Canine Blastomycosis

Canine blastomycosis is a fungal disease that can affect dogs, people, and sometimes cats. It can cause significant pulmonary disease such as pneumonia. This page looks at the symptoms, cause, and treatment of blastomycosis in dogs.

Blastomycosis is a systemic fungal disease caused by the fungus Blastomyces dermatitidis.

The fungus is found as a mold in the soil or at room temperatures. Particularly, it can usually be found in organic moist debris, enriched with bird droppings (in particular, those of pigeons), rotting in the shade. In tissues or at body temperatures, the fungus exists as a yeast.

In the USA, blastomycosis usually occurs the Great Lakes region, along the eastern seaboard, and the Mississippi, Ohio, and Missouri River valleys. People and dogs can be infected by blastomycosis but dogs are considerably more prone to the disease.

Canine blastomycosis occurs when a dog inhales infected spores. All dogs may contract blastomycosis but certain populations are at greater risk. For example, for reasons unknown, male dogs are more prone to blastomycosis than females. In addition, young adult hunting and sporting breeds are understandably at higher risk of contracting the disease since they are in more constant contact with soil in wet areas than other non-hunting breeds.

Canine Blastomycosis Symptoms

As mentioned above, a dog gets infected by inhaling infected spores of the fungus. Once the spores enter into the dog's lungs, they transform into large thick-walled budding yeast which continues to multiply within the lung and other tissues. Most cases of acute blastomycosis in dogs involve the respiratory system and cause significant pulmonary disease, such as pneumonia. Thus, a dog with blastomycosis that affects his lungs may show symptoms like:

Persistent chronic cough
Shortness of breath
Difficulty breathing
Fever (103°F or higher)
Appetite loss
Weight loss
Depression
Weakness and lethargy

The yeast also tends to spread via the bloodstream or lymphatic system from the lungs to other parts of the dog's body, affecting the skin, brain, eyes, and joints. Depending on the sites of the body affected, the dog may show symptoms such as:

Eye infection
Sudden blindness (if inner structures of the eyes are affected)
Skin lesions or pus-filled abscesses that are difficult to heal
Swollen lymph nodes
Lameness
Reluctant to walk or play
Unsteady gait
Head pressing against a wall or other hard surfaces
Loss of coordination

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Canine Blastomycosis Diagnosis

The most efficient way to make a diagnosis is by identifying the fungus in the fluids taken from the lungs.

Although not diagnostic by themselves, chest x-rays, a complete blood count (CBC), and urine tests are important tests because they assist in the diagnosis by detecting breakdown products of the fungus (antigens).

Sometimes, in cases that are difficult to diagnose, biopsy and culture may be needed.

Canine Blastomycosis Treatment

Conventional treatment of blastomycosis is the use of antifungal medication.

A combination of amphotericin B and one of the imidazoles (such as itraconazole, ketoconazole, fluconazole) seems to provide the most effective treatment. (However, amphotericin B is potentially damaging to the kidneys.)

Treatment may take months depending on the severity of the disease and some dogs may relapse months or even years later.

Fido Says: Although people cannot get blastomycosis directly from their dogs, they may acquire the fungus from their dog patients' bandages and/or bedding. Therefore, if you are taking care of your dog who is infected with the disease, be sure to wear latex gloves and take extra precautions!