Effect of anti-prostaglandin therapy in experimental parainfluenza type 3 pneumonia in weaned, conventional calves.

An acute pneumonia was induced experimentally in 10, 10- to 12-week-old conventional calves by administration into the upper airways of a pathogenic strain of parainfluenza type 3 (PI3) virus. The experimental calves had been selected on the basis of freedom from clinical evidence of respiratory and other diseases, freedom from current infection by PI3 virus as judged by repeated nasopharyngeal swabbing and freedom from earlier PI3 virus infection as judged by their lack of significant levels of serum antibody to that virus. The infection procedure was deemed to have been successful in that infection was established with subsequent seroconversion, clinical signs of a febrile pneumonia arose soon after the administration of virus, histopathological changes characteristic of PI3 pneumonia developed and the presence of PI3 virus antigen was demonstrated by immunofluorescence in association with those lesions. Treatment of five of the pneumonic calves was carried out on days 1, 2 and 3 of the trial using the anti-prostaglandin compound flunixin meglumine and that treatment appeared to be of benefit in that in the test calves there was a prompt cessation of coughing with fewer fevers and lower respiratory rates as compared with the untreated controls. The drug did not appear to influence PI3 infection rates but its administration was associated with a marked reduction in the extent of pulmonary consolidation, probably as the result of its known ability to limit the acute inflammatory response.