Effects of infection with parainfluenza-3 virus and infectious bovine rhinotracheitis virus on neutrophil functions in calves.

Calves were challenge exposed in separate experiments with parainfluenza-3 (PI-3) virus or infectious bovine rhinotracheitis (IBR) virus. Blood neutrophils were assayed for functional activity every other day for at least 3 weeks by random migration, Staphylococcus aureus ingestion, antibody-dependent cell-mediated cytotoxicity, cytochrome-c reduction, iodination, and native chemiluminescence. Exposure to PI-3 virus resulted in a brief febrile response and no other clinical signs. Alterations in total or differential WBC counts were not detected. Chemiluminescence and iodination activities were reduced from activities before exposure. Exposure to IBR virus resulted in mild clinical signs and a febrile response of several days' duration. Total WBC and mononuclear cell counts were reduced. Random migration was reduced, whereas S aureus ingestion was enhanced. We concluded that infection of calves with IBR virus and PI-3 virus might directly or indirectly result in alterations of neutrophil function. The functional alterations apparently are different for each virus. These virus-induced alterations in neutrophil function might predispose calves to secondary bacterial pneumonia.