Immune-Mediated Hemolytic Anemia in Dogs
Lethargy is one of the first signs of anemia in dogs
Understanding Immune Mediated Anemia in Dogs
In order to understand immune mediated anemia in dogs, dog owners must first understand anemia itself. Anemia occurs when there is a decrease in the number of red blood cells (erythrocytes) in the body. The main function of red blood cells is to carry oxygen to body tissues. When there is a decrease in the number of red blood cells, there is also a decrease in the levels of oxygen in the blood carried to organs and muscles, and this leads to weakness and fatigue.
Affected dogs, therefore, will tire easily, lose their appetite and become lethargic. Affected dogs will also have to breath faster and their heart will beat at a higher rate to keep up with the body's oxygen needs. Because in anemia, red blood cells have a decrease in oxygen, the blood is thinner, and therefore, the heart may develop a murmur when processing it as it flows faster. Because red blood cells give color to skin, anemic dogs may also have pale gums.
When is a Dog Clinically Considered Anemic?
According to Webmd, a dog is classified as anemic when its blood volume has a concentration of less than 37 percent by volume. Normally, in a healthy dog, the concentration would range between 39 to 60 percent. Here is a general guide to assess the severity of the anemia:
- Mild Anemia 30 - 37%
- Moderate Anemia 20 - 30%
- Severe Anemia 10 - 20%
- Critical Anemia< 10%
The blood test to determine the percentage of red blood cells is known as ''packed cell volume'' often abbreviated as PCV. In this test, basically, a drop of blood is spun in a special centrifuge which separates the red blood cells from the plasma.
Anemia is ultimately a symptom of an underlying disorder. In order to resolve anemia, affected dogs will need further testing to determine what is causing the lowered amount of red blood cells. This leads to diagnostic tests that help confirm or rule out immune-mediated anemia.
Diagnosing Immune Mediated Anemia
A variety of diagnostic tests are required to confirm or rule out Immune Mediated Anemia in dogs. Most vets have the dog undergo the following diagnostic tests:
- Complete blood count (CBC) This test, as the name implies, is a blood test that counts all the cells in the blood therefore including white blood cells (leukocytes), red blood cells (erythrocytes), and platelets (thrombocytes)
- Pack Cell Volume (PCV), also known as hematocrit (Ht or HCT) as previously mentioned, is the percentage of red blood cells in the dog's body.
- Reticulocyte counts basically measure the amount of immature red blood cells in the body. Red blood cells are typically released by the bone marrow when they are mature, however, in the case of anemia, they may be released when they are at an immature stage, and therefore known as ''reticulocytes''. This early release is to help the body overcome the chronic or severe loss of mature red blood cells. The presence of reticulocytes is generally a good sign since it confirms that the bone marrow is still functioning well.
- Coombs test: the Direct Coombs test is specifically used to test autoimmune anemia. This test determines if an immune mechanism is attacking the dog's blood cells. The blood is tested for an immune reaction to the blood.
Causes of Immune Mediated Hemolytic Anemia
Immune mediated anemia is a serious disorder where the dog's red blood cells are attacked by the immune system. The name of this disorder may sound intimidating, but if broken apart, it makes sense. As explained earlier, anemia means that there are reduced red blood cells carrying oxygen in the dog's blood. Immune mediated simply means ''caused by the immune system''. Hemolytic means ''destruction of the red blood cells''. So there you have it: an immune disorder causing the destruction of red blood cells in the blood, and therefore, anemia.
The immune system in healthy dogs is built to detect threatening foreign items such as germs, viruses, parasites and toxins. However, at times, the immune system decides to attack its own cells rather than just germs. When this happens, hemolytic immune-mediated anemia takes place.
Symptoms of Immune Mediated Hemolytic Anemia in Dogs
As previously mentioned, dogs suffering from this disorder will develop symptoms of anemia, due to lower red blood cells circulating, and therefore, reduced flow of oxygen in the blood. This causes the following health problems:
- Lack of appetite
- Increased heart rate
- Increased breathing
- Heart murmur
Due to the destruction of red blood cells, a dog suffering from immune-mediated hemolytic anemia may also develop ''icterus'' aka ''jaundice'' where a yellow tint to gums, skin and eyes takes place and ''bilirubinuria'' where the dog produces brown urine due to hemoglobin release from damaged red cells.
Treatment of Immune Mediated Hemolytic Anemia in Dogs
Because the immune system is over reactive the main treatment focuses on suppressing the immune system's response. This is accomplished through the use of corticosteroids such as prednisone, prednisolone and dexamethasone. These medications come with side effects such as increased eating, increased drinking and increased urination. In severe cases, blood transfusions may help restore a good part of the lost red blood cells.
The prognosis varies depending on how the dog responds to treatment and how severe the anemia is. The condition is severe and can be life threatening.
Disclaimer: If your dog is sick, please refer to your veterinarian for a hands on assessment and advice. Please do not rely on online resources to diagnose and treat your dog. By reading this article you accept this disclaimer.
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© 2012 Adrienne Farricelli