Isolation of parainfluenza virus from the lungs and nasal passages of sheep showing respiratory disease

Isolations of parainfluenza 3 (PI3) virus were made from pneumonic lung tissue of 2 lambs and from the nasal passages of a further 4 lambs in a group of 10 involved in an outbreak of respiratory disease. Pasteurella haemolytica was isolated from the lungs of each of the 4 lambs which were killed for post-mortem examination. On histological examination changes of both an acute exudative and proliferative nature were observed in each lung. In one lung, from which virus was isolated, acidophilic cytoplasmic inclusions were present in bronchiolar epithelial cells. No PI3 virus antibodies were detected in serum samples collected prior to the onset of respiratory disease in the group. One of the lambs which was killed and 5 of the 6 which were not slaughtered subsequently developed antibodies against PI3 virus. Each lamb first showed antibody response in serum samples collected at the time of, or immediately following, respiratory disease or a severe febrile illness. The possible relationship of PI3 virus infection to the clinical and pathological findings is discussed.