Acute Colitis and Diarrhoea
Learn what the condition is, how it may be detected early, how it is treated or managed, and which breeds or species are linked to it.
Condition snapshot
A concise guide to the condition’s pattern, detection, management and urgency.
This snapshot is a general guide, not a diagnosis or treatment plan. New, severe or worsening signs require veterinary assessment.
About the condition
Acute colitis is sudden inflammation and disruption of the large intestine, usually producing profuse diarrhoea and rapid loss of water, electrolytes and protein. Potential causes include Salmonella, Clostridioides difficile, Clostridium perfringens, equine coronavirus, cyathostomin larval emergence, antimicrobial-associated disruption and other inflammatory or toxic processes. In many adult horses a definitive cause is not identified, but supportive treatment can still be lifesaving.
The illness may begin with fever, dullness, loss of appetite and colic before diarrhoea appears. Feces can become watery and frequent, and an adult horse may lose an enormous proportion of extracellular fluid within a day. Heart rate rises, gums become dry or congested, limbs may become cold and urine production falls as circulation fails. Damage to the colon allows absorption of bacterial toxins and sometimes bacteria, leading to endotoxaemia, sepsis and coagulation abnormalities. Protein loss may cause dependent oedema.
Laminitis is a major secondary risk and can develop even while the intestinal signs are being treated. Other complications include kidney injury, thrombophlebitis, ileus and marked weight loss. Diarrhoea may also be infectious and transmissible, so a new acute case should initially be managed with separation and hygiene precautions until important contagious causes are assessed.
Acute diarrhoea differs from the soft manure associated with excitement, diet change or chronic hindgut dysfunction. Duration, systemic illness and hydration determine urgency. Foals have additional infectious and nutritional differentials and can deteriorate particularly quickly. Prognosis ranges from favourable in a mild self-limiting episode to guarded in horses with severe shock, profound neutropenia, persistent protein loss or laminitis.
Adult horses can lose enormous volumes of fluid and protein through an inflamed colon before outward dehydration appears dramatic. Endotoxin crossing the damaged bowel wall can impair circulation and trigger laminitis. Because antimicrobial-associated colitis may begin after treatment has stopped, the medication history must include the preceding several weeks rather than only drugs given that day.
Screening & Early Detection
Owners should seek veterinary assessment promptly when watery diarrhoea is accompanied by fever, depression, colic, reduced drinking or appetite. Useful history includes recent transport, hospitalisation, surgery, feed change, deworming, antimicrobial or anti-inflammatory medication, contact with diarrhoeic horses and whether other animals or people are ill. The horse should be separated, with dedicated equipment and careful hand hygiene, while the cause is investigated.
Assessment includes heart rate, temperature, gum colour, hydration, abdominal sounds, limb temperature and digital pulses. Serial blood tests monitor packed cell volume, total protein, white cells, electrolytes, kidney function, acid-base status, lactate and inflammatory markers. Fecal PCR or culture may test for infectious agents, but timing, intermittent shedding and laboratory method affect sensitivity. Multiple samples can be necessary for Salmonella. Ultrasound and abdominal-fluid analysis help evaluate colon thickness, motility and competing surgical disease.
Urine output, fluid losses, body weight and laboratory trends guide treatment intensity. Frequent hoof examination is needed for early laminitis detection. Stablemates should have temperatures and manure monitored according to the suspected cause, but a negative first fecal panel does not automatically justify ending isolation.
Treatment & Management
Treatment centres on replacing continuing fluid and electrolyte losses and protecting circulation. Severely affected horses require large volumes of carefully monitored intravenous crystalloid fluids; plasma or synthetic colloid support may be considered when protein loss is critical. Electrolyte, glucose and acid-base abnormalities are corrected from measured results. Analgesia and anti-endotoxin treatment are selected cautiously because dehydrated horses are vulnerable to kidney and gastrointestinal adverse effects.
Antimicrobials are not automatically beneficial for every adult with colitis and can further disrupt intestinal flora. They are reserved for documented or strongly suspected sepsis, neutropenia with systemic compromise, selected infectious diagnoses or other veterinary indications. Nutritional support is introduced according to intestinal function, appetite and severity rather than withholding forage indefinitely. Skin and tail care reduces scalding from frequent feces.
Laminitis prevention includes deep bedding, hoof support where indicated, cryotherapy in suitable high-risk cases and repeated digital-pulse assessment. Biosecurity requires dedicated clothing and equipment, controlled manure disposal, cleaning before disinfection and laboratory-informed release from isolation. Fluid balance and blood values may need review several times daily until stable. Prognosis improves when shock is corrected early; persistent fever, worsening neutropenia, kidney injury, severe hypoproteinaemia or laminitis indicates a more guarded course.
Breeds or species affected
Akhal-Teke
Open horse breed description, care requirements and conditions
Anglo-Arabian
Open horse breed description, care requirements and conditions
Arabian
Open horse breed description, care requirements and conditions
Barb
Open horse breed description, care requirements and conditions
Caspian
Open horse breed description, care requirements and conditions
Kathiawari
Open horse breed description, care requirements and conditions
Marwari
Open horse breed description, care requirements and conditions
Shagya Arabian
Open horse breed description, care requirements and conditions
Thoroughbred
Open horse breed description, care requirements and conditions
American Quarter Horse
Open horse breed description, care requirements and conditions
American Paint Horse
Open horse breed description, care requirements and conditions
Appaloosa
Open horse breed description, care requirements and conditions
Australian Stock Horse
Open horse breed description, care requirements and conditions
Brumby
Open horse breed description, care requirements and conditions
Waler
Open horse breed description, care requirements and conditions
Morgan
Open horse breed description, care requirements and conditions
Standardbred
Open horse breed description, care requirements and conditions
American Saddlebred
Open horse breed description, care requirements and conditions
Tennessee Walking Horse
Open horse breed description, care requirements and conditions
Missouri Fox Trotter
Open horse breed description, care requirements and conditions
Rocky Mountain Horse
Open horse breed description, care requirements and conditions
Peruvian Paso
Open horse breed description, care requirements and conditions
Criollo
Open horse breed description, care requirements and conditions
Mustang
Open horse breed description, care requirements and conditions
Canadian Horse
Open horse breed description, care requirements and conditions
Andalusian
Open horse breed description, care requirements and conditions
Lusitano
Open horse breed description, care requirements and conditions
Lipizzaner
Open horse breed description, care requirements and conditions
Friesian
Open horse breed description, care requirements and conditions
Dutch Warmblood
Open horse breed description, care requirements and conditions
Hanoverian
Open horse breed description, care requirements and conditions
Holsteiner
Open horse breed description, care requirements and conditions
Oldenburg
Open horse breed description, care requirements and conditions
Westphalian
Open horse breed description, care requirements and conditions
Trakehner
Open horse breed description, care requirements and conditions
Selle Français
Open horse breed description, care requirements and conditions
Belgian Warmblood
Open horse breed description, care requirements and conditions
Danish Warmblood
Open horse breed description, care requirements and conditions
Swedish Warmblood
Open horse breed description, care requirements and conditions
Swiss Warmblood
Open horse breed description, care requirements and conditions
Australian Warmblood
Open horse breed description, care requirements and conditions
Irish Sport Horse
Open horse breed description, care requirements and conditions
Cleveland Bay
Open horse breed description, care requirements and conditions
Württemberger
Open horse breed description, care requirements and conditions
Zangersheide
Open horse breed description, care requirements and conditions
Knabstrupper
Open horse breed description, care requirements and conditions
Orlov Trotter
Open horse breed description, care requirements and conditions
Camargue
Open horse breed description, care requirements and conditions
Icelandic Horse
Open horse breed description, care requirements and conditions
Pony of the Americas
Open horse breed description, care requirements and conditions
Quarter Pony
Open horse breed description, care requirements and conditions
Miniature Horse
Open horse breed description, care requirements and conditions
Clydesdale
Open horse breed description, care requirements and conditions
Shire
Open horse breed description, care requirements and conditions
Percheron
Open horse breed description, care requirements and conditions
Belgian Draft
Open horse breed description, care requirements and conditions
Suffolk Punch
Open horse breed description, care requirements and conditions
American Cream Draft
Open horse breed description, care requirements and conditions
Ardennes
Open horse breed description, care requirements and conditions
Breton
Open horse breed description, care requirements and conditions
Boulonnais
Open horse breed description, care requirements and conditions
Comtois
Open horse breed description, care requirements and conditions
Dutch Draft
Open horse breed description, care requirements and conditions
North Swedish Horse
Open horse breed description, care requirements and conditions
Norwegian Fjord
Open horse breed description, care requirements and conditions
Haflinger
Open horse breed description, care requirements and conditions
Gypsy Cob
Open horse breed description, care requirements and conditions
Irish Draught
Open horse breed description, care requirements and conditions
Welsh Pony and Cob
Open horse breed description, care requirements and conditions
Connemara Pony
Open horse breed description, care requirements and conditions
New Forest Pony
Open horse breed description, care requirements and conditions
Dartmoor Pony
Open horse breed description, care requirements and conditions
Exmoor Pony
Open horse breed description, care requirements and conditions
Shetland Pony
Open horse breed description, care requirements and conditions
Highland Pony
Open horse breed description, care requirements and conditions
Fell Pony
Open horse breed description, care requirements and conditions
Dales Pony
Open horse breed description, care requirements and conditions
Australian Pony
Open horse breed description, care requirements and conditions
Finnhorse
Open horse breed description, care requirements and conditions
Black Forest Horse
Open horse breed description, care requirements and conditions