Effects of Moraxella bovis vaccination schedules on experimentally induced infectious bovine keratoconjunctivitis

An oil-adjuvant Moraxella bovis bacterin was administered to weanling calves, using different vaccination schedules. Calves were given a booster vaccination after 3 weeks and were challenge exposed 2 weeks later with virulent M bovis recovered from calves with clinical infectious bovine keratoconjunctivitis (IBK). The effects of different routes of vaccination and homologous and heterologous challenge exposure on the incidence, severity, and duration of induced IBK was evaluated. All calves given a placebo developed clinical IBK. Calves vaccinated subcutaneously in the neck had the shortest duration of M bovis infection, the lowest incidence and the shortest duration of acute IBK, and the lowest disease severity score, compared with effects in calves given a placebo or vaccinated subconjunctivally. Calves challenge exposed with the homologous strain of M bovis had more infected eyes, more eyes with acute IBK, longer duration of infection, and a higher severity and duration disease score.