Blastomycosis - Bruiser's Silent Killer

Individuals and dogs that spend much of their time in the woods, swamps, or near water have a greater risk of infection from Blastomycosis.

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When Katie Thoele decided to take her six-year-old Miniature Pinscher Bruiser for a weekend of hiking in Wisconsin, she never anticipated the dangers lurking while Bruiser enjoyed the outdoors. Bruiser spent the weekend doing what he loved most— playing by the water, chasing chipmunks, and laying in the sunshine. It wasn’t until two weeks later when Bruiser started showing physical symptoms of illness, and four days later he died due to respiratory failure. Bruiser gained his wings July 9, 2010, after being taken by the disease known as Blastomycosis.

What is Blastomycosis?

Blastomycosis is a serious systemic fungal disease. It is caused by the fungus Blastomyces dermatitis that grows near water such as lakes, streams, beaver dams and other habits where soil is moist, acidic, and rich in decaying foliage. Most blastomyces spores will die unless the conditions are ideal for the fungus to survive. This explains why blastomyces are found in small pockets instead of being widespread, often making it difficult to find in the environment.

Who is at risk?

While humans can often become infected, dogs are 10 times more likely to develop the disease. Although it primarily infects dogs, humans and cats, it has also been reported in a wide variety of animals such as horses, ferrets, deer, wolves, African lions, bottlenosed dolphins, and sea lions. Blastomycosis is generally limited to North America, and most cases have occurred in Mississippi, Missouri, Tennessee, and Ohio River basins. Individuals and dogs that spend much of their time in the woods, swamps, or near water have a greater risk of infection. One study in Wisconsin has shown that 95% of infected dogs live within 400 yards of a body of water. Sporting and hunting dogs are therefore more commonly infected because of their frequent exposure to the soil and wet areas. When the ground where the fungus lives is disturbed, the infectious spores found in the soil are released into the air. Dogs often acquire infection by inhaling the spores through their nose which then travel down into the lungs where it induces a respiratory infection.

Clinical Findings & Symptoms:

When the respiratory defenses are overwhelmed, the disease spreads through the bloodstream from the lungs to other organs throughout the body to involve the eyes, brain, bones, lymph nodes, skin, and tissues just beneath the skin. According to Merck Veterinary Manual signs of pulmonary involvement are seen in up to 85% of affected dogs. Lymph node and skin involvement are reported in about 50% of affected dogs. Signs of ocular blastomycosis are seen in 30-50% of affected dogs and can include blindness, glaucoma and retinal detachment. Lameness associated with severe paronychia occurs in about 25% of affected dogs. Involvement in the central nervous system (CNS) is uncommon, occurring in

After exposure, some dogs may be infected but not show clinical signs for weeks or even months, and if left untreated can be fatal. The clinical symptoms of blastomycosis may vary with organ involvement which can include coughing, skin lesions, anorexia, depression, fever, weight loss, shortness of breath, exercise intolerance, enlarged lymph nodes, eye disease, or lameness.


The most common choice of treatment used for infected dogs and cats, is the antifungal drug Itraconzole. For aggressive cases, especially those with evidence of hypoxemia, combination treatment with Amphotericin B and Itraconzole is recommended under close veterinary care. Itraconzole should be given daily for a minimum of two months and continued until the disease is no longer noticeable. In treated dogs, clinical cure can be expected in ~70% of the dogs, with ~20% suffering relapses months to a year after treatment. Prognosis is best for dogs with mild or no lung disease, but is poorest for those with CNS involvement.

Although Bruiser struggled with some unrelated medical issues throughout his life, blastomycosis became his silent killer. The infection hid in his system two weeks before symptoms were apparent. He was quickly diagnosed and treated with medication, but it proved to be too late and his body couldn’t handle the recovery. After losing her best friend it has been Katie’s mission to inform pet owners and lovers of the risks to help save the lives of other beloved companions everywhere.


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