Low White Blood Cell Count in Dogs

What Is Neutropenia in Dogs?

Neutrophils are white blood cells essential to a dog’s immune system. Produced in the bone marrow, these cells travel through the bloodstream to be first on the scene to sites of infection and inflammation. They will bind bacteria and viruses as well as signal for other white blood cells to come to the affected part of the body and help fight the infection.

Because neutrophils are the most common white blood cell, a significant decrease in neutrophil numbers (neutropenia) can leave dogs unable to resist infections. Low neutrophil counts can be due to decreased production in the bone marrow, increased use in the body, or abnormal destruction of the cells. Severe neutropenia in dogs is uncommon, but if it isn’t treated it can lead to serious health complications.

Low white blood cell count in dogs may be found on lab work in apparently healthy pups. Though these cases are not emergencies, they should be investigated and treated immediately if necessary to avoid potentially dangerous health issues. In other cases, severe lethargy and fever that require emergency care may be the first signs that something is wrong.

The survival of dogs with a low white blood cell count depends on how treatable the underlying cause is. Infections may respond easily to antibiotics with no chance for recurrence. Bone marrow abnormalities and cancers can be harder to manage and are more likely to be fatal.

Symptoms of Neutropenia in Dogs

Symptoms of low white blood cell count in dogs include:

• Decreased appetite

• Fever

• Lethargy/weakness

• Vomiting

• Diarrhea

• Bruising

• Pale gums

• Lameness

Causes of Neutropenia in Dogs

Low white blood cell (neutrophil) counts in dogs can have several different causes, including:

Infection

• Parvovirus

• Hepatitis

• Ehrlichiosis

• Fungal infections

• Sepsis

Medications

• Chemotherapy

• Estrogens

• Thyroid medication (methimazole)

• Seizure medication (phenobarbital)

• Antibiotics (sulfamethoxazole/trimethoprim)

Genetics

• Canine cyclic neutropenia (gray Collies)

• Hypovitaminosis B12 (Giant Schnauzers)

Autoimmune Disorders

• Immune-mediated neutropenia

Cancer

• Leukemia

• Multiple myeloma

How Veterinarians Diagnose Neutropenia in Dogs

Low white blood cell count in dogs is usually confirmed on a complete blood count (CBC) test. In dogs, an abnormal count is fewer than 3,000 cells per microliter.

A small decrease may be normal in some dogs and not a concern. If there are no symptoms, your dog’s breed, age, and medical history (including medications, parasite preventatives, and vaccines) will help your vet determine how serious the neutropenia is.

A physical exam, blood chemistry, urinalysis, X-rays, and abdominal ultrasound may help your vet determine the cause of neutropenia and how best to treat it. Your vet will often use these tests to look for infections or evidence of cancer.

Screening for blood and fecal parasites is important, especially in areas where tick-borne ehrlichiosis is common. Some cases may require a bone marrow biopsy to look for bone marrow cancers and abnormalities in how the body is producing these cells.

Treatment of Neutropenia in Dogs

Because the most common causes of low white blood cell count in dogs are infections and drug reactions, this syndrome is often treatable with antibiotics or discontinuation of the drug causing the issue. Complete remission can be expected.

Immune-mediated neutropenia also has a good prognosis, with most dogs returning to normal neutrophil counts within weeks after being administered immunosuppressive medications. Some dogs may require long-term medications for this disease.

Bone marrow cancers have a poorer prognosis, relying on chemotherapy for treatment, which can have its own bone marrow effects. While Giant Schnauzer neutropenia can usually be managed with lifelong vitamin B12 supplementation, Gray Collies born with cyclic neutropenia rarely live to be adults. 

Recovery and Management of Neutropenia in Dogs

Treatable causes of low white blood cell counts in dogs respond quickly to therapy, and most dogs will feel much better within weeks of receiving treatment.

Severe infections like parvovirus may require intensive hospitalization. In many cases, treatment can be discontinued once cell numbers have normalized, though some immune-mediated conditions may require lifelong medications.

With aggressive care, some bone marrow cancers can go into remission and affected dogs can have good quality of life for months to years. Prognosis highly depends on response to treatment.

Prevention of Neutropenia in Dogs

Routine wellness blood work can help identify low white blood cell counts in dogs before they feel ill. Dogs on long-term medications that can cause neutropenia should have blood counts performed at least annually to monitor for neutropenia.

Vaccines and parasite prevention (such as NexGard®, Bravecto®, Seresto®, or Simparica Trio™) can go a long way in preventing severe infections that cause neutropenia.

Prompt care of wounds and appropriate antibiotic use can help avoid sepsis and antibiotic-resistant infections.