An Epizootic of Malignant Catarrhal Fever in Feedlot Cattle

SUMMARY A remarkable epizootic of malignant catarrhal fever (mcf) occurred in cattle in Colorado during the winter of 1971-1972. In one group of 231 cattle, 87 (37%) died within 68 days. Twenty-three of the cattle (26.4% of those that died) died following a recognizable disease course of 1 to 2 days, with as many as 5 cattle sick in a single day; 43 of the cattle (49% of those that died) died within a 21-day period. The sickness was characterized by panophthalmitis, diarrhea, leukopenia, fever, and 100% mortality of visibly ill cattle. Postmortem lesions, typical of those associated with necrotizing vasculitis, consisted of hemorrhage, edema, ulcers, and necrosis in affected tissues.