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

1

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

2

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

3

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

4

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