What Is Blastomycosis?
Blastomycosis is a fungal infection caused by Blastomyces organisms that live in certain soils and decaying organic matter. In the United States it is classically associated with river valleys and parts of the Midwest, South-Central, and Great Lakes regions — though travel and relocating dogs mean cases can appear outside “textbook” maps.
Dogs inhale fungal spores from the environment. The infection often starts in the lungs and can spread (disseminate) to skin, eyes, bones, lymph nodes, and other organs. Cats can be infected but are discussed less often than dogs in US clinics. Blastomycosis is not considered a routine contagious pet-to-pet or pet-to-person household disease the way a respiratory virus might be; the shared risk is usually the outdoor environment.
Why it matters
Blastomycosis can mimic bacterial pneumonia, cancer, or “just a cough.” Delayed recognition means more organ involvement. Dogs that swim, dig, or roam wet wooded soil in endemic areas deserve a low threshold for fungal testing when lung or skin disease is unexplained.
Signs Owners Notice
- Cough, exercise intolerance, or labored breathing
- Fever, weight loss, and reduced appetite
- Skin nodules, draining tracts, or non-healing sores
- Eye problems (redness, cloudiness, vision changes)
- Lameness if bone is involved
- Enlarged lymph nodes
Some dogs look like they have a stubborn respiratory infection that does not fully respond to ordinary antibiotics. Any combination of lung signs plus skin or eye disease in an endemic-area dog should raise fungal suspicion.
Diagnosis and Treatment
Veterinarians use history (geography, digging, water exposure), exam, chest imaging, and sampling. Diagnosis may involve cytology or histopathology of skin/lung samples, antigen testing (urine/serum), and sometimes culture or PCR. Ruling out other causes of pneumonia, cancer, and foreign material is part of a thorough workup.
Treatment typically requires long courses of prescription antifungal medication under veterinary supervision, plus supportive care for breathing comfort and nutrition. Eye or severe lung disease may need specialist input. Antifungals can have side effects — baseline and follow-up bloodwork matter. Stopping medication too early risks relapse; your vet will guide duration based on clinical response and monitoring tests.
Prevention and Everyday Tips
- You cannot sterilize endemic soil, but reducing high-risk digging in wet, disturbed earth during peak seasons may help some households.
- Tell your veterinarian about travel or relocation from river-valley or Great Lakes regions when respiratory or skin disease appears.
- Do not assume every cough is “kennel cough” if your dog worsens, loses weight, or develops skin lesions.
- Follow antifungal plans exactly and keep recheck appointments.
When to see a vet
Book promptly for persistent cough, breathing effort, unexplained weight loss, draining skin lesions, or sudden eye changes. Seek emergency care for blue/grey gums, collapse, or open-mouth breathing at rest.
Key Takeaways
- Blastomycosis is a soil-associated fungal disease that often starts in the lungs and can spread.
- Geography plus mixed respiratory/skin/eye signs should prompt fungal testing.
- Long antifungal courses and monitoring — not short antibiotic trials alone — are the usual path.
FAQ
Can people catch blastomycosis from their dog?
People usually get it from the same environmental spores, not from casual petting. Still, draining lesions should be handled with basic hygiene and veterinary guidance.
Is blastomycosis the same as valley fever?
No. Valley fever (coccidioidomycosis) is a different fungus with a different US geographic pattern, though both can cause serious lung disease.
Will my dog fully recover?
Many dogs improve with appropriate antifungal therapy, especially when diagnosed before widespread damage. Prognosis depends on organs involved and how early treatment starts.