Blastomycosis is diagnosed based on history, symptoms and then identification of the organism under a microscope or through a blood test. Smears from skin lesions or from aspirates of enlarged lymph nodes will contain identifiable blastomycosis organisms about half of the time. Collection of samples from the bronchi will also contain organisms in some instances. In cases where the disease is suspected but the organisms can not be found on microscopically, a blood test can be performed. While still not completely accurate, the agar-gel immunodiffusion test is the blood test that is most commonly used to identify blastomycosis.
Treatment is usually necessary for all dogs that become infected with blastomycosis.
Unlike some other fungal infections in which many animals are exposed and then recover from the infections on their own, with blastomycosis relatively few animals are exposed and infected, but those that are require treatment. There are several treatment options. The most common treatment is the oral administration of the antifungal drug Itraconazole . This drug usually needs to be given daily for 60 to 90 days. It is a human drug and can be very expensive, particularly for a large dog, but it is currently the safest and most effective way to treat blastomycosis.