Vaccination of neonatal calves with a modified-live Mycoplasma (Mycoplasmopsis) bovis vaccine confers protection and enhances immunity

Objective: To evaluate the efficacy of a modified-live Mycoplasmopsis bovis vaccine administered to 1-week-old calves against virulent M bovis challenge and the immunological response of calves after revaccination. Methods: 2 studies were conducted using seronegative calves. In study 1, 85 calves received 2 SC doses of either vaccine or placebo 21 days apart and were challenged with virulent M bovis on days 32 to 34. Clinical signs, fever, and lung lesions were monitored. In study 2, 20 calves were assigned to control or vaccine groups. Calves received SC doses on days 0 and 21 and a revaccination on day 119 with their respective treatments. Serological responses were assessed. Results: In study 1, vaccinated calves showed significantly (P < .05) reduced lung lesions (5% vs 19% of total lung with lesions), shorter duration of clinical signs (1.3 vs 5.7 days), and fewer febrile days (2.9 vs 9.3) than controls. Antibody titers were higher at challenge and after challenge in vaccinates. Study 2 confirmed a similar response profile after 2 doses of M bovis vaccine and robust serological response after revaccination on day 119. Conclusions: The modified-live M bovis vaccine induced immunity against virulent M bovis challenge, with a reduction of lung lesions and clinical signs. A 2-dose regimen with a day 119 revaccination elicited a strong anamnestic response. Clinical Relevance: This vaccine can be introduced into bovine respiratory disease management in the natural setting to assess its impact on production by reducing the impact of M bovis.