Red blood cells (RBC) work to deliver oxygen to the dog’s tissues. This is done when the blood cells pick up oxygen in the lungs and release it to the body’s cells when the RBCs squeeze through the capillaries. This “pick up” is performed by the iron-containing hemoglobin (also spelled haemoglobin) biomolecule. The hemoglobin in the red blood cells then picks up the resulting carbon dioxide and delivers it to the lungs so that it may be expelled via exhalation.
Anemia (meaning “lack of blood” from the Greek) can mean that the hemoglobin molecules in the blood fail to bind to oxygen, or that there is an actual deficiency of red blood cells or hemoglobin molecules themselves. Because all cells and processes in the body depend upon oxygen for proper function, anemia can cause severe consequences ranging from mild illness to death.
Anemia is the most common blood disorder suffered by dogs.
There are three types of anemia in dogs: hemolytic anemia (caused by the destruction of red blood cells), hemorrhagic or iron-deficiency anemia (caused by blood loss), and aplastic anemia (caused by the insufficient production of red blood cells).
Hemolytic anemia occurs when red blood cells have an unusually short life-span, or where the cells are destroyed through immune or non-immune conditions. Autoimmune hemolytic anemia causes the immune system to view the red blood cells as foreign invaders and attack the cells. Non-immune hemolytic anemia may be caused by hereditary diseases, red blood cell parasites, low phosphorus levels, toxins, or hereditary enzyme or erythrocyte defects.
Hemorrhagic anemia occurs when the dog suffers a loss of blood through sudden or chronic blood loss. Sudden blood loss may be caused by surgery, trauma, or other bleeding disorder. Slower blood loss may be caused by external parasites like fleas or ticks, cancer, internal parasites, or ulcers.
Aplastic anemia may be caused by several different disorders that affect red blood cell production in the marrow. Anything that affects production of erythrocytes, like chronic kidney failure or tumours within the bone marrow, will do this. Exposure to toxins or radiation, certain drugs (sulfa drugs, phenylbutazone, estrogen, chemotherapeutic agents), or infections by Ehrlichia or parvovirus can disrupt red blood cell production.
There is no way to prevent anemia. Things you can do to reduce the likelihood of your dog developing anemia include keeping your dog safe to prevent trauma and the resulting blood loss, and monitoring red blood cell count when the dog is on certain medications or when ill. Follow good parasite control protocol if you live in areas where ticks and fleas are a concern. Immediate treatment of the underlying cause may prevent the disorder from becoming too serious.
Depending on whether the anemia is acute (comes on suddenly) or chronic (comes on slowly), owners may notice one or more symptoms. Symptoms of anemia may include bloody stools, lethargy, fever, weakness, lack of appetite, abdominal distension, difficulty breathing, depression, exercise intolerance, collapse, bounding pulse, pale mucous membranes, rapid and shallow breathing, elevated heart rate, and respiratory distress. When a dog displays more than one of these signs, anemia should be seriously considered.
If the dog is infested with fleas and shows one or more of these symptoms, anemia is a real possibility. Remember that not all dogs infested show signs of itchiness or irritation; check your dog frequently for flea dirt and live fleas. If your dog has flea dirt but you don’t see fleas, you can safely assume it has an infestation.
Dogs at Risk
Dogs of any breed and gender may suffer from anemia. Hemolytic anemia is seen more in Cocker Spaniels, Basenjis, English Springer Spaniels, West Highland White Terriers, Beagles, Dachshunds, Toy Eskimos, Cairn Terriers, and Miniature Poodles. Pit Bull Terriers and Greyhounds may be more likely to develop anemia when exposed to infectious agents. Any dog with gastrointestinal ulcers or heavy parasite loads could develop blood loss anemia.
Testing and Diagnosis
This blood disorder itself is not difficult to diagnose. The vet will do a detailed history and exam, and will draw blood to check for packed cell volume, complete blood count, and a serum biochemistry panel. He or she may order a urinalysis, and look at a smear of blood under a microscope to check the structure of the dog’s red blood cells. The vet may perform a buccal mucosal bleeding time test to check for clotting ability, a fecal analysis to check for occult blood loss, and a coagulation panel. Separate testing for the blood-borne parasite Ehrlicia canis may be done if it is suspected.
The above-mentioned tests will show red blood cell quality or quantity abnormalities. Although this may allow the vet to determine anemia is present, it does not identify the cause. Further investigation and advanced diagnostic testing like core bone marrow biopsy, bone marrow aspiration, abdominocentesis, abdominal x-rays, ultrasound, endoscopy, DNA tests, and chest films can help provide a clearer picture of the underlying cause. Each incidence will be determined on a case-by-case basis since the causes are so variable. Your vet will determine which diagnostic tools will best suit the situation.
Treatment and Prognosis
Goals for treatment include blood replacement, cessation of bleeding, and restoration of blood cell numbers. The underlying cause must be determined and treated, and supportive care must be provided throughout the entire process.
Dogs who suffer from traumatic blood loss may receive blood transfusions or intravenous fluid therapy to replace the lost volume. Bone marrow transplants are also an option. Dogs whose kidneys fail to produce erythropoietin may receive injections. Oral iron supplements are indicated for these patients. Dogs that have immune autolytic anemia may be treated with immunosuppressive drugs. Vitamin K1 may be prescribed for coagulation disorders. Dogs with internal parasites may be treated with de-wormers. Dogs with mineral imbalances should be treated appropriately (potassium phosphate, ferrous sulfate). Surgical intervention for dogs with trauma or tumours may be necessary.
Prognosis is usually good, as long as the anemia is detected and treated early enough to prevent organ failure. Once the originating cause is diagnosed and treated, the dog must be carefully monitored to ensure it returns to good health. Cases of chronic aplastic anemia can be difficult to resolve and usually takes months. Acute-onset aplastic anemia may be cured in as little as three to four weeks. Blood loss anemia has a good prognosis once the bleeding is stopped and volume is replaced. Younger dogs usually have a better prognosis. Unfortunately, cancer that causes anemia has may have a grave prognosis.
Dogs with ulcers should be treated to reduce stomach acid and their diet should be altered to allow the stomach to heal. Sucralfate, an oral medication, forms protective webbing over the ulcers and allows them to heal. Antibiotics or antiseptic mouthwashes may help heal secondary bacterial infections.