Colitis X

Description

Colitis X (so-called due to its unknown aetiology) is a peracute and highly fatal disease of horses. Is characterised by severe colitis, sudden watery diarrhoea and death within 24 hours. A number of possible underlying causes have been described, including drug or parasite hypersensitivity, stress and transport. Clostridium perfringens Type A has been hypothesised to be a cause of Colitis x, and high-protein, low-cellulose diets or antimicrobial treatment may predispose to Clostridial overgrowth. Recently a link has been demonstrated with the current human epidemic strain of Clostridum difficile (ribotype 027/toxinotype III) clostridial enterocolitis.

Signalment

Colitis X affects adult horses, usually between one and ten years old.

Clinical Signs

• Abdominal pain
• Acute onset watery to haemorrhagic diarrhoea
• Tachycardia (Heart rate often greater than 100bpm)
• Dehydration
• Signs relating to hypovolaemic or endotoxic shock, e.g. congested mucous membranes, prolonged capillary refill time, cold extremities.
• Dilated pupils
• Collapse
• Body temperature may vary from pyrexic to subnormal
• Bowel sounds may be absent

The clinical signs are similar to those described for other forms of acute- peracute colitis, particularly acute salmonellosis. Rectal examination may often be normal. Other diagnoses that must be considered include grass sickness, acute small intestinal obstructions and intestinal thromboembolic infarctions.

Diagnosis and Pathology

Colitis x is a diagnosis made by exclusion. The above examination findings may be reported combined with an increased plasma urea concentration (greater than 10 mmol/l), increased PCV, leucopaenia, metabolic acidosis, hypokalaemia and hyponatraemia.

Diagnosis is often made post-mortem, where a hyperaemic or oedematous caecum and ventral colon may be seen with necrosis of the intestinal in the later stages of the disease. Numerous gram negative bacteria may be identified in the mucosa and submucosa. The intestinal tract may be filled with a foul smelling and watery content. Macroscopic and microscopic findings include signs of disseminated intravascular coagulation and large numbers of bacteria in the devitalized parts of the intestine. A green diphtheritic

Treatment

Treatment is often unsuccessful and affected horses often require euthanasia. Aggressive fluid therapy and electrolyte replacement must be initiated, usually using a wide bore catheter. Pain is often severe and potent analgesics such as flunixin meglumine are required. The administration of sodium benzyl penicillin may be beneficial as Clostridium spp are sensitive to this type of antibiotic.

Prognosis

The prognosis is usually poor, with a mortality rate approaching 90-100%. This may be lower for horses receiving intensive treatment.

References

• Glenn Songer, J., Trinh, H.T., Dial, S.M., Brazier, J.S., Glock, R.D. (2009) Equine colitis X associated with infection by Clostridium difficile NAP1/027 Journal of Veterinary Diagnostic Investigation 21:377–380

• Diakakis, N. (2008) Equine colitis X Journal of the Hellenic Veterinary Medical Society (Hellenic Veterinary Medical Society) 59:23–28(6)

• Schiefer H.B. (1981). Equine colitis "X", still an enigma? The Canadian Veterinary Journal. La Revue Vétérinaire Canadienne 22 (5):162–5

• White, N.A., Edwards, G.B. (1999) Handbook of Equine Colic Reed Educational and Professional Publishing Ltd

• Knottenbelt, D.C. A Handbook of Equine Medicine for Final Year Students University of Liverpool

• Rose, R.J. and Hodgson, D.R. Manual of Equine Practice Saunders Elsevier

• Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial