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Cornell Feline Health Center

Supporting Cat Health with Information and Health Studies.


Blastomycosis is a fungal disease caused by the organism Blastomyces dermatitidis, and is more commonly found in dogs and people than in cats.  The fungus lives in soil and infection usually occurs through inhalation of infective spores, but it is also possible for direct inoculation through a skin wound to cause disease.  The disease in North America is found most commonly in the Mississippi, Missouri and Ohio river valleys, and near the Great Lakes, Manitoba and Ontario. Though the infective spores generally are found in soil near the water, blastomycosis has been documented in many indoor-only cats as well as cats with access to the outdoors.  

The most common clinical signs of feline blastomycosis include difficulty breathing, lethargy, weight loss, fever, cough, ocular changes, neurologic changes, or skin lesions. A urine and blood test for blastomycosis is available for dogs, but data is very limited in cats, so diagnosis in cats is generally made through visualization of fungal organisms in infected tissues under the microscope.  Treatment for feline blastomycosis is a prolonged course of oral antifungal medications. The prognosis for feline blastomycosis is guarded, but it is improving with the availability of newer antifungal medications.

Last updated 2021