Blastomycosis in Dogs


Blastomycosis (also known as “Blasto”) is a fungal infection in dogs caused by Blastomyces fungi. This type of fungus tends to live in the soil and decaying organic matter (e.g. rotting logs and vegetation). Blastomycosis occurs most often in the mid-Atlantic states of North America, especially the Ohio, Mississippi, and Missouri river valley regions. Dogs become infected after breathing in Blastomyces fungal spores in the environment. Those infected can become extremely ill, commonly with respiratory disease, and many will die without treatment.

Blastomycosis fungal infection in dogs is common. Humans can also become infected in the same manner as dogs. Disease is not spread from animal to animal and is not contagious. Blastomycosis infections in other animals (e.g. cats) are rare.

Symptoms and Identification

Respiratory disease is typical. Symptoms include coughing, trouble breathing, and congestion. Blastomycosis can affect many other areas of the body including the eyes (e.g. blindness, squinting, eye redness), skin (e.g. open, oozing sores; hard bumps under the skin), bones (e.g. leg pain, trouble walking), and lymph nodes (e.g. large swellings under the chin and in front of the shoulders).

If blastomycosis is suspected, a veterinarian will need to perform a thorough physical examination. This will include looking at the eyes, in the mouth, checking all areas of the skin, and listening to the heart and lungs with a stethoscope. Chest x-rays are commonly performed as blastomycosis is frequently found in the lungs. Blood work and urine testing can be used to assess organ dysfunction and sometimes for diagnosis; however, most cases of blastomycosis must be diagnosed by microscopic examination of portions of affected tissues (e.g. biopsies of oozing skin wounds or swellings under the skin).

Affected Breeds

Any breed of dog can develop blastomycosis. Large breed dogs seem to be more commonly infected. This may be because large breed dogs are more often used for hunting or working in the woods and in areas that have a higher incidence of Blastomyces fungus than small breed dogs. Any age or sex of dog can be infected.


Treatment of blastomycosis requires long-term antifungal medications (i.e. average 2-6 months of therapy). Itraconazole or fluconazole are most commonly used. Some dogs may need to be hospitalized initially to help control some of their more severe symptoms. Some dogs will respond to medications, but relapse after stopping the antifungals, developing symptoms again. Some of the initial symptoms (e.g. blindness) may be permanent. Fortunately, overall prognosis (i.e. survival with a good quality of life) is very good if the pet responds to treatment.

Veterinary Cost

Blastomycosis is an expensive disease to diagnose and treat. Lab work, x-rays, and biopsy can cost anywhere between $500-$1500. Long-term antifungal medication can also be expensive. The monthly cost, depending on the dog’s size and dose, may be between $150-$750.


No vaccines are currently available to prevent blastomycosis. Starting treatment as soon as possible may help prevent severe disease, so prompt examination and care is very important.


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