The experimental production of pneumonia in calves by intranasal inoculation of parainfluenza type III virus.

Thirteen colostrum deprived calves were inoculated with a low passage field strain of parainfluenza type III (PI 3) virus. Virus was administered by the intranasal route and the calves were experimentally infected twice daily for four consecutive days. Clinical signs of respiratory disease were noted and pneumonia was present in 12 animals at necropsy. PI 3 virus was isolated from the lung lesions and no other respiratory pathogens could be demonstrated. The pneumonic lesions grossly, histologically and in their distribution resembled those encountered in naturally occurring outbreaks of indoor calf pneumonia.