EFFICACY OF AN OUTER-MEMBRANE COMPLEX HAEMOPHILUS-SOMNUS BACTERIN IN PREVENTING SYMPTOMS FOLLOWING HAEMOPHILUS-SOMNUS CHALLENGE

Twenty-five calves susceptible to Haemophilus somnus were divided into three groups. Two groups vaccinated with killed virus and one group w as vaccinated with a commercially available whole cell H. somnus bacte rin. The outer membrane complex (OMC) bacterin protected the calves fr om severe disease following H. somnus challenge. The commercial whole cell H somnus bacterin reduced lung lesions by 15.7% compared to the c ontrols. In this study, an extracted OMC H. somnus bacterin stimulated sufficient immunity to significantly reduce clinical disease symptoms and lung lesions following intratracheal challenge with virulent H. s omnus.