Foal Diarrhea

Causes of diarrhea in foals

Foal heat diarrhea: This is a mild form of diarrhea that occurs in foals between 5 and 14 days of age, around the time the mare has her “foal heat”. This type of diarrhea is self-limiting and does not require treatment.

Viral diarrhea

The most common virus causing diarrhea in foals is rotavirus, which is highly contagious between foals. Affected foals have profuse, watery diarrhea, which can be mild to severe. They may become dehydrated, depressed, and anorexic. There is a vaccine available for pregnant mares which may help lessen the severity or prevent the disease in foals. This virus has been associated with gastric ulceration and therefore, gastroprotectants are an important part of the treatment of rotavirus. A fecal sample is required for definitive diagnosis and these foals should be treated by a veterinarian.

Bacterial diarrhea

There are many types of bacteria that can cause diarrhea in foals and while there is a wide range of severity, all foals with bacterial diarrhea should be treated by a veterinarian.

  • Clostridium perfringens & Clostridium difficile: Clostridial organisms release toxins that cause intestinal damage and profuse, watery diarrhea that may be red tinged or bloody. These organisms can cause diarrhea in horses of any age and foals with this disease may also exhibit signs of colic and dehydration.
  • Salmonella species: This is often seen in septic foals and diarrhea caused by salmonella can vary from scant to profuse. The diarrhea is often accompanied by fever and signs of colic and this organism can cause diarrhea in horses of any age.
  • Rhodococcus equi: This organism usually manifests as respiratory disease in foals 1 to 4 months of age but can also cause chronic diarrhea.
  • Lawsonia intracellularis: Usually seen in weanlings and yearlings, this bacteria causes depression, weight loss, edema, and colic in addition to diarrhea.

Protozoal diarrhea

Cryptosporidium is a protozoal pathogen that generally causes self-limiting diarrhea in foals unless their immune system is already weakened by a concurrent disease.


Many causes of diarrhea can be made by performing laboratory analyses or bacterial culture of the feces itself. Blood work and abdominal ultrasound may also aid in diagnosis and help determine the severity and extent of disease.

Treatment of diarrhea in foals

Treatment depends on the cause and severity of diarrhea. Foals with diarrhea may become dehydrated and require intravenous fluid therapy. In severe cases, foals with diarrhea should be hospitalized for aggressive therapy and constant monitoring. Intestinal protectants and gastric ulcer prevention are other important aspects of nursing care for foals with diarrhea. Most of these foals will require antibiotics directed towards the cause of the diarrhea. In the majority of cases of foal diarrhea, accurate diagnosis and early treatment will help lessen the severity of disease.


As many causes of diarrhea are contagious to other horses, foals with diarrhea should be isolated from herd mates. The use of gloves, boots and a foot bath outside the stall are helpful in preventing the disease from spreading to other horses on the farm. Please don’t forget that many of these organisms also have the potential to cause disease in humans and therefore wearing gloves and frequent hand washing are very important when handling foals with diarrhea.

Lauren Danskin, DVM – 1/27/12

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