Effect of vaccination on the potentiation of porcine reproductive and respiratory syndrome virus (PRRSV)-induced pneumonia by Mycoplasma hyopneumoniae

Porcine reproductive and respiratory syndrome virus (PRRSV) and Mycoplasma hyopneumoniae are frequently isolated pathogens from pigs with respiratory disease. A previous study conducted in our laboratory found that infection with M. hyopneumoniae increased the duration and severity of respiratory di sease induced by PRRSV. The purpose of this experiment was to determine whe ther vaccination against M. hyopueumoniae and/or PRRSV decreased the enhanc ement of PRRSV-induced pneumonia. Both M. hyopneumoniae bacterin and PRRSV vaccine decreased the severity of clinical respiratory disease. Infection o r vaccination with PRRSV appeared to decrease the efficacy of the M. hyopne umoniae bacterin. Vaccination with nl. hyopneumoniae bacterin decreased the potentiation of PRRSV-induced pneumonia observed in the dual infected pigs . However, PRRSV vaccination in combination with M. hyopneumoniae bacterin eliminated this benefit and the amount of pneumonia induced by PRRSV increa sed. PRRSV vaccine alone did not decrease the potentiation of PRRSV pneumon ia by hi. hyopneumoniae. (C) 2000 Elsevier Science Ltd. All rights reserved .