Outbreak of botulism in commercial laying chickens

Abstract This case report describes a fatal botulism outbreak in a free‐range flock of commercial laying hens in Northern Ireland. Affected birds presented with dullness and an inability to stand or open their eyes. Postmortem examination revealed no significant gross abnormalities. This, along with the presenting clinical signs alerted veterinary investigators to test samples for botulism. Group III botulinum neurotoxins were detected by a monoclonal antibody‐based ELISA in a pooled serum sample and in one of the caecal samples. Gastrointestinal tract samples and environmental samples tested positive by ELISA for Group III botulinum neurotoxins following culture indicating the presence of Clostridium botulinum Group III spores. A diagnosis of botulism was confidently made. To the authors’ knowledge, this is the first reported case of botulism in layers as old as 72 weeks and the first time botulism in layers of any age has been reported in Northern Ireland.