Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/5/2004
Publication Date: 1/1/2005
Citation: Berezowski, J.A., Appleyard, G.D., Crawford, T.B., Haigh, J., Li, H., Middleton, D.M., O'Connor, B.P., West, K., Woodbury, M. 2005. An outbreak of sheep-associated malignant catarrhal fever in a bison (bison bison) after exposure to sheep at a public auction sale. Journal of Veterinary Diagnostic Investigation. 17:55-58. Interpretive Summary: The study describes the epidemiology of a large outbreak of MCF in multiple premises in Saskatchewan following exposure of bison to sheep at an auction. The data showed that bison exposed to sheep for one day at a bison sale experienced a mortality rate of 26.4% due to MCF over the following 6 months. The epidemiological pattern strongly suggested that brief contact with sheep was responsible for transmission of OvHV-2 and the subsequent outbreak of MCF. None of 1010 in-contact bison on the purchasers' premises developed MCF during the study period. This indicates that bison-to-bison transmission of OvHV-2 plays a negligible role in the natural epidemiology of MCF in this species. The outbreak provides an illustration of the temporal distribution of MCF mortalities expected in bison and an estimate of the time from exposure until death from MCFfollowing a single short exposure to sheep. Commercial bison must be strictly segregated from sheep at all points of the production cycle, including auction marts, in order to reduce losses due to MCF.
Technical Abstract: An outbreak of malignant catarrhal fever (MCF) among bison sold at an auction market was studied for an 18month period. Forty-five of 163 bison submitted for sale from 8 different bison farms died on 7 other destination farms. The outbreak began on the 50th day following the sale, peaked between the 60th and 70th days and ended on the 220th day. Twenty-one dead bison were confirmed to be MCF cases by clinical histories, pathology and detection of ovine herpesvirus-2 DNA in their tissues with PCR assays. Twenty-four dead bison were classified as suspect MCF cases from clinical histories. No cases of MCF were observed among bison remaining on originating farms or resident bison mixed with sale bison on destination farms. There were no sheep reported within 3 km of originating or destination farms, limiting bison exposure to sheep to the auction facility where sheep were present for less than one day. The outbreak provides an illustration of the temporal distribution of MCF mortalities expected in bison and an estimate of the time from exposure until death from malignant catarrhal fever following a single short exposure to sheep. The study provides evidence that bison with MCF do not transmit MCF to other bison.