Blastomycosis in Dogs
Dogs are more susceptible because their noses are closer to the soil. It is believed that blastomycosis is more rampant during the fall season. Sporting and hunting breeds are the most often seen with blasto because of their frequent exposure to soil in wet areas. Young adults are more affected, but possibly just because that is the age group most often seen in hunting or field trials and on training grounds. For an unknown reason, one study has found that male dogs are more likely to contract it. Another study found that, while female dogs may have better survival rates with therapy, they are more likely to suffer relapses than males.
Blastomycosis has also been reported in other animals, including the horse, cow, cat, bat, and lion.
Symptoms in Dogs
- skin lesions, or small draining ulcer(s) on the skin, like a small abscess - draining bloody or purulent (pus) material
- sudden blindness
- blood in the urine
- poor appetite
- shortness of breath
- fever that doesn't respond to antibiotics - 103 degrees or higher
- exercise intolerance
- enlarged lymph nodes
- eye problems: including redness, pain, swelling, excessive tearing, clouding of the corneas, and even blindness
- testicular inflammation
Dogs often acquire blastomycosis after breathing in the spores from the soil through their nose and into their lungs. The skin lesions occur if the fungus get into the skin through an existing wound or puncture. In the lungs, it causes a pulmonary (lung) infection. It then spreads through the bloodstream or lymphatic system from the lungs to the eyes, brain, bone, lymph nodes, urogenital system, skin, and subcutaneous tissues.
After exposure to Blastomycosis, it may be weeks or months before you dog is showing symptoms. If a dog only inhales a few spores and is healthy, it is possible for his immune system to eliminate the spores. However if the amount of spores is great, or if the dog is immune suppressed or fighting another disease they will have a greater chance of taking hold within the lungs. As the single-celled yeast they become in the lungs, they can multiple rapidly.
To diagnose Blastomycosis, you need to get a positive sample of the blasto yeast from a lymph node or draining skin lesion or possibly by doing a lung wash, and maybe by sampling material coughed up by the dog. It is very difficult to get a positive sample, and there are many false positives and negatives when trying to diagnoses blastomycosis. A chest x-ray will confirm the symptoms, but not definitively diagnose the condition. Chest x-rays often show a "fluffy snowstorm" appearance to the lungs, which are the fungal organisms and associated inflammation.
One informational site says that "About 65 percent of dogs diagnosed with blastomycosis do survive. Because the treatment is long, complicated, and expensive with the potential for serious side effects, some owners elect to euthanize affected pets. In treated dogs, survival rates are approximately 85 percent, with up to 25 percent suffering relapses. Dogs with brain or eye involvement have a worse prognosis, and dogs with poor liver or kidney function may not be able to tolerate the necessary medications that must be metabolized by these organs. If an eye is involved, it usually must be removed since eyes don't respond well to therapy and serve as a source of infection." (source). Personally, and unfortunately, all the stories I have heard about blastomycosis in the last week have involved the death of the dog.
The treatment drugs of choice are amphotericin B, Ketoconazole and Itraconazole. Treatment is very expensive, and all figures I have read this week report costs incurred over \$5000 Cdn. More information about these drugs for treatment, the use and side-effects can be found on this page
Even if the drug treatment is successful, it will not reverse any spinal or bone damage, or blindness. Even after treatment, the infection can remain dormant for many years and then reappear. However, after a year of remission without disease recurrence it is unlikely that your pet will have another occurrence of the disease.
There is no vaccine to protect your pet from blastomycosis. Avoidance of high-risk areas is the only thing you can do to lower your risk. Avoid areas of disturbed soil near water in areas where blastomycosis is common. Don't allow your dog to dig in soil that may contain the fungus. Knowledge of the symptoms and existence of this disease will be your weapon should your dog ever begin to develop the symptoms mentioned above.