What Does Low White Blood Cell Count Mean In Dogs?

Leukopenia is a drop in the number of circulating white blood cells (leukocytes). This makes a dog more susceptible to infections, as he has fewer white blood cells available to fight it off. Neutropenia is the most common type of leukopenia, which is a condition in which there are low numbers of neutrophils, the most abundant type of leukocyte. Leukopenia usually the result of an underlying cause, such as infection, cancer, or a genetic abnormality.

Your dog’s white blood cells are an important part of his immune system – his first line of defense against disease. As the number of leukocytes decrease, his risk of infection increases.

Neutrophils are the most numerous white blood cell in dogs. They are the first antibodies to respond to an infection, travelling quickly to the site and binding to the foreign bacteria or virus that is causing the problem. Neutrophils are short-lived cells, generated in large numbers by the bone marrow. A low number of neutrophils, called neutropenia, is the most common reason for leukopenia in dogs. Many acute or long-lasting infections can cause neutrophil numbers to drop because the cells are destroyed faster than the bone marrow is able to compensate. Autoimmune responses, genetic disorders found in some breeds, cancer, and drug toxicity can also cause neutropenia. While leukopenia is not a definitive diagnosis, analyzing the numbers and different types of blood cells that are present will help the veterinarian identify your dog’s disease.

Symptoms of Low White Blood Cell Count in Dogs

The most common sign of a low white blood cell count in dogs is an inability to fight off infections. Take your dog to the veterinarian if you notice signs of persistent or recurring infection.

– Fever
– Vomiting
– Diarrhea
– Lethargy
– Bleeding
– Pale coat and nose

Depending on the primary cause, neutropenia could be present with many different types of symptoms.

Types

Blood test results can show reduced numbers in the different types of white blood cells, which helps determine what kind of leukopenia your dog has:

Leukopenia – drop in the total number of white blood cells, usually due to neutropenia

Neutropenia – low numbers of neutrophils associated with infection, autoimmune response and genetic disorders. Neutropenia is the most common type of leukopenia.

Pancytopenia – an extreme form of neutropenia with a simultaneous reduction in red blood cells and platelets; often associated with bone marrow dysfunction or failure

Lymphopenia – low numbers of lymphocytes often associated a stress response that causes high levels of cortisol; doesn’t usually cause leukopenia unless neutropenia is also present

Eosinopenia –also indicates a stress response

Causes of Low White Blood Cell Count in Dogs

Many disorders can cause white blood cell numbers to drop in dogs.

– Prolonged or overwhelming infection
– Parvovirus
– Infectious hepatitis
– Coronavirus
– Cancers of the bone marrow
– Sepsis
 – Chemotherapy drugs
– Some antibiotics (trimethoprim sulfamethoxazole)
– Dipyrone (fever medication)
– Estrogen replacement therapy
– Autoimmune diseases
– Ehrlichia (infection by a tick-borne parasite)
 – Genetic disorders, particularly in grey collies (cyclic hematopoiesis or canine cyclic neutropenia and Giant Schnauzers (malabsorption of vitamin B)

Diagnosis of Low White Blood Cell Count in Dogs

A complete blood cell count will include a leukogram, which will measure the number of each type of white blood cell. It will also measure red blood cells and platelets. If your dog’s bone marrow is affected, the blood cell count may reveal low levels or red blood cells and platelets as well, since the stem cells in the bone marrow may be unable to generate any type of blood cell.

Your vet may notice an inflammatory response, or “left shift,” which means that there are high numbers of immature neutrophils. This means that your dog may have had a very recent infection, or that he may have a severe systemic disease that is destroying the neutrophils faster than his bone marrow can create them. Your vet may note the severity of his neutropenia and other symptoms to determine the cause of his leukopenia.

Very low neutrophil numbers are usually a sign of parvovirus. Other infections will deplete your dog’s neutrophils, but not as severely.

If few immature cells are present, it could mean that your dog’s bone marrow is having an issue creating new cells. This could be caused by cancer, an auto-immune disorder, or drug toxicity.

Information such as your dog’s age, breed, vaccinations, potential exposure to infection, and past and present medications will help your vet make an accurate diagnosis. Your veterinarian may perform a full physical examination and take urine and possibly feces samples to get a better picture of your dog’s overall health.

Treatment of Low White Blood Cell Count in Dogs

Treatment will depend on what’s causing your dog’s leukopenia. A bacterial infection will call for antibiotics, which will also help support his immune system. No matter which type of leukopenia your dog has, his immune system will be weakened. Fluids, electrolytes, and other supportive treatment may be necessary for dogs with very severe infections.

If your vet doesn’t think that infection is the primary cause, immune suppressants, prednisone or another steroid may be given. Immune suppressants should not be given to dogs with severe infections as this will limit the body’s natural disease fighting response.

Cancerous conditions will be treated with chemotherapy, but this could also further deplete your dog’s white blood cell count. Antibiotics will likely be given at the same time to support your dog’s immune system.

Gray Collies with inherited neutropenia will rarely survive into adulthood as there is no treatment except to manage bacterial infection as much as possible. A bone marrow transplant could cure the condition, but this is a costly and risky procedure that is rarely done in dogs.

If the problem is due to another drug, the veterinarian will try to eliminate this drug or reduce the dosage.

Recovery of Low White Blood Cell Count in Dogs

Leukopenia can be the sign of many serious conditions that require lifelong management. Blood cancers may respond to chemotherapy, but full recovery is unlikely. Many other potential causes could require long-term medication and your dog will need to be monitored carefully for side effects or toxicity. If infection is the primary cause, your dog may make a full recovery, as long as he survives the initial disease.

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