Necrotic enteritis of unknown aetiology in young beef calves at pasture.

An enteric disease has occurred for four consecutive years (1989 to 1992) in a spring-calving beef suckler herd in east central Scotland affecting seven- to 12-week-old beef calves. The affected animals remained pyrexic (40 to 42 degrees C) with an acute enteritis which progressed in some cases to severe mucohaemorrhagic colitis. Despite intensive antibiotic and fluid therapy 25 per cent of the affected calves died after five to 10 days of illness. Post mortem examination revealed ulceration and necrosis of the mucosa of the abomasum and small and large intestine. Haematological examinations revealed a severe, non-regenerative neutropenia. Histopathological examination of gut and associated lymphoid tissue revealed lesions similar to those described in bovine viral diarrhoea/mucosal disease (BVD/MD) infection but detailed investigations failed to reveal evidence of active BVD virus infection in the herd. No aetiological agent has been found in association with this disease, for which the term necrotic enteritis is proposed.