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Also Known As

Aplastic anemia, Bloodlessness, Low red blood cell count (RBC)


Anemia is one of the most commonly misdiagnosed problems in horses, not because the anemia is difficult to diagnose, but because of many possible causes. The diagnosis of equine anemia is based on clinical signs that indicate reduced oxygen being transported to tissues and a reduced packed cell volume (PCV) which measures the percentage of circulating red blood cells in the bloodstream.

Normally a horse has a PCV of about 40 percent with some age and breed variations. A horse with a PCV of less than 30 percent is considered anemic and efforts should be made to identify the cause of the lack of red blood cells.

In the case of Equine Infectious Anemia (EIAV), the virus reproduces in white blood cells, leading the immune system to create antibodies that attack and destroy red blood cells.


  • Fatigue
  • Shortness of breath
  • Elevated heart rate
  • Pale mucous membranes
  • Discolored or reddish urine
  • Weak pulse
  • Nose bleeds
  • Exercise intolerance and weakness
  • Decreased appetite
  • Weight loss
  • Ventral edema
  • Abortion


While the diagnosis of anemia in horses is often straight forward involving a blood sample and centrifuge, the challenge is in determining the cause of the anemia. Anemia related to acute blood loss through trauma or hemorrhage is easily identified and controlled since the cause is obvious.

On the other hand, anemia due to parasites, ulcers or other conditions may be less easy to diagnose because it is hidden from direct observation.

Other common causes of anemia in horses are related to infections ranging from pneumonia to renal disease. Several viruses and cancers may clinically manifest as anemia especially in early stages. Less frequently, deficiencies in iron, copper, protein and B vitamins impair the horse's body's ability to manufacture red blood cells.

Some plants are toxic and if eaten over a period of time, this toxicity causes anemia. Over-usage of anti-inflammatory drugs and some neonatal conditions are also causes of anemia.

In the case of equine infectious anemia, horse flies, mosquitos and deer flies often transmit the virus, or it may be transmitted via blood transfusion, in-utero passage from mare to foal or through semen or milk.


Obviously anemia will affect a horse's level of energy and general well-being. A proper diet is especially important both for preventing anemia and in healing the body when injuries, ulcers, infections, or illnesses have caused either loss of blood or destruction of red blood cells.

Veterinarians often recommend oats and oat extracts which are considered to have remarkable properties and have a beneficial effect on the horse's digestive system.

A clean, well-kept environment that protects the horse from biting insects and accidental injuries along with care to make sure that stable and pasture mates are healthy to prevent contagious diseases such as equine infectious anemia from infecting a horse prone to anemia .


Whenever anemia is suspected, the source of the anemia should be determined, and blood tests should be done to determine the packed cell volume (PCV). If the anemia is due to acute blood loss, the source of the trauma or hemorrhage should be identified and controlled. A veterinarian should be contacted immediately to perform a complete physical examination, take blood samples and possibly give a blood transfusion.

If Equine Infectious Anemia is suspected, the Coggins test which checks for antibodies in the horse's blood should be performed. Horses that test positive on the Coggins test or that have symptoms of the viral infection should be quarantined.

A healthy diet prescribed by a veterinarian should be part of the treatment in case of mineral or vitamin deficiencies or infectious illnesses that deplete red blood cells. Hay should be clean, mold-free and of the variety recommended by a veterinarian. .

The diet may include amino acids including glutamine and threonine and yeast extracts to provide protection to the horse's system. Any infections should be cleared up as promptly as possible and steps taken to prevent insect bites or ingestion of parasites.

Awareness of any changes in level of activity, as well as awareness of the variety of symptoms of anemia will help the horse owner take the necessary steps to keep the horse healthy and energetic.

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EquiMed Staff

EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.