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United States Department of Agriculture

Agricultural Research Service

Title: A DEVASTATING OUTBREAK OF MALIGNANT CATARRHAL FEVER IN A BISON FEEDLOT

Authors
item Li, Hong
item Taus, Naomi
item Jones, C - INTERMOUNTAIN BEEF
item Murphy, B - WASHINGTON STATE UNIV.
item Evermann, J - WASHINGTON STATE UNIV.
item Crawford, T - WASHINGTON STATE UNIV.

Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 20, 2005
Publication Date: January 1, 2006
Citation: Li, H., Taus, N.S., Jones, C., Murphy, B., Evermann, J.F., Crawford, T.B. 2006. A devastating outbreak of malignant catarrhal fever in a bison feedlot. Journal of Veterinary Diagnostic Investigation. 18(1):119-123.

Interpretive Summary: Malignant catarrhal fever (MCF) is a frequently fatal, herpesvirus-induced disease in certain ruminant species, such as cattle bison and deer. This study reported a MCF outbreak in a bison feedlot in southern Idaho resulted in a 51.2 % (n = 825) mortality rate among bison, which had been exposed to sheep for 20 days. Diagnosis was made by detection of ovine herpesvirus 2 (sheep-associated MCF virus) DNA in tissues or peripheral blood by PCR, and by histological examination of tissue lesions. Peak losses occurred between 41 and 55 days post-mean exposure time, and reached a maximum of 41 head per day. No known cases of MCF were observed among the 177 head of bison that arrived in the lot 3 1/2 weeks after the departure of the sheep. Of the several thousand head of beef cattle in the lot during the outbreak, only a single case of MCF was identified. This outbreak illustrates: 1) The disease can have a devastating impact on bison under proper exposure conditions; 2) Sheep are the main source of MCF virus transmission, and adolescent sheep between 6 to 9 months of age pose the greatest danger to bison; 3) Bison are significantly more susceptible to MCF than are cattle; 4) Bison with clinical MCF do not serve as a source of virus for transmission of MCF to herdmates; 5) Bison must be kept separated from sheep if serious outbreaks are to be avoided.

Technical Abstract: In early 2003, a malignant catarrhal fever (MCF) outbreak in a bison feedlot in southern Idaho resulted in a 51.2 % (n = 825) mortality rate among bison, which had been exposed to sheep for 20 days. Diagnosis was made by detection of ovine herpesvirus 2 (sheep-associated MCF virus) DNA in tissues or peripheral blood by PCR, and by histological examination of tissue lesions. Peak losses occurred between 41 and 55 days post-mean exposure time (PME), and reached a maximum of 41 head per day. No known cases of MCF were observed among the 177 head of bison that arrived in the lot 3 1/2 weeks after the departure of the sheep. Of the several thousand head of beef cattle in the lot during the outbreak, only a single case of MCF was identified. This outbreak illustrates the devastating impact the MCF virus can have on bison under the proper exposure conditions, the high threat posed by adolescent lambs to susceptible species, the significantly greater susceptibility of bison than beef cattle to MCF, and the lack of horizontal transmission from clinically affected bison to herd-mates.

Last Modified: 9/1/2014
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