Blastomycosis is a dangerous systemic disease caused by a fungal organism called Blastomyces dermatididis. This organism typically inhabits small pockets of sandy, acidic soil adjacent to bodies of water. Blastomyces dermatididis infects dogs and humans, although dogs are 10 times more likely to develop blastomycosis.
Blastomycosis has a "well-defined endemic area." Although its range continues to expand, it is generally found in Missouri, Mississippi, the Mid-Atlantic states, Ohio River valleys, and areas of Manitoba, Quebec, and Ontario.
Your dog becomes infected by inhaling Blastomyces dermatididis spores. The spores infect your dog's lungs and the infection spreads through his body, generally invading his subcutaneous tissues, lymph nodes, testes, skin, eyes, bones and brain.
Symptoms of blastomycosis include fever, coughing, depression, weight loss, appetite loss, difficulty breathing, eye problems, skin problems and lameness. Symptoms may appear to improve and then worsen again.
Diagnosis is made based on your dog's history, her symptoms and the confirmed presence of Blastomyces dermatididis. According to Pet Education, the fungus is typically identified through a tissue biopsy, antigen test, lesion smear or lymph node aspiration.
Infected dogs usually require months of closely monitored treatment with oral or intravenous antifungal medication. Due to severe loss of appetite, some dogs must be force-fed for 1 to 2 weeks.
Blastomycosis is commonly mistaken for other fungal infections, viral infections, Lyme disease or cancer. Unfortunate misdiagnoses have lead to delayed treatment or unnecessary euthanasia.