Study on the etiologic role of bovine respiratory syncytial virus in pneumonia of dairy calves.

Bovine respiratory syncytial virus (BRSV) was the viral agent most commonly identified in 14 epizootics of pneumonia in dairy calves. A microtiter serum-virus neutralization test proved to be the best means of identifying involvement of BRSV; seroconversion (fourfold or greater rise in titer) was demonstrated in 10 of the 14 epizootics. Only limited involvement of bovine viral diarrhea virus, infectious bovine rhinotracheitis virus, parainfluenza 3 virus, and bovine adenovirus type 3 was recognized. Pasteurella multocida was isolated in 12 of 14 epizootics, and Pasteurella haemolytica in 4 of 14 epizootics. Mycoplasmal and ureaplasmal agents were isolated in all 14 epizootics.