Colitis in Horses: Diarrhoea, Emergency Signs and Treatment
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By Dr Duncan Houston
Sudden watery diarrhoea in an adult horse deserves an urgent call. A horse can lose substantial fluid and develop serious circulatory problems before it looks dramatically unwell.
Colitis means inflammation of the colon. It is a description of where the problem is occurring, not one disease with one standard treatment.
Quick Answer
Acute colitis can cause diarrhoea, colic, fever and rapid dehydration, with risks including shock and laminitis. Contact your equine vet promptly for new watery diarrhoea and immediately if the horse is painful, weak or dull. Isolate the horse and avoid sharing equipment until an infectious cause has been assessed.
Why can colitis become serious so quickly?
The large intestine normally helps manage water and electrolyte balance. Inflammation disrupts that function and may allow protein loss and bacterial products to affect the circulation. Treatment is often needed before a specific cause has been identified.
The veterinary review of acute adult-horse diarrhoea describes its potentially life-threatening nature and the importance of supportive treatment. There is no safe advice to wait several days in a horse with acute watery diarrhoea and systemic signs.
What causes it?
Possible causes include Salmonella, clostridial disease, regionally relevant infections, parasites, antibiotic-associated disruption and medication injury. Sand accumulation and some dietary or inflammatory disorders may also contribute.
Non-steroidal anti-inflammatory drugs can cause right dorsal colitis, particularly when dosing or hydration is inappropriate. Give your vet a complete medication history, including products administered by different carers. Two different brand names may still represent overlapping drugs.
The MSD infectious-diarrhoea overview notes that a precise cause is not always found. An unrevealing first test does not make the horse’s illness less real.
How urgent are the signs?
| Finding | Action |
|---|---|
| Persistent soft manure, otherwise bright and eating | Discuss promptly with your vet and monitor for change. |
| New watery diarrhoea, even while still standing and alert | Call your vet now for triage and examination planning. |
| Diarrhoea with colic, fever, weakness, abnormal gums or rapid breathing | Emergency veterinary care. |
What else needs consideration?
Free faecal water with otherwise formed droppings is different from profuse diarrhoea, although persistent changes still need assessment. Surgical intestinal disease can cause colic and circulatory compromise without much diarrhoea. Foals have different infectious and nutritional considerations from adults.
Your vet assesses hydration, circulation, abdominal findings and temperature. Blood tests, faecal testing, ultrasound and other investigations are selected according to the case. Repeated samples may be needed for intermittently shed organisms.
When is this an emergency?
Call immediately for severe or persistent pain, weakness, collapse, markedly abnormal gums or diarrhoea with systemic illness. Hospital treatment may be needed. Notify the receiving clinic before travelling so it can prepare isolation and safe admission.
What should you do right now?
- Stop work and call the vet with onset, manure changes, appetite, pain and medication history.
- Separate the horse and dedicate buckets, forks and other equipment.
- Use gloves, wash hands and prevent contaminated boots or manure reaching other horses.
- Offer clean water if the horse is alert and can swallow, but do not force drenches.
- Ask about feeding and medication while waiting. Do not add human antidiarrhoeal drugs or leftover antibiotics.
Keep a record of diarrhoea frequency, drinking, urine output and behaviour. Take temperature only if safe. People can acquire some intestinal pathogens from horses, so keep children and vulnerable people away from contaminated areas.
What does treatment involve?
Veterinary care may include substantial intravenous fluids, correction of electrolytes, pain management, nutritional support and measures against complications. Selected horses need plasma or other intensive support. Treatment is tailored to circulation and test results.
Antibiotics are not automatically beneficial in adult colitis. The MSD salmonellosis reference explains why antimicrobial decisions depend on systemic risk and the individual case. A bacterial name on a test does not justify a universal prescription.
Common mistakes
- Waiting because the horse is still eating a little.
- Giving extra anti-inflammatory medication for repeated colic.
- Sharing stable equipment before infection is excluded.
- Using probiotics as a substitute for fluid therapy.
- Transporting without warning the receiving clinic.
Prevention and recovery
Make feed changes gradually, use medications exactly as prescribed and maintain appropriate parasite and sand-risk management. During recovery, follow the feeding and exercise plan and ask how long isolation is needed. Returning manure consistency does not automatically mean circulation, protein levels and infection risk have normalised.
Frequently asked questions
Is all colitis contagious?
No, but use isolation precautions until your vet assesses the cause.
Does colitis always cause diarrhoea?
No. Some forms can initially present with colic or protein loss.
Can probiotics cure it?
No. They cannot replace urgent assessment and appropriate supportive care.
Will my horse recover?
Many do with treatment, but outcome depends on severity, cause and complications.
With acute colitis, early assessment and fluid support can make a substantial difference. Call before deterioration becomes obvious.
For help understanding your horse’s care and preparing questions for your veterinarian, visit ASK A VET™. Urgent signs need an equine veterinarian in person.
