Other Names
- Equine IBD (Inflammatory Bowel Disease)
- Multisystemic Eosinophilic Epitheliotropic Disease (MEED)
- Equine Intestinal Granulomatosis
- Chronic Inflammatory Bowel Disease
What is Equine Granulomatous Enteritis?
Equine Granulomatous Enteritis (EGE) is a rare but serious inflammatory condition of the gastrointestinal tract in which the intestinal wall becomes infiltrated with inflammatory cells — principally macrophages forming characteristic granuloma clusters, and in some cases eosinophils and lymphocytes. The disease causes progressive thickening and dysfunction of the intestinal lining, impairing nutrient and protein absorption.
The condition belongs to a broader group of equine inflammatory bowel diseases, which also includes lymphocytic-plasmacytic enteritis and eosinophilic enteritis. EGE is characterised by the formation of discrete granulomas — collections of activated macrophages — within the gut wall. In its multisystemic form (MEED), similar inflammatory infiltrates may be found in the skin, lymph nodes, liver, and other organs, making it a complex systemic disease rather than a purely intestinal one.
EGE is difficult to treat and carries a guarded long-term prognosis, but early diagnosis and appropriate management can significantly extend quality of life.
Causes
The precise cause of EGE remains incompletely understood. Current evidence points towards a dysregulated immune response rather than a single infectious agent, though various triggers have been proposed:
- Abnormal immune response: An inappropriate inflammatory reaction to dietary antigens, microbial components, or intestinal bacteria is the leading hypothesis — analogous to Crohn’s disease in humans
- Dietary allergens: Hypersensitivity to specific feed components such as grain proteins or pasture fungi has been suggested in some cases
- Infectious agents: Mycobacterium species and other mycobacterial-type organisms have been implicated in some cases, given the granulomatous nature of the lesions
- Parasitic hypersensitivity: Chronic exposure to gastrointestinal parasites may trigger granulomatous responses in susceptible individuals
- Genetic predisposition: Certain breeds and individual horses may be genetically predisposed to dysregulated gut immunity
The disease does not appear to be contagious between horses. Standardbreds and Thoroughbreds are reportedly over-represented in case series, though any breed can be affected.
Symptoms and Signs
EGE is a progressive disease with gradual onset. Common signs include:
- Chronic weight loss despite a good appetite — horses continue eating but cannot absorb nutrients effectively
- Ventral oedema (fluid swelling along the underside of the belly, between the front legs, and around the sheath or udder) — caused by protein loss from the damaged intestinal lining
- Hypoproteinaemia — low blood protein, particularly low albumin
- Intermittent diarrhoea, sometimes alternating with normal faeces
- Lethargy and reduced exercise tolerance
- Poor coat condition and general unthriftiness
- In MEED cases: skin crusting, scaling, or exfoliation — particularly over the face, coronary bands, or distal limbs
- Peripheral lymph node enlargement (in multisystemic cases)
The combination of weight loss, ventral oedema, and chronic diarrhoea in a horse with reasonable appetite should prompt consideration of protein-losing enteropathy, of which EGE is a significant cause.
Diagnosis
Diagnosis requires a combination of clinical findings, blood work, and ultimately intestinal biopsy:
- Serum protein analysis: Low total protein and albumin are hallmark findings. Elevated globulins may also be present.
- Rectal biopsy: A relatively straightforward procedure that samples the rectum under sedation. Whilst not always representative of small intestinal disease, rectal biopsies showing granulomatous infiltration are highly supportive of the diagnosis.
- Intestinal biopsy via laparotomy: Full-thickness biopsy of the small intestine or jejunum is the gold standard for definitive diagnosis. It allows accurate characterisation of the inflammatory infiltrate type and guides treatment.
- Gastroscopy and duodenoscopy: May reveal abnormal mucosa in the stomach and proximal duodenum; biopsies can be obtained endoscopically in specialist centres.
- Abdominal ultrasound: May reveal thickened intestinal walls and enlarged mesenteric lymph nodes.
- Glucose absorption test: An indirect assessment of small intestinal function; impaired glucose absorption suggests malabsorption but is not specific for EGE.
- D-xylose absorption test: More specific measure of small intestinal absorptive capacity.
Differentiating EGE from other causes of protein-losing enteropathy such as lymphoma, right dorsal colitis, and cyathostominosis is essential as treatments differ significantly.
Treatment
Treatment aims to suppress the abnormal immune response and manage nutritional deficits:
- Corticosteroids: Dexamethasone or prednisolone are the mainstay of treatment, used to suppress the granulomatous inflammation. Initial doses are high, with gradual tapering over months as the horse responds. Long-term maintenance therapy is often required.
- Dietary modification: Elimination of suspected dietary antigens, particularly grain-based feeds. Feeding of easily digestible, high-quality hay or grass, with supplementation to compensate for malabsorption. High-protein feeds to address hypoproteinaemia.
- Nutritional support: Vitamin and mineral supplementation, particularly fat-soluble vitamins, is often necessary.
- Anthelmintic treatment: Strategic deworming to eliminate any parasitic contribution to the inflammatory burden.
- In MEED cases: Additional immunosuppression may be required to manage skin manifestations.
Response to treatment varies considerably. Some horses improve substantially on corticosteroids and dietary management; others remain refractory or relapse when medication is reduced.
Prevention
Given the incompletely understood aetiology, definitive prevention is not possible. Maintaining a consistent, high-quality diet, regular strategic parasite control, and minimising dietary changes that might trigger adverse gut responses are the most practical preventive measures for horses that may be predisposed.
Prognosis
The prognosis for EGE is guarded to poor in the long term. Many horses require lifelong corticosteroid therapy, and the risks of long-term steroid use (including laminitis) must be weighed against the benefits. Some horses achieve good-quality remission and return to reasonable use; others continue to decline despite treatment. Cases presenting with very low albumin, extensive lesions, or multisystemic involvement carry the most serious outlook. Owners should be prepared for long-term management and realistic expectations about athletic performance.
When to Call the Vet
Seek veterinary attention if your horse:
- Is losing weight despite a normal or increased appetite
- Develops swelling along the underside of the belly or limbs
- Has persistent or intermittent diarrhoea lasting more than a week
- Shows skin changes alongside gastrointestinal signs
- Is generally unthrifty and failing to respond to routine dietary management
Frequently Asked Questions
Is equine granulomatous enteritis the same as Crohn’s disease in horses?
The two conditions share significant similarities — both involve granulomatous inflammation of the gut wall driven by an abnormal immune response, and both are chronic and difficult to treat. However, EGE is a distinct veterinary diagnosis and the underlying genetic and immunological mechanisms differ. The analogy to Crohn’s disease is useful for understanding the nature of the condition but should not be taken as exact equivalence.
Can a horse with EGE return to work?
Some horses with EGE achieve sufficient remission to return to light or moderate work, particularly if they respond well to corticosteroids and dietary management. However, horses with advanced disease or poor protein status are unlikely to return to full athletic performance. Any return to work should be gradual and carefully monitored.
How is EGE different from lymphoma in horses?
Both conditions cause protein-losing enteropathy and weight loss in horses, and they can be impossible to distinguish clinically. Intestinal biopsy is essential to differentiate them — lymphoma shows neoplastic lymphocytic infiltration, while EGE shows granulomatous or eosinophilic inflammation. The distinction matters enormously for treatment and prognosis.
What diet is best for a horse with granulomatous enteritis?
Most horses benefit from a grain-free, highly digestible forage-based diet. Alfalfa (lucerne) hay is often recommended due to its higher protein and calorie density. Commercial feeds based on beet pulp and oil may also be useful. Dietary changes should be made gradually and monitored closely for response. See also: Equine Pharyngitis and hypoproteinaemia for related conditions that can complicate intestinal disease management.