Ron Hines DVM PhD 4/21/06

Blood is composed of a liquid portion, the plasma, and a cellular portion. The cellular portion is composed of red blood cells or erythrocytes, which carry oxygen throughout the body, platelets that allow the blood to clot and white blood cells, which fight disease. Anemia is the presence of too few red blood cells. Most cases of anemia are the result of some other disease at work within the body.
There are two classifications of anemia. In the first, the body loses blood faster than it can be regenerated but is still able to produce new red blood cells (RBCs) in the bone marrow. This is called regenerative anemia. In the second form, the body has lost the ability to make new RBCs in the bone marrow. This is called non-regenerative anemia. A mark of regenerative anemia is that the body releases some RBCs a bit too early. These young RBCs are called reticulocytes.
Anemic pets must breath faster to keep their bodies oxygenated and their heart beats faster. They often have low energy levels and pale or yellowish gums.
You will see that the gums or mucous membranes are pale when your pet’s lip is lifted up. Eyes and ears may be pale as well. Anemic animals often become weak, depressed, sleep more than normal. They may stop grooming themselves, have a decreased appetite, and have increased panting.
Because animals with anemia have fewer red blood cells, their blood is thinner. As a result, anemic animals can develop heart murmurs. The noise a heart murmur makes comes from the turbulent sound thinner blood makes as it flows through the heart.
Clinical signs of anemia depend on the severity of the disease and how quickly the anemia occurred. With gradual anemia, the body has the time to adjust to the decreased red blood cell count. Animals that become anemic very quickly may die because their bodies cannot handle the sudden loss in red blood cells and oxygen.

Diagnosis:
When I suspect that a pet is anemic, I perform a blood test to determine the number of erythrocytes present in the animal’s bloodstream. The test for anemia is called a "packed cell volume," or PCV. A drop of blood is introduced into a thin glass tube and spun in a centrifuge to separate the red blood cells from the blood serum or plasma. The shorter the column of red cells, the more anemic the pet is. I also stain and examine a thin film of blood on a slide to determine the characteristics of the red cells and blood platelets that are present. In this way, I can distinguish between regenerative and non-regenerative anemias.

Regenerative anemias mean that the body is producing new red blood cells to replace those that were lost. Many of these cases have a better outcome than non-regenerative anemias in which the body is unable to produce new red blood cells. I almost always run a blood serum analysis and a white blood cell count on anemic animals to help me determine the cause of the disease. In non-regenerative anemias it may be necessary to examine samples of the blood-forming marrow of the bones.

Regenerative Anemias

Blood Loss Anemia: The most common cause of regenerative anemia in young animals are intestinal parasites (hookworms). Another common cause of anemia in young pets is heavy flea infestation. Although each flea only sucks a minute amount of blood the combined loss of blood in immature animals can be great. Hemoglobin, the red pigment of blood, contains iron. In both instances so much iron is lost from the body that the red blood cells subsequently produced are smaller than normal (microcytic anemia).
The most common cause of blood-loss anemia in adult dogs and cats is traumatic blood loss due to a large wound. In older pets these blood-loosing “wounds” are often the result of bleeding cancers of the walls of the gastrointestinal tract or urinary system. Another cause of blood loss – especially in dogs – is the administration of non-steroidal anti-inflammatory medications including aspirin, ibuprofen, phenylbutazone and naproxen and pyroxicam. These medications can cause bleeding ulcers of the stomach and small intestine leading to anemia.

In ferrets, sudden bleeding into the intestinal tract (acute hemorrhagic gastroenteritis) is the most common form of blood loss. Occasionally, this is due to the ingestion of sharp foreign material. More commonly, it is the result of stress or bacterial intestinal infections (campylobacter, salmonella).d
Ferrets are also very subject to blood loss anemia due to heavy flea infestations.

Mild to moderate cases of anemia are treated with blood-building vitamins and minerals called hematinics. Severe cases of anemia require transfusions. Luckily, transfusion reactions are less common in cats and dogs than in human beings.
Hemolysis: Hemolysis is the destruction of red blood cells within the veins and arteries of the body. This can be caused by the ingestion of toxic materials, bacterial and viral infections, defectively produced red blood cells, autoimmune disease and parasites of the blood (Haemobartonella and Babesia). These are often sudden crisis events. Transfusions are not effective in treating hemolysis because the new blood is destroyed as quickly as it is added. Cases of hemolytic anemia are treated with antibiotics and drugs that slow the destruction of red blood cells (corticosteroids). The gums and white portions of the eyes of animals with hemolytic anemia are often yellow (ictric) due to the presence of excessive destroyed hemoglobin products within the body (bilirubin). Both Tylenol (acetaminophen) and onions can cause anemia in cats. Accidental eating of zinc-based coinage (pennies) will cause anemia in all species of animals.

Non-regenerative Anemias
Ferrets: The most common cause of non-regenerative anemia in ferrets is elevated blood estrogen levels in unsprayed female ferrets undergoing prolonged heat periods. Non-regenerative anemia is also sometimes seen in the leukemias and adrenal cell tumors common in these pets.

Feline Leukemia Virus: Often, the first signs of Feline leukemia (FLV) in cats are chronic low-grade fevers and anemia. This anemia is due to the effects of the FLV on the blood forming elements within the bone marrow.

Feline Immunodeficiency Virus: As with FLV, feline immunodeficiency virus (FIV) often causes anemia in cats through its effect on bone marrow. Complicating matters, cats with FIV often have poor appetites and will not eat a balanced diet. Diets low in iron, and vitamin B-12 exacerbate these anemias.

Feline Abscesses: Indoor/outdoor cats that fight as well as un-neutered tomcats are very susceptible to septicemias (bacteria in the blood stream) and subcutaneous abscesses. These often result in toxic, non-regenerative anemias early in the condition. Once the infections coalesce into abscesses, the anemia subsides unless the pets are already positive for FLV, FIV or both these virus.

Cancers: Many forms of cancer liberate toxins into the bloodstream that suppress the formation of blood in the bone marrow. Generally, cancers that cause anemia are the most life-threatening forms of cancer. Small, benign tumors do not cause anemia. In certain types of cancer, erythropoietin production by the kidneys as well as its activity on the bone marrow is inhibited by cancer-produced cytokines (the substances that mediate inflammation) as well as by chemotherapy drugs.

Kidney Failure: Kidney failure in animals leads to a buildup of toxic waste in the blood stream that suppresses blood cell formation. In chronic renal failure, the pet’s kidneys cease to produce sufficient amounts of a hormone, erythropoietin, necessary for blood cell formation in the bone marrow. Human erythropoietin has been available since 1989. However, it has not worked well as we had hoped in animals because each animal’s native erythropoietin is slightly different from the human form and most cats eventually build up immunity to human erythropoietin.. The lives of cats suffering from non-regenerative anemia can often be improved by administering synthetic (recombinant) feline erythropoietin (rfEPO) developed at Cornell Veterinary School. Studies on the use of canine erythropoietin have also been underway at this School since 2001.

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