Acute febrile diarrhoea in horses: 86 cases (1986–1991)

SUMMARY: Eighty-six horses presented for examination at the Rural Veterinary Centre between January 1986 to December 1991 with acute diarrhoea. The average age of affected horses was 3.2 ± 0.2 years (mean ± SE), with 69% three years or younger. Sixty-one horses were male (36 stallions, 25 geldings) and 83 horses were Thoroughbreds (47) or Standardbreds (36). Sixty-six horses were undergoing routine training at the time of onset of diarrhoea. Eight horses were afflicted with a non-specific illness within one to five days before the onset of diarrhoea, whereas eight horses developed diarrhoea during or within 48 h of discontinuation of antimicrobial therapy. Three horses developed the diarrhoea within 24 h of road transportation. Clinically, the disorder was characterised by a fever, sudden onset of profuse diarrhoea, clinical evidence of dehydration (estimated to be 5 to 12% of body weight at the time of admission) and shock. Degenerative leucopaenia, hyponatraemia, hypochloraemia, hyperkalaemia, hyperglycaemia and azotaemia were characteristic laboratory findings. Laminitis was a sequel in about 30% of cases. The cause of diarrhoea remained undetermined in most cases. Salmonellas were isolated from faecal or tissue samples in only two cases. Similarly, there was no evidence of seroconversion to Erhlichia risticii in 17 cases. Sixty-two of the horses survived the acute phase of the disease in response to supportive care. In horses that did not survive, necropsies were performed and revealed sanguineous or turbid peritoneal fluid. The colonic and caecal walls were oedematous and thickened with serosal congestion and discolouration of these organs evident grossly. Histopathological examination of the caecum and colon revealed diffuse congestion, oedema, inflammatory reactions and submucosal vascular thrombosis with varying degrees of mucosal devitalisation. Most cases presented in this series represent a distinct syndrome of diarrhoea characterised by acute diarrhoea predominantly affecting young horses in training with concomitant signs of fever and toxaemia.