What Is Anemia in Dogs?
Anemia presents a common clinical challenge characterized by a reduction in red blood cells (RBCs), which are vital for transporting oxygen throughout the body. Dogs manifest anemia through various symptoms, which vary depending on the cause, severity, and duration of the condition. As anemia progresses, dogs may exhibit signs of shock and dysfunction in their cardiovascular and respiratory systems, which can be life-threatening.
There are generally three mechanisms through which a dog can become anemic:
- RBC loss: Normal RBC production occurs in the bone marrow, but RBCs are lost or seep out of blood vessels.
- RBC destruction: The body prematurely destroys RBCs.
- Decreased RBC production: Insufficient RBCs are produced by the bone marrow.
Furthermore, anemia can be categorized based on the bone marrow’s responsiveness:
- Regenerative anemia: The bone marrow appropriately responds to the reduced RBC count by generating new RBCs.
- Nonregenerative anemia: Insufficient RBC production occurs in the bone marrow.
It is crucial to seek immediate veterinary attention if your pet displays symptoms such as pale gums, difficulty breathing, active bleeding, or unusual bruising.
Symptoms
The clinical manifestations of anemia in dogs vary depending on the cause, severity, and duration of the condition. Dogs with chronic illnesses may exhibit nonspecific symptoms or may not display any clinical signs until the anemia becomes severe. These dogs can adapt to lower red blood cell (RBC) counts over an extended period, whereas those experiencing acute blood loss may immediately demonstrate distress and illness. Common symptoms of anemia in dogs include:
- Weakness
- Lethargy
- Reduced appetite
- Pica (consumption of non-food items)
- Weight loss
- Paleness of the mucous membranes (gums)
- Elevated heart rate
- Increased respiratory (breathing) rate
- Difficulty breathing
- Collapse
- Presence of small or large bruises across the body (petechiae and ecchymoses)
- Jaundice (accumulation of yellow pigment in the blood and tissues)
- Blood loss from the nose, mouth, or urogenital or gastrointestinal systems
Causes
Anemia can affect dogs of all breeds, ages, and genders. Certain breeds have a predisposition to a specific type of anemia known as Immune-mediated Hemolytic Anemia (IMHA). These breeds include:
- American Cocker Spaniel
- Miniature Schnauzer
- Collie
- Doberman Pinscher
- English Springer Spaniel
- Poodle
- Bichon Frise
- Miniature Pinscher
- Old English Sheepdog
- Maltese
Acute blood loss can result from trauma, surgery, coagulopathies (impaired clotting), rodenticide toxicity, a ruptured spleen, and hemorrhagic cancers such as hemangiosarcoma. Chronic blood loss may also lead to anemia due to conditions such as long-term gastrointestinal ulcers, parasites (such as hookworms and fleas), tumors, nutritional deficiencies, and certain medications.
Red blood cell (RBC) destruction occurs when normal RBCs are prematurely and improperly removed from the system. Normally, RBCs have a lifespan of around 110 to 115 days in dogs and are eliminated by the spleen, liver, or bone marrow as they age.
Common examples of this type of anemia include:
- Immune-mediated Hemolytic Anemia (IMHA), which occurs when the immune system attacks the red blood cells. This can be triggered by drugs, infections, cancers, or inflammatory diseases, or it may have no clear cause.
- RBC parasites, such as babesia, can induce anemia.
- Oxidative stress leads to anemia and can be caused by onion/garlic toxicities, acetaminophen and benzocaine toxicities, and zinc toxicosis. Oxidative stress causes normal oxygen-carrying hemoglobin to convert to methemoglobin, which cannot effectively bind or deliver oxygen to cells.
- Mechanical damage can occur to RBCs in conditions like heartworm disease, vasculitis, cardiac disease, liver disease, disseminated intravascular coagulation (DIC), and certain cancers.
- Other causes of RBC destruction include certain infections, incompatible blood transfusions, genetic RBC abnormalities and disorders, diabetic ketoacidosis, propofol administration, and hypophosphatemia (low phosphorus).
Decreased RBC production occurs when the bone marrow fails to generate enough RBCs. This type of anemia is inherently nonregenerative. Factors affecting the body’s ability to produce RBCs include:
- Chronic inflammatory diseases
- Chronic kidney disease
- Hypothyroidism
- Addison’s disease
- Immune conditions
- Infections
- Cancer
- Bone marrow suppression caused by infectious agents, drugs, and toxicities such as:
- Infectious agents—Parvovirus, babesia, ehrlichia
- Drugs—Chemotherapy agents, lead, methimazole, phenobarbital, fenbendazole, TMS, albendazole
Diagnosis
Veterinarians often suspect anemia based on a patient’s medical history and findings from a clinical examination, particularly if the dog exhibits pale gums, bruising, or evident abdominal tumors. However, the definitive diagnosis of anemia requires blood tests to assess the red blood cell (RBC) count and other RBC characteristics such as size, shape, and color, which aid in determining the severity, chronicity, or underlying cause of the anemia.
Diagnostic procedures include:
- Complete blood count (CBC): This comprehensive test examines various RBC factors, assisting veterinarians in devising the most effective treatment plan for anemia.
- PCV/TS: This quick and straightforward diagnostic tool measures the packed cell volume, providing another means to monitor RBC levels.
- Reticulocyte count: This test identifies increased numbers of young RBCs, indicating a regenerative response.
- Biochemistry and urinalysis: These tests evaluate organ function and other parameters that may contribute to anemia.
- Slide agglutination test: This basic blood test detects abnormal clumping of RBCs in cases of Immune-mediated Hemolytic Anemia (IMHA).
- Cytology or blood smear: This examination allows for the microscopic evaluation of RBCs, aiding in identifying the cause and the bone marrow’s response to anemia.
- Bone marrow evaluation: This procedure involves examining the bone marrow for signs of cancer, regeneration, or infectious agents, assisting in determining the underlying cause of anemia.
- Imaging: Radiographs and ultrasound scans can help identify underlying causes of anemia, such as bleeding tumors.
- Other tests: Serology for infectious agents, fecal tests, coagulation profiles, endocrine testing, organ function tests, and tumor biopsies are additional diagnostic tools used for dogs presenting with anemia.
Treatment
The primary objective in treating dogs with anemia is to address the underlying condition. Treatment approaches vary depending on the chronicity and severity of the disease. Common methods for treating anemia include:
- Surgical intervention to remove bleeding masses or repair traumatic wounds.
- Vitamin K therapy to counteract rodenticide poisoning.
- Administration of antiparasitic drugs to combat internal parasites.
- Prescribing antibiotics to address tick-borne or other infectious agents.
- Discontinuation of medications causing adverse effects.
- Use of steroids or immunosuppressive medications to manage autoimmune diseases.
- Administration of blood products to replenish RBCs and other vital blood components.
- Provision of supportive care, including intravenous fluids.
Living and Management
Veterinarians commonly utilize serial complete blood count and/or PCV/TS testing to monitor the dog’s response to treatment, while also observing for any underlying diseases that may contribute to the anemia. Typically, if the underlying condition is effectively treated, it may take several weeks for the dog’s blood levels to normalize, although clinical improvement is often noticeable within a few days.
These dogs may necessitate ongoing medical management and regular monitoring to detect any recurrence. While certain causes of anemia such as trauma, infectious agents, or parasites can be resolved, severe cases of anemia may be too advanced for treatment, even with aggressive therapy.
Management strategies vary depending on the underlying factor and may be required for the duration of the dog’s life. Dogs diagnosed with Immune-mediated Hemolytic Anemia (IMHA) are particularly susceptible to relapses. Caution should be exercised when administering medications or vaccines to these dogs to minimize the risk of recurrence.