Blastomycosis in Dogs

The fungal respiratory infection blastomycosis can lead to death. The fungus is found mainly in warm, damp environments.


If you’re wondering what is blastomycosis in dogs, consider yourself lucky. Blastomycosis, sometimes referred to as simply “blasto,” is a nasty fungal infection that causes respiratory problems and can lead to death. If you haven’t heard of it, your dog hasn’t gotten this diagnosis.

Dogs (and humans!) can be infected when they accidentally breathe in fungal spores. The fungus is found in warm wet climates and resides in decaying matter, like leaves, and in soil. Once the spores are inhaled, they thrive in the warm, moist environment of the dog’s airways and lungs and begin to reproduce. In severe cases, the infection can spread to other organs in the body.

Blastomycosis Symptoms

Blastomycosis symptoms in dogs usually look like a respiratory infection and include coughing, difficulty breathing, weight loss, and lethargy. If other organ systems are infected, the dog might also have a fever, lameness, eye problems, or skin lesions. Blastomycosis is not contagious.

Blastomycosis Treatment

Blasto is treated with anti-fungal medications, as well as treatments targeted for any of the symptoms that your dog is experiencing. Dogs with mild respiratory signs generally have a good prognosis and are able to make a full recovery, but this disease can be fatal.

Blastomycosis Prevention

How to prevent blastomycosis in dogs? There is no sure-fire strategy, as we cannot see the fungal spores in the air or leaf litter. Avoiding areas where blasto is prevalent is the best strategy.

In the United States, blasto is most common in the midwestern, south-central, and southeastern states. The Mississippi, Missouri, Tennessee, and Ohio River basins, Great Lakes, and St. Laurence Seaway are the areas with the most cases reported. The fungus that causes it, Blastomyces dermatitidis, prefers a warm, moist environment.

If you live in one of these areas or have visited them with your dog, seek veterinary attention immediately if you notice any respiratory abnormalities – prompt treatment is the best way to protect your dog.

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Kate Basedow, LVT is a long-time dog enthusiast. She grew up training and showing dogs, and is active in a variety of dog sports. She earned her Bachelors Degree in English from Cornell University in 2013, and became a licensed veterinary technician in New York in 2017. She has been writing professionally about dogs for most of her life, and has earned multiple awards from the Dog Writers' Association of America. Kate currently has three dogs at home, as well as a cat, two zebra finches, and six ducks.