Enteritis & Inflammatory Bowel Disease in Horses: Risk Factors, Treatment & Prevention

Enteritis is a serious condition in horses, characterized by inflammation of the intestinal tract. Enteritis can disrupt the digestive system and lead to symptoms such as diarrhea, colic, and weight loss.

This condition can affect horses of any age but is more common in younger horses, stressed horses, and those exposed to affected horses.

Enteritis can be caused by a variety of factors, including bacteria, toxins, viruses, and nutritional issues. Effective management is important for the horse’s recovery, though diagnosing the underlying cause can be challenging.

By learning about the symptoms, causes, and treatment options for enteritis in horses, caretakers and owners can ensure prompt medical intervention before the condition progresses.

Enteritis in Horses

Enteritis is defined as inflammation in the intestinal tract of the horse. Enteritis is an umbrella term that covers a variety of disorders, ranging from moderate discomfort to life-threatening colic. ^[1]

In affected horses, this condition interferes with the normal functions of the horse’s digestive system, leading to diarrhea and colic. A number of different syndromes can lead to equine enteritis.

As a generalized medical term, “enteritis” is applied in various ways. Sometimes, the term enteritis is used specifically to refer to inflammation in the small intestine, with the term colitis reserved for inflammation in the large intestine. In some medical literature, the term enterocolitis is used for general inflammation in any part of the intestinal tract. Other times, the term enteritis is used to describe general inflammation in any part of the intestinal tract.

In addition, some experts use the word “enteritis” interchangeably with “inflammatory bowel disease” (IBD), which is also a general term. In current practice, IBD is usually reserved for cases where an immune-mediated cause is suspected, but there is wide variance in the use of both terms.

For the purposes of this article, the term enteritis refers to general inflammation in any part of the intestinal tract unless otherwise stated.

Intestinal Anatomy

The horse’s digestive system is a long series of tubes and sacs. In general, two sections of the gastrointestinal tract are affected by enteritis: the small intestine and the large intestine (colon).

The small intestine is a long, winding tube in the foregut that runs from the stomach to the cecum. It is responsible for continuing the digestion of proteins, fats and some carbohydrates (starches and sugars) that started in the stomach. ^[2]

The large intestine is located in the hindgut and runs from the cecum to the rectum. It is responsible for digesting the structural carbohydrates that make up the majority of the horse’s nutrient intake. ^[3]

Inflammatory Response

Enteritis occurs when any section of the horse’s colon becomes inflamed. Inflammation is the body’s natural response to injury, infection, or other harmful stimuli. It is a complex process that involves various immune cells, signaling molecules, and changes in blood flow. ^[4]

Inflammation begins when the body detects harmful stimuli such as a pathogen (i.e. bacteria, viruses, or parasites), toxins, or physical damage from traumatic injury. When cells in the affected area detect injury or infection, they release signaling molecules called cytokines that recruit immune cells to the site. ^[5]

As the inflammatory response develops, blood vessels in the affected area dilate, increasing blood flow (vasodilation). Vasodilation helps bring more immune cells, nutrients, and oxygen to the affected area. ^[4][5]

During this process, the walls of the blood vessels become more permeable, allowing immune cells, proteins, and fluid to leak into the surrounding tissue. This leads to the swelling associated with inflammation. ^[4][5]

As immune cells arrive and start working at the site, they release more cytokines and other inflammatory mediators, amplifying the response. This signals other immune cells such as lymphocytes to help with more specific immune responses. ^[5]

Effects of Inflammation

During the inflammatory response, the horse may experience pain and loss of function in the affected area.

Pain is caused by the stimulation of nerve endings from various inflammatory mediators. ^[5] In cases of enteritis, pain signals originathing from the colon can lead to signs of colic in the affected horse.

Loss of function is caused by swelling and tissue damage, as well as pain itself. In the gut, this swelling and tissue damage disrupt normal digestive processes, gut motility, and fluid balance. This change in function leads to symptoms such as diarrhea.

Symptoms

The symptoms of enteritis in horses are variable and non-specific. This means that no one symptom shows up in every case of enteritis, and the signs of enteritis are also symptoms of other diseases. This, combined with the fact that enteritis often begins subtly and progresses slowly, makes early detection and confirmation of the underlying cause difficult. ^[6]

A main symptom of enteritis is pain in the horse’s abdomen, commonly known as colic. In cases of enteritis, colic may be intermittent, and is often mild to moderate. ^[7] Colic may improve with the administration of pain relief, but usually recurs once the medications wear off. ^[7]

The signs of colic include: ^{[8][9][10][11]}

• Lethargy
• Lack of appetite
• Decreased stomach noises
• Rapid breathing (tachypnea)
• Rapid heartbeat (tachycardia)
• Sweating
• Bloating
• Biting or staring at the flanks
• Adopting unusual body positions including stretching, dog-sitting, crouching, or lying on the back
• Restlessness including shifting weight, circling, pacing, biting, repositioning the body, or nibbling non-food items
• Lying down
• Rolling
• Teeth grinding
• Kicking at the abdomen
• Curling the upper lip (Flehmen Response)
• Tensing the abdomen
• Changes in the color of the gums

Other symptoms of enteritis may include: ^{[6][7][12][13][14]}

• Diarrhea
• Weight loss or loss of body condition
• Swelling of the legs (stocking up)
• Swelling of the abdomen (ventral edema)
• Fluctuating appetite
• Mild fever
• Variable heart rate
• Excessive gas

Risk Factors

Enteritis is considered one of the most important equine medical conditions as it is a very common cause of disease and death in horses. ^[12]

Enteritis is most prevalent in Standardbred horses. ^[6] Typically, horses that develop this condition are young, usually under the age of 6. ^[6]

Other risk factors include: ^[12]

• Stress
• Recent hospitalization
• Transportation
• Previous or unresolved intestinal impaction
• Heavy parasite burden
• Recent history of general anesthesia
• Recent or recurring periods of fasting
• Contact with infected horses or environments (if the underlying cause is infectious)

Causes

The causes of enteritis are wide-ranging and not fully understood at this time. ^[6][12] In many cases, the cause cannot be confirmed and the horse must be treated based on its symptoms. ^[12]

Some cases of non-infectious enteritis are the result of poor feeding habits. ^[1] Horses that are overloaded with hydrolyzable carbohydrates (i.e. starch and sugars, such as when feeding grain-based diets) are at risk of developing enteritis. ^[1]

Other non-infectious causes of enteritis include: ^[1][12][15]

• Reaction to antibiotics
• Reaction to non-steroidal anti-inflammatory medications
• Poisoning, including blister beetle, hoary alyssum, arsenic, and castor oil toxicity
• Sand impaction
• Other types of impaction
• Gastroduodenal ulceration
• Peritonitis
• Stress
• General anesthesia
• Fasting
• Sepsis
• Nutritional imbalance
• Dietary indiscretion (eating substances outside of the usual diet)
• Overfeeding
• Lactose intolerance

Most cases of equine enteritis are caused by infectious agents. These include: ^{[1][6][14][15]}

• Salmonella
• Clostridium difficile
• Clostridium perfringens
• Neorickettsia risticii (also known as Potomac horse fever)
• Cyathostomiasis
• Strongyles
• Lawsonia intracellularis (also known as proliferative enteropathy)
• Rotavirus
• Coronavirus
• Rhodococcus equi
• Mycobacterium avium

Hypersensitivity to certain agents, such as food allergies, may also account for some cases of enteritis. ^[6]

Since some horses in the same family develop enteritis, it is theorized that there is a genetic component to this disease, but further research is required to confirm a genetic cause. ^[6]

Intro to Equine Nutrition

Gain a deeper understanding of your horse's nutrition needs. This free introductory course provides a foundation for horse owners to learn how to balance your horse's diet.

Enroll Now

Severity

There are several forms of enteritis. These range in severity depending on the virulence of the cause and the degree of inflammation. Severity may also vary depending on the presence of other symptoms and involvement of adjacent bodily systems.

Different forms of enteritis include: ^{[1][7][13][14][15]}

• Duodenitis-proximal jejunitis (also known as anterior enteritis and proximal enteritis)
• Eosinophilic enterocolitis/enteritis/colitis
• Necrotizing enteritis
• Antimicrobial-associated diarrhea
• Viral enterocolitis
• Bacterial enteritis
• Larval cyathostominosis (parasitic enterocolitis)
• Protozoal enterocolitis
• NSAID-associated Right dorsal colitis
• Granulomatous enteritis
• Lymphocytic-plasmacytic enterocolitis
• Multisystemic eosinophilic epitheliotropic disease
• Idiopathic focal eosinophilic enteritis

These distinctions may help guide treatment in some cases.

Diagnosis

Because the signs of equine enteritis are often vague and common to different conditions, many cases are treated without a confirmed underlying cause. ^[15]

Tools used to investigate enteritis in horses and guide treatment include: ^{[6][7][13][14]}

• Physical examination
• Blood tests
• Rectal palpation
• Gastrointestinal biopsy
• Fluid analysis such as abdominocentesis – the analysis of fluid extracted from the abdominal cavity
• Fecal analysis
• Nuclear scintigraphy (commonly referred to as a “bone scan,” but can be used to image other tissues)
• Absorption tests
• PCR tests
• Nasogastric intubation
• Ultrasound

Treatment

The treatment of enteritis aims to support the horse’s overall well-being and control the flow of toxins through the horse’s system as the inflammation runs its course. ^[1][7] If an underlying cause is confirmed, specific treatment of the root cause is also required.

Possible treatments include: ^[6][7][14]

• Gastric decompression
• Fluid therapy (either intravenously or orally)
• Anti-inflammatory drugs (either steroidal or non-steroidal)
• Anti-endotoxin therapies
• Anthelmintics (anti parasitic medications)
• Antidiarrheal medications
• Pain relief medications
• Vasodilation medications
• Prokinetic medications
• Nutritional support
• Antimicrobial therapies
• Transfaunation/fecal transplant

In cases where the disease only affects a small portion of the intestine, surgery may be the best course of action. ^[6] Surgical intervention may also be necessary in cases where swelling of the intestinal wall has blocked the passage of ingesta. ^[7]

Prognosis & Prevention

The prognosis for horses with enteritis is variable depending on the underlying cause, the degree of inflammation, and the ability to diagnose and treat a specific cause. Severe cases of enteritis are fatal even with aggressive therapy. ^[1]

Horses affected by enteritis due to infectious causes are at risk of spreading the infection to other horses. The risk of infectious enteritis underscores the important of maintaining robust biosecurity and quarantine protocols on the farm.

Strategies include: ^[15]

• Cleaning manure up quickly and thoroughly
• Isolating sick animals
• Avoiding sharing bedding and other items between animals
• Disinfecting tack, grooming and feeding equipment, and the environment

For some types of enteritis, vaccines are available to protect against the causal agents. ^[6] Some causes are preventable with biotherapies. ^[13]

Nutrition & Management for Intestinal Health

Maintaining intestinal health in horses requires both proper feeding and management. Important management considerations include providing consistent access to clean water, adequate turnout, and a clean, mold-free living environment.

Regular dental care is also important to ensure your horse can chew their food properly, promoting better digestion and nutrient absorption. Feeding horses smaller, more frequent meals can also help prevent digestive issues.

It’s also important to ensure your horse gets adequate fiber in their diet to support gut motility and hindgut function. Feeding a balanced, forage-based diet is one of the best ways to support gut health in horses.

After implementing these strategies to support your horse’s digestive health, you can also consider adding a digestive supplement to your feeding program. Yeast or probiotics are popular options for promoting hindgut health, as they help with fiber fermentation. Digestive enzymes also assist in breaking down food more effectively, ensuring better nutrient absorption and reducing the risk of digestive disturbances.

Mad Barn’s Visceral+® is a comprehensive digestive health supplement designed to support the stomach, hindgut, and immune system. This pelleted supplement is recommended by veterinarians to reduce the risk of digestive upsets and contains no grain fillers.

Visceral+

5 stars		86%
4 stars		5%
3 stars		4%
2 stars		2%
1 star		4%

538 Reviews

Learn More

• Our best-selling supplement
• Maintain stomach & hindgut health
• Supports the immune system
• 100% safe & natural

Summary

Enteritis is an umbrella term used to describe inflammation in the horse’s intestinal tract, specifically in the small and large intestines. Inflammatory bowel disease (IBD) is another term for enteritis and both terms are used widely to refer to intestinal inflammation throughout the tract.

• There are a wide variety of infectious and non-infectious causes of enteritis in horses, including viruses, parasites, bacteria, stress, sepsis, and poisoning
• Symptoms include colic, diarrhea, excessive gas, and lethargy
• Diagnosis of the underlying cause is not always possible, but general treatments to support digestive and overall health are often prescribed
• The prognosis for a horse with enteritis depends on the cause and severity of the inflammation
• Preventing enteritis involves maintaining strict biosecurity to stop infections, vaccinating against certain causes, managing stress, and providing excellent nutrition