Viral Diarrhea (Foals) in Horses

Viral Diarrhea (Foals) in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost
Viral Diarrhea (Foals) in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

What is Viral Diarrhea (Foals)?

In most cases, viral diarrhea in foals is caused by the rotavirus. It is extremely contagious to other animals; therefore, at the first sign of diarrhea or illness in your foal, he should be isolated. The rotavirus causes malabsorption within the small intestine and therefore certain things get passed on to the large intestine that should not be there which leads to gastrointestinal upset, hence the diarrhea. The first symptom you may see from your foal may be depression or anorexia, or in some cases, the foal will develop the diarrhea first. Supportive therapies should be started immediately to ensure his condition does not worsen. Your foal may need to be hospitalized in order for him to receive 24 hour care and observation; otherwise he might not survive.

If your foal is suffering from diarrhea, one possible culprit could be a virus. It should be treated as a medical emergency because his condition can decline very quickly, leading to a life threatening one.

Symptoms of Viral Diarrhea (Foals) in Horses

Severity of symptoms can vary in each foal.

  • Depression
  • Anorexia
  • Watery feces, profuse amounts 
  • Dehydration
  • Death 

Symptoms can last anywhere between 4 to 7 days or can last for weeks. The younger the age of the affected foal, the more severe his symptoms and condition will be.


There are multiple viruses that can cause diarrhea in foals but rarely cause effects in adult horses. The rotavirus is the main cause of a foal’s viral diarrhea however other viruses have been thought to cause it as well. In most cases, the foal experiences symptoms for 4 to 7 days but in more severe cases, the diarrhea can persist for weeks.



Causes of Viral Diarrhea (Foals) in Horses

There are villi in the small intestines of every animal and human, with the job of nutrient absorption. The rotavirus destroys the tip of the villi leading to malabsorption and lactase deficiency. Since the lactase cannot be absorbed, it passes on through to the large intestine, a place it should not be, and induces osmotic diarrhea.



Diagnosis of Viral Diarrhea (Foals) in Horses

The veterinarian will collect a sample of his feces to run diagnostic tests on it. Looking at a sample with an electron microscope will assist with virus identification as well as an immunoassay test for detection of rotavirus. Collecting a sample early on in the illness will improve the chance of virus detection.

Running routine blood work will also be helpful in determining how your foal’s body is handling the virus. A complete blood count and chemistry panel will give the veterinarian a look at how the foal’s internal organs are handling the virus. A packed cell volume may also be completed to check his hydration status.



Treatment of Viral Diarrhea (Foals) in Horses

If your foal is suffering from viral diarrhea, treatment is mainly supportive. Fluid therapy with electrolytes will be started to ensure he does not become dehydrated. The electrolytes will give his immune system the extra boost it needs to combat the virus. Ensuring he continues to eat is also important. He will need the nutrients to keep him strong and his immune system working. It is also important that he eats so that his GI system continues to flow and move, otherwise, he may develop colic.

Containment is also important when treating viral diarrhea in your foal. He will be highly contagious and isolation is imperative to not spreading the illness. Keeping him isolated in one stall throughout his sickness and away from other animals in ideal. People cleaning the stall should wear personal protective equipment that can either be disposed of or disinfected easily. While the foal is in the stall, you should place foot baths outside of it to ensure not to transfer the virus to other areas by your shoes. Keep designated equipment for cleaning separate so as to not accidentally use it in a healthy animal’s stall. There are specific, strong cleaners recommended for disinfection of contaminated areas. If your stall has a dirt floor, decontamination will prove to be more difficult and may require you to remove the top layers of dirt to ensure virus removal from the area. 

Keeping him isolated will also help in his recovery process. It will provide him with a calm, quiet place to rest and decrease stress. It will also decrease his chances of becoming ill with another sickness in addition to the diarrhea if he is away from other animals that may be a carrier. His immune system will already be susceptible so decreasing his chances of becoming infected with another virus or bacteria is ideal. 

There is a vaccine available for pregnant mares which is said to induce colostral antibodies to reduce the risk of rotavirus.



Worried about the cost of Viral Diarrhea Foals treatment?

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Recovery of Viral Diarrhea (Foals) in Horses

As long as your foal continues to eat, drink, and receive necessary supportive care, he should recover without long term side effects. If he stops eating, drinking, or becomes lethargic and unresponsive his prognosis of recovery declines severely. In some cases, a foal can suffer from the virus so severely he will need to be hospitalized and receive intensive care in order to survive.



Viral Diarrhea (Foals) Questions and Advice from Veterinary Professionals

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