Diarrhea is a relatively common condition in horses and often underestimated by the owner.It can be fairly benign (soft dung, emission of a little water) to dramatic (liquid crops in abundance, foals …) and lead to severe dehydration associated with a state of shock. The reasons are varied and it is not easy to obtain a diagnosis of certainty. We distinguish acute diarrhea, which occurs suddenly, often more severe, of chronic diarrhea settling more gradually and persisting in time, better tolerated but more difficult to diagnose and treat.
General information on the digestive tract of the horse
The horse’s digestive tract consists of the esophagus, the stomach, the small intestine (duodenum, jejunum and ileum) and the large intestine (caecum, ascending colon and descending colon).
The large intestine represents more than 60% of the intestinal volume , which is a peculiarity of the horse. It is in fact this part of the digestive tract that allows them to digest and thus to value vegetable substances, such as cellulose.
To function properly, the large intestine needs ballast: a large supply of fodder throughout the day makes chewing long and sufficiently saliva the horse, and allows a very good stimulation of digestive motor skills.
The role of the intestine , as in other species, is to absorb water and nutrients from food. If it does not work properly, especially in case of diarrhea, the water is not well absorbed and is eliminated directly, causing dehydration of the horse, severe in case of acute diarrhea. The same goes for nutrients, with a loss of protein.
For the record, the horse is unable to vomit.
In fact, the junction between the esophagus and the stomach only works in one direction.
Feeding in the horse’s digestive tract:
Symptoms of horse diarrhea
All the symptoms observed are generally common to the various causes of diarrhea. The horse has soft, liquid dung, often associated with more or less severe dehydration if the diarrhea is acute. One can observe in parallel of the fever , a lack of appetite even an anorexia, a depression , an abdominal pain (colic) in the horse.
A diarrhea of the horse is considered chronic from the moment it persists for 7 to 14 days.
A weight loss of the horse sometimes associated with subcutaneous edema usually accompanies chronic diarrhea. A diarrhea of the horse is considered chronic from the moment it persists for 7 to 14 days , up to weeks or even months.
Causes of horse diarrhea
It is mainly the caecum and the colon that are affected, because this is where most of the reabsorption of water takes place . The causes of these intestinal disorders are numerous and varied:
- Bacterial infections:
Often associated with fever, they produce severe and rather acute diarrhea in the horse:
- Salmonellosis ( Salmonella ssp ):
Salmonellae are highly contagious bacteria that cling to the intestinal wall of the horse and secrete enterotoxins and cytotoxins. These toxins increase the secretion of fluids in the intestine and damage intestinal cells inducing profuse horse diarrhea. These damaged cells then pass from enterotoxins to the rest of the body causing general effects (fever for example). Many horses are healthy carriers, and the disease is triggered especially in case of transit disorders. This infection is very serious, difficult to treat, and can go as far as the horse’s death.
- Clostridium ( Clostridium perfrigens, C. difficile ):
These bacteria are part of the commensal (ie normal) flora of the horse’s digestive tract , and when it is unbalanced, they develop in large numbers and are then responsible for intestinal disorders . Like salmonella, perfringens produces enterotoxins that damage intestinal cells and induce hypersecretion of fluids in the intestinal lumen. One of the toxins causes severe inflammation of the intestine as well as necrosis . Diarrhea is intense and often haemorrhagic that can quickly lead to the death of the animal.
- Lawsoniose ( Lawsonia intracellularis ): it mainly affects the foal for up to one year. It can induce very fluid and profuse diarrhea , as well as subcutaneous edema and slimming . The treatment is long but the chances of success are good if the case is taken on time.
- Potomac Horse Fever (Ehrlichia risticii): anecdotal in France.
- Parasitic infections:
Diarrhea in general chronic, not very intense.
- Strongylose :
Migrations of larvae of “ strong strongles ” ( Strongylus vulgaris, S. edentatus, S. equinus ) through the intestinal wall cause diarrhea by inflammation of the intestinal wall. Indeed, the influx of inflammatory cells increases the secretions of fluids and the absorption capacities are decreased.
- Cyasthostominosis :
Larvae of “small strongles” are encysted in the intestinal wall to spend the winter in infected horses. At the return of spring, the larvae emerge and cause bleeding, ulcers and intestinal inflammation. This induces diarrhea by disturbing intestinal secretions, as for strongylosis. It is the most common cause of chronic diarrhea in horses .
- The use of non-steroidal anti-inflammatory drugs (NSAIDs): Their use disrupts the regulation of intestinal pH and decreases cell renewal. This can lead to diarrhea in case of overdose and / or prolonged use of NSAIDs.
- Of toxic causes as ingesting acorns, ferns.
- A grain overload , usually associated with laminitis and colic.
In case of chronic diarrhea of the horse, to the other causes already developed above, are added:
- The tumor causes (food lymphosarcoma, granulomatous enteritis or colitis, enteritis or colitis, eosinophilic …)
- A chronic peritonitis (abdominal inflammation, causing bowel dysfunction and abdominal pain)
- The ingestion of sand
- A chronic colitis nonspecific (inflammation of the lining of the colon)
- Changes in the digestive commensal flora
- Various extra intestinal causes: liver, kidney, etc.
However, determining the cause of chronic non-parasitic diarrhea is a real challenge for the veterinarian, and only accomplished in 60-70% of cases, and often after the horse’s death.
The treatment can be broken down into several objectives:
1) Control of the consequences of diarrhea on the body
- Rehydration and Electrolytic Rebalancing
Diarrhea can induce severe dehydration in the horse and a loss of important mineral salts, in fact, they are induced by a call of water in the intestine. The first reflex to have is therefore to put the horse under perfusion : the water requirements are such that rapid rehydration by oral route is impossible.
- Intestinal Protectors
Intestinal dressings , antacids … to protect the intestinal mucosa of the horse.
- Antipyretics in case of fever
2) Relieve pain:
The dipyrone , associated or not with the butylscopolamine makes it possible to limit the intestinal spasms frequently associated with the diarrhea of the horse. In cases of violent colic, tranquilizers may also be administered.
3) Fighting the cause:
- Fight against infection
In case of bacterial cause , the use of antibiotics (for Clostridiosis, or Lawsoniosis) is prescribed. For Salmonellosis the use of antibiotics is controversial.
- Fight against infestation
To get rid of cyathostomes and strobiles in the horse , the veterinarian prescribes dewormers, called anthelmintics (ie against helminths which are a class of worms) . From a prevention point of view, it is best to plan a year-round de-worming plan for the horse with its treating veterinarian. Due to the development of many resistances, it is advisable to treat in a reasoned way, taking into account not the individual but the herd , the place of life and integrating coproscopies .
- Fight against inflammation
The endotoxins released by the bacteria cause inflammation of the intestinal wall of the horse. The flunixin meglumine in small doses , the meloxicam or the firocoxib can fight against this inflammation while being relatively well tolerated (NSAIDs may indeed be factors diarrhea!)
- Re-seeding of the digestive flora
This is essential in the intestinal equilibrium of the horse . One can support it with probiotics or even by causing the horse to eat healthy horseshoe.
In case of chronic diarrhea , we add to this a nutritional management of the horse, which aims in particular to:
- Rebalance the diet to meet the actual nutritional requirements of the horse: many of them have higher protein requirements to cover due to losses from diarrhea, and are deficient in energy, minerals and vitamins.
- Give good proportions different types of hay so as to reduce the mechanical and physical work of the colon. Distribute the hay at will .
- Reduce stress with a pace of distribution, adequate meal size, and time spent in the paddock (grass).
- Increase the proportion of omega 3 in the diet
- Avoid excess carbohydrates in hay and concentrate
Warning food transition should be gradual , otherwise the risk of disrupting the digestive commensal flora and thus further promote diarrhea in horses.
A study carried out in 2012 shows convincing results by simply combining this nutritional management with the administration of sulfasalzine , a prodrug often used in the treatment of inflammatory bowel diseases (human and veterinary). But the mechanism behind its anti-inflammatory effect is still poorly understood today.
The diarrhea of the horse is always to be considered as an emergency , the condition of the horse can very quickly degrade in case of profuse diarrhea. In the absence of early treatment, recovery is long. Chronic diarrhea is a real diagnostic and therapeutic challenge for veterinarians.
In order to prevent diarrhea, it is important to maintain a healthy digestive commensal flora, in particular by ensuring the diet and its mode of distribution.