This systemic fungal disease occurs along the eastern seaboard, in the Great Lakes region, and the Mississippi, Ohio, and Missouri River valleys. The fungus is associated with moist, rotting organic debris protected from sunlight and enriched with bird droppings, particularly those of pigeons. The disease is acquired by inhaling infected spores. Dogs are considerably more susceptible to blastomycosis than are humans.
Most cases of acute canine blastomycosis involve the respiratory system and cause bronchopneumonia. About 40 percent of cases involve the eyes and skin, producing signs similar to those of cryptococcosis. Weight loss and lameness may also be noted.
Microscopic identification of organisms in transtracheal washings or in fluid aspirated from infected tissues is the most efficient way to make the diagnosis. In difficult cases, biopsy and culture may be needed. Serologic tests also are available.
Treatment: A combination of amphotericin B and one of the imidazoles appears to offer the best chance of successful treatment (as described for Histoplasmosis). Months of treatment are required, and some dogs may relapse months to years later.
Public health considerations: Although the hazard to human health is minimal, humans can acquire the fungus from infected bandages and bedding. Use rubber gloves and take hygienic precautions when handling an infected dog.