Submitted to: Veterinary Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2007
Publication Date: 9/3/2007
Citation: O'Toole, D., Taus, N.S., Montgomery, D.L., Oaks, J.L., Crawford, T.B., Li, H. 2007. Intra-nasal Inoculation of American Bison (Bison bison) with Ovine Herpesvirus-2 (OvHV-2) Reliably Reproduces Malignant Catarrhal Fever. Veterinary Pathology. 44(5):655-662 Interpretive Summary: Sheep-associated malignant catarrhal fever (MCF) is an economically important disease in the North American bison industry. The disease is caused by a herpesvirus termed ovine herpesvirus 2 (OvHV-2). Because of the inability to grow the virus in culture, it constrains transmission studies of MCF in bison and other animals. Recently we defined the OvHV-2 shedding pattern in its natural carrier, sheep, and are now capable of collecting infectious MCF virus from shedding sheep. In this study, nasal secretions collected from OvHV-2-infected sheep during intense shedding periods was used to establish infection in bison. In experiments bison were intra-nasally aerosolized with the sheep nasal secretions containing infectious OvHV-2. All bison aerosolized with sheep nasal secretion containing 10,000 or more OvHV-2 DNA copies developed clinical MCF. This is the first successful reproduction of MCF in bison using a nasal route of exposure. The study confirms field data that bison are more susceptible to MCF than domestic cattle and indicates that bison can be an excellent animal model for MCF research, including MCF pathogenesis studies and vaccine evaluation.
Technical Abstract: Sheep-associated malignant catarrhal fever due to infection with ovine herpesvirus 2 (OvHV-2) is common in commercial herds of American bison (Bison bison). Inability to propagate OvHV-2 in vitro constrains experimental studies of the disease. We sought to establish whether nasal secretions from sheep that shed OvHV-2 might induce the disease in bison, and to define a minimum challenge dose. Fourteen bison were nebulized with sheep nasal sections containing 1,000 -10,000,000 OvHV-2 DNA copies. Most challenged bison (11/14; 78.6%) developed clinical signs at 29 - 52 days post-nebulization (DPN). Mean incubation time was 42.18 (+/- 7.33 SD) days. Using real-time PCR, OvHV-2 DNA was detected in peripheral blood leukocytes at 21-31 DPN. All bison that developed malignant catarrhal fever had antibodies against the MCF group viruses. Gross and histological lesions were typical of the acute disease. There was no morphological evidence of a dose-related difference in the severity or distribution of lesions. This is the first successful reproduction of MCF in bison using a nasal route of exposure. The study confirms field data that experimentally-challenged bison are more susceptible to MCF than domestic cattle. Bison are a pertinent ruminant species in which the pathogenesis of the disease can be investigated.