Ron Hines DVM PhD 4/24/06

The dynamics of anemia in ferrets is the same as anemia in all warm-blooded animals as well as people. 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 ferret 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 ferret 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 ferrets must breath faster to keep their bodies oxygenated. Their hearts beat 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 ferret’s lip is lifted up. Its eyes and ears may be pale as well. Anemic animals often become weak, depressed and sleep more than normal. They may stop grooming themselves, have a decreased appetite.
Because ferrets with anemia have fewer red blood cells, their blood is thinner. As a result, anemic ferrets often have heart murmurs. The noise a heart murmur makes comes from the turbulent sound thinner blood makes as it flows through the heart valves.
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 numbers. Ferrets that become anemic very quickly may die because their bodies cannot handle the sudden loss in red blood cells and oxygen.
Diagnosis:
The three most common causes of anemia in ferrets are heavy flea infestation, lymphoma tumors and estrogen-induced aplastic anemia. Estrogen-induced aplastic anemia was very common when ferrets were sold unspayed.
When I suspect that a ferret 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 (aplastic) anemias.
Regenerative anemias mean that the body is producing new red blood cells to replace those that are being 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 blood-loss anemia in ferrets is heavy flea infestation. The tendency of ferrets to snuggle in towels and blankets in their cage make them an ideal host for fleas. Usually it is the cat flea, Ctenocephalides felis, which parasitizes dogs and cats that is the problem. Although each flea only sucks a minute amount of blood, the combined loss of blood can be very 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).
In ferrets, sudden bleeding into the intestinal tract (acute hemorrhagic gastroenteritis) is another type of blood loss. Occasionally, this is due to the ingestion of sharp foreign material. But more commonly, it is the result of stress and bacterial intestinal infections (Campylobacter, Salmonella).
Mild to moderate cases of anemia are treated with blood-building vitamins and minerals called hematinics. Severe cases of anemia can require transfusions or artificial blood substitutes. When I saw many unspayed female ferrets with estrogen-induced aplastic anemia I transfused them with an artificial blood substitute designed for Jehovah’s Witnesses (Flusol DA20).
Hemolysis: Hemolysis is the destruction of red blood cells within the veins and arteries of the body. In ferrets this is usually caused by the ingestion of toxic materials. Some of the most common toxic materials are zinc pennies, nickels, dimes and Monopoly game pieces which ferrets occasionally ingest. I have also seen hemolytic anemia in ferrets that had ingested uncured urethane caulk.
The gums and white portions of the eyes of ferrets with hemolytic anemia are often yellow (icteric) due to the presence of excessive destroyed hemoglobin products within the body (bilirubin).
Non-regenerative Anemias
The most common cause of non-regenerative anemia in ferrets is elevated blood estrogen levels in unsprayed female ferrets undergoing prolonged heat periods. Ferrets, like all mustella, must mate to complete their estrus cycle. If mating does not occur, the animals remain in proestrus – a time of elevated blood estrogen. This high blood estrogen suppresses red blood cell formation in the bone marrow. Injection of human chorionogonadotropin will occasionally allow the ferret to ovulate and complete its cycle. However, the best treatment is to spay the ferret before the anemia becomes severe or mate the animal. Non-regenerative anemia is also sometimes seen in the leukemias and adrenal cell tumors common in these pets.
Cancers: Many other 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 (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 the bone marrow. Also, 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.

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