Tissue samples were removed at necropsy from five American bison (Bison bison) with clinical signs of a disease resembling malignant catarrhal fever (MCF). Using cell associated virus techniques, attempts were made to isolate viruses from these tissues by culturing them directly or by co-culture with bovine fetal cells. Among the viruses isolated was one which was syncytiogenic and multiplied in bovine fetal spleen cells and remained highly cell-associated. The presence of reverse transcriptase activity indicated that it was a retrovirus. Also, it had antigenic cross activity with bovine syncytial virus, but not with bovine leukemia or bovine maedi-like retroviruses. We do not attribute a direct causative role of this retrovirus to MCF, but indirect relationships are possible.

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Author notes


Department of Veterinary Microbiology and Parasitology, School Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana 70803, USA


Department of Veterinary Science, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge, Louisiana 70803, USA


Department of Microbiology and Environmental Health, Colorado State University, Fort Collins, Colorado 80523, USA


Veterinary Diagnostic Laboratory, Colorado State University, Fort Collins, Colorado 80523, USA