Reduction of mycoplasmal lesions and clinical signs by vaccination against Mycoplasma hyorhinis

Porcine mycoplasmal pneumonia is a significant disease problem in the swine industry. The causative agents include Mycoplasma hyopneumoniae and Mycoplasma hyorhinis. M. hyopneumoniae is the major pathogen contributing to the porcine respiratory disease complex, but is difficult to isolate from the respiratory tract and tonsils, whereas M. hyorhinis is not. Although M. hyorhinis is commonly detected in the lungs, the role of M. hyorhinis as a cause of pneumonia remains unclear. Current vaccines for porcine mycoplasmal pneumonia only include M. hyopneumoniae, not M. hyorhinis. M. hyopneumoniae vaccines are widely used, but disease still occurs because of poor vaccine efficacy and possibly the presence of M. hyorhinis. In this study, an inactivated vaccine containing a mixture of M. hyorhinis and M. hyopneumoniae was generated and evaluated for safety, immunogenicity, and protective efficacy against challenge with M. hyorhinis in pigs. The inactivated vaccine induced an antibody response and reduced pneumonic lesions in the lungs and tracheas compared with the non-vaccinated group.