Anemia in Horses

Last Updated on March 29, 2022 by Allison Price

Anemia is when there is a decrease of red blood cells. This can be measured using hemoglobin concentration or red blood cell count. Anemia can result from the destruction or lack of production of red cells. Anemia can be classified as either regenerative, or non-regenerative. A regenerative type of anemia is when the bone marrow reacts to a decrease in red blood cells by producing more red blood cells. Anemias caused by bleeding or the loss of red blood cells is usually regenerative. A nonregenerative is one in which the bone marrow does not respond adequately to an increased demand for red blood cells. Nonregenerative anemias are those that result from a decrease of erythropoietin, the hormone that stimulates red cell production.

Anemia can be caused by some infections, such as babesiosis and trypanosomiasis.

Signs and symptoms of anemia

Anemia signs in animals vary depending on their severity, duration (short-term or long-term), and the underlying cause. If more than a third is lost quickly and the blood volume cannot be replaced, sudden anemia can cause shock and even death. Rapid blood loss can cause an animal to have a higher heart rate, pale gums and low blood pressure. The animal might appear yellowish if red blood cells are destroyed. Long-term anemia has taken time for animals to adapt and the signs they experience are often slower to manifest. They may experience loss of energy, weakness, or loss of appetite. Similar physical examination results will be seen in affected animals, including pale gums, increased heart rate and possibly a murmur.

Anemia diagnosis requires a complete medical history. The following questions may be asked by a veterinarian:

  • What length of time have these signs been around?
  • Do you know if the horse has been exposed to poisonous plants, chemicals or heavy metals in the past?
  • What vaccinations and drug treatments has the horse received?
  • Where has the horse travelled?
  • Are there any underlying illnesses that the horse has had?

Your veterinarian will perform a complete blood count to determine the severity of anemia, bone marrow response and condition of other blood types. To determine red blood cell size, shape, and check for red cell parasites, a test should be done.

Anemia in Horses

To assess the health of internal organs, additional blood and urine tests may be performed. An examination of the animal’s stool under a microscope can reveal trace amounts of parasites and blood loss. A coagulation profile is a test that looks at the ability of the blood to clot. Bruising and bleeding could be signs of a condition or disease. Other tests may be required if hemolytic disease is suspected. This is a condition where red blood cells are destroyed. Anemia can also be diagnosed by a blood test for infection. An animal suffering from an undiagnosed, non-regenerative anemia may need to be evaluated by a bone marrow specialist.

Regenerative Anemia

Hemolytic anemia and blood loss anemia are examples of regenerative anemias.

Sudden and severe bleeding can cause shock and death if the condition isn’t treated promptly with intravenous fluids, blood transfusions, and/or both. A major injury or surgery are obvious causes of severe blood losses. Your veterinarian will examine the cause of blood loss if it is not obvious. This could include conditions that affect blood’s ability or stomach ulcers or other causes. Iron-deficiency is a condition that results in long-term, low-grade blood loss.

Anemia caused by the destruction of red blood cells is called hemolytic anemia. They are often regenerative. They are usually regenerative.

Neonatal Isoerythrolysis causes newborn foals to lose their red blood cells. This happens when foals are fed from mothers whose colostrum, a yellowish liquid rich in minerals and antibodies that is produced shortly after birth, contains antibodies to their newborn red blood cells. It can also be caused by the mother being exposed to another blood type in a previous pregnancy, or unmatched blood transfusions. Horses are usually affected by A, C and Q. Most commonly, this is seen in Thoroughbreds or mules. When foals start nursing, they are able to absorb the antibodies. Once the antibodies are absorbed, they enter the bloodstream and attach to red blood cell membranes. This causes them to burst. Neonatal hemolytic anemia is a condition in which newborns born with neonatal iterolysis have normal births but experience severe hemolytic anemia within 1-2 days. Anemic foals are weak and jaundiced. To confirm the diagnosis, a veterinarian may perform tests. The treatment involves stopping the colostrum and providing supportive care with transfusions. Before the baby is allowed to have maternal colostrum, a veterinarian can test it. You can avoid neonatal isoerythrolysis by withholding colostrum if the foal has a known reaction.

Nonregenerative Anemias

Anemias that are not regenerative include those caused by nutritional deficiencies (such as iron), longterm diseases, kidney disease, primary bone marrow disease, and other chronic conditions.

Anemia due to nutritional deficiency occurs when nutrients required for red blood cell growth are lacking in sufficient amounts. Anemia can develop slowly and may be initially regenerative but eventually becomes non-regenerative. Anemia can be caused by starvation, vitamin and mineral deficiencies, inadequate energy intake and insufficient protein intake. Anemia due to iron deficiency is not common in horses. It is usually not due to inadequate iron intake. It is usually caused by long-term, low-grade blood loss. This disorder can be treated by your veterinarian with iron supplements as well as by diagnosing and treating the source of the blood loss.

Anemia due to a chronic (chronic) condition usually causes mild to moderate drops in red blood cell count. This is the most common type of anemia in animals. Anemia can result from long-term inflammation, infection, tumors, liver disease or hormonal disorders, such as Cushing disease. Cytokines are proteins produced by inflammation cells. They can cause a decrease in iron availability, red cell survival and bone marrow regeneration. The treatment of the underlying condition can correct the anemia.

Nonregenerative anemia is common in animals with long-term kidney disease. The kidney measures how much oxygen is being received by the tissues and produces erythropoietin. This hormone stimulates the formation of red blood cells in bone marrow. Anemia can occur in horses suffering from chronic (long-term) kidney disease.

Bone Marrow Diseases

Nonregenerative anemia can result from bone marrow failure or disease. This could lead to a decrease in all blood types, including red, white and platelets. White blood cells are the most affected by widespread involvement of the marrow, followed closely by platelets and then red blood cells.

Aplastic Anemia is severe bone marrow disorder. This means that bone marrow is less able to produce blood cells. Pancytopenia is a condition that causes a reduction in red blood cells, white cells and platelets in blood. It is also common in horses with underdeveloped marrow and fat replacement. Although most cases are undiagnosed, it is possible to be caused by drugs, radiation therapy, or immune-mediated diseases. By sampling bone marrow, the condition can be diagnosed. The underlying cause of the condition must be identified and treated. Sometimes, support care like antibiotics or transfusions is required. Other drugs can also be used until the bone marrow heals. Bone marrow transplantation can be helpful, but it is not a common procedure.

Pure red cell aplasia results in a decrease in both mature and immature blood cells. Other types of blood cells do not suffer from the same effect. This nonregenerative anemia results in a drastic reduction of elements responsible for the production of red blood cells from the bone marrow. Immune-related cases often respond to immunosuppression therapy. For severe cases, blood transfusions may be recommended. This condition can be caused by recombinant humanerythropoietin. It is used to treat kidney failure and illegally boost the performance of race horses. Some animals may recover if the drug is stopped.

Primary Leukemias is a form of cancer where abnormal white blood cells replace normal ones. This can lead to anemia, a decrease in normal white blood cells and decreased platelets. Although primary leukemias are rare or uncommon in domestic animals, they have been reported in horses. Leukemias can be classified as either acute (sudden, often very severe) or chronic (long-lasting, with less severe signs). The most common form of acute leukemia is one in which the marrow contains immature blood cells. These cases respond poorly to chemotherapy. Remission times in animals that respond are often short. Chronic leukemias are those with a high level of production of one blood line. They are less likely than anemia to occur and respond better to treatment.

Allison Price
Allison Price

I’m Allison, born and raised in San Diego California, the earliest memory I have with horses was at my grandfather’s farm. I used to sit at the stable as a kid and hang out with my Papa while he was training the horses. When I was invited to watch a horse riding competition, I got so fascinated with riding!