A Preliminary Investigation on a Commercial Ovine Pasteurellosis Vaccine Using Clinical and Pathological Endpoints.

Introduction: In this study we aimed to provide preliminary evidence on the safety and efficacy of the currently used ovine pasteurellosis vaccine in Ethiopia using clinical and pathological endpoints. Methods: Twenty, conventionally reared, apparently healthy, seronegative male lambs, were randomly classified into two groups of 10 animals as "vaccinated-challenged" and "unvaccinated-challenged controls". The first group received 1 mL of the licensed Results: There were no safety issues recorded during the study. In terms of clinical signs, lambs developed fever, depression, mucoid bilateral oculonasal discharge, coughing and sneezing regardless of their vaccination status. Fisher's exact test between vaccination status and each clinical sign showed a statistically insignificant association ( Discussion and Conclusion: Collectively, the results suggested that the vaccine posed no safety concern and presumably lacks protective efficacy against local isolates. However, the study did not analyze antibody titer and their functionality using serum bactericidal assays. Further confirmatory studies could provide more evidence on the vaccine efficacy. Safety should further be assessed in a field setting involving a large number of animals to enable detection of rare vaccine adverse events.