In order to determine whether elk (Cervus elaphus) could be infected with and shed bovine viral diarrhea virus (BVDV) and to determine whether BVDV could cause disease in elk, two groups of five yearling elk each and two control cattle were experimentally inoculated intranasally with type 1 Singer strain or a virulent type 2 isolate of BVDV, strain 24515. Virulence of the type 2 isolate was confirmed by inoculation of a control bovine cow which developed diarrhea, dehydration, severe thrombocytopenia, hemorrhages, and enteritis with intestinal necrosis. None of the elk inoculated with type 1 or type 2 BVDV developed clinical signs of illness. However, all elk became infected as demonstrated by viremia, nasal shedding, and/or seroconversion. One uninoculated, in-contact elk contracted type 1 BVDV and seroconverted. Thus, although BVDV does not appear capable of producing disease in nonpregnant elk, the species is susceptible to infection and can shed and transmit BVDV.

In late spring of 1986, 10 of 23 Dall's sheep (Ovis dalli dalli) at the Metropolitan Toronto Zoo were moved to a new exhibit, where all developed severe respiratory signs refractory to anthelmintic and antibiotic therapy. In July, two animals died with chronic active bronch-pneumonia, and a third was euthanized because of pneumonia several months later. Bacteria were not isolated from the lungs of the first, steptococci and Pasteurella hemolytica were isolated from the other two, respectively; Mycoplasma ovipneumoniae was isolated from both. Pulmonary lesions in all three sheep were consistent with Mycoplasma sp. infection. Nasal swabs of the remaining animals yielded no consistent bacterial isolates; however, four of eight sheep were positive for M. ovipneumoniae. Viral cultures yielded an as yet unidentified herpesvirus. Sheep in the original and new herds had no serologic titers to parainfluenza-3, equine viral rhinopneumonitis, or infectious bovine rhinotracheitis, and had variable titers against bovine respiratory syncytial virus. No titers against M. ovipneumoniae were present in 13 sheep still in the original exhibit, but titers varied from 1:32 to 1:256 in eight pneumonic sheep. Sera taken from three sheep before or early in the outbreak were all negative for antibody to M. ovipneumoniae. Two of the affected Dall's sheep had been in contact with domestic sheep in the winter of 1985-1986, and M. ovipneumoniae was subsequently cultured from the domestic flock. Exposure to a new pathogen, and environmental and social stress in a new exhibit may have resulted in this severe disease in Dall's sheep.

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