Submitted to: Meeting Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 6/1/2005
Publication Date: 11/2/2005
Citation: Li, H., Taus, N.S., Jones, C., Murphy, B., O'Toole, D., Evermann, J.F., Crawford, T.B. Malignant catarrhal fever: a serious disease for american bison. November, 2005, 48th Annual Meeting of American Association of Laboratory Diagnosticians, Hershey, PA. P.118 Interpretive Summary:
Technical Abstract: This report describes two MCF outbreaks, indicative of the devastating impact this disease can have on American bison. The first MCF outbreak occurred in early 2002 on a Colorado bison ranch. A total of 62 (4.8%) out of 1288 bison developed clinical MCF between December of 2001 and May of 2002. No MCF case was reported on the ranch prior to exposure to sheep (n = 20,000) in a newly built sheep feedlot about 1 to 3 miles away from the exposed bison. The percentage of MCF cases appears to be correlated with the distances of exposed bison: 18.4% (43/234) for 1 mile; 6.1% (18/293) for 2 miles, and 0.4% (1/234) for 3 miles of distance, respectively. The second MCF outbreak occurred in a bison feedlot in southern Idaho and resulted in a 51.2 % (n = 825) mortality rate among bison which had been exposed to 7 month old sheep (n = 1400) for 20 days at a short distance. Peak losses in this outbreak 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. These outbreaks illustrate: 1) MCF has a devastating impact on bison under proper exposure conditions; 2) Adolescent sheep between 6 to 9 months of age pose a high threat to bison; 3) MCF can occur over a significant distance of exposure; 4) MCF-susceptibility is significantly greater in bison than in cattle; 5) The bison with clinical MCF do not pose any risk of horizontal transmission of the virus to herd-mates.