Abstract
Fatal necrotic enteritis was observed in mice 24-52 days old in the RFM/Ms breeding colony maintained in a clean conventional condition in the National Institute of Radiological Sciences. Gross lesions included hyperaemia, petechiae, erosion and the occasional formation of pseudomembranes in the mucosa of the ileum and caecum. Histologically, there was necrotic enteritis with numerous Gram-positive bacilli-forming spores but no inflammatory cell reaction. Non-type-A Clostridium perfringens was isolated from the intestinal contents. This disease cleared after the addition of chlortetracycline hydrochloride (11 mg/I) to the drinking water.