Severe systemic histophilosis in a dairy sheep flock in France

A severe outbreak of histophilosis occurred in a dairy sheep flock in southern France, affecting replacement ewe lambs, rams and one adult ewe aged 10–24 months. Over a 3‐week period, 29 animals developed acute lameness, respiratory distress or neurological signs, and five died despite antimicrobial treatment. Two postmortem examinations revealed fibrinous pleuropneumonia and pericarditis. Histophilus somni was isolated in pure culture from lung tissue and synovial fluid of two sheep. The source of infection could not be identified. This report highlights the pathogenic potential of H. somni in sheep and the likelihood that ovine histophilosis is underdiagnosed in European flocks.