV‑7 and replicate disease observed in Israel during 2006. Two infection studies were performed. Experiment 1, 4 cows inoculated with intradermal (ID) and subcutaneous (SC) injections with an EHDV‑7 blood inoculum. Experiment 2, 6 calves inoculated using 1 of the following 3 methods (2 calves/method): (1) mammalian cell culture supernatant by ID and SC injection; (2) culture supernatant by ID, SC, and intravenous injection; and (3) bite transmission from Culicoides sonorensis. Further, during experiment 2, C. sonorensis were fed on 4 infected calves (18 days post-inoculation) and processed for virus isolation 10 days later in order to evaluate infectivity of low‑titer viraemia. Three cows had detectable viraemia and all 4 seroconverted. No clinical signs were observed. All 6 calves developed viraemia, peaking 7‑10 dpi and all calves seroconverted. No differences in virus kinetics were observed between the inoculation groups. Calves in group 2 had transiently elevated rectal temperatures but no other clinical abnormalities were observed. The 124 midge pools processed after feeding on calves with low‑titer viraemia were virus isolation negative. Detectable viraemia was more consistent in calves than adult cows. This study demonstrates US‑origin cattle are susceptible to EHDV‑7 infection by multiple inoculation methods; however, as reported in other studies, the disease was not replicated experimentally.
authors.affiliation: Southeastern Cooperative Wildlife Disease Study, Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, GA 30602 USA.
authors.forename: Mark G
authors.initials: MG
authors.lastname: Ruder
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Mead
authors.forename: David E
authors.initials: DE
authors.lastname: Stallknecht
authors.forename: Maor
authors.initials: M
authors.lastname: Kedmi
authors.forename: Eyal
authors.initials: E
authors.lastname: Klement
authors.forename: Justin D
authors.initials: JD
authors.lastname: Brown
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Carter
authors.forename: Elizabeth W
authors.initials: EW
authors.lastname: Howerth
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000821:virology*; D004195:Disease Models, Animal; D005260:Female; D018164:Hemorrhagic Disease Virus, Epizootic; D012088:Reoviridae Infections / Q000662:veterinary*; D014766:Viremia / Q000662:veterinary; D014773:Virology / Q000379:methods