Issue Description Infection occurs by inhalation of the fungus
from its natural soil habitat. Once inhaled in the lungs, they
multiply and may disseminate through the blood and lymphatics to other
organs, including the skin, bone, genitourinary tract, and brain. The
incubation period is 30 to 100 days, although infection can be
asymptomatic. Other Names N/A
Symptoms Dogs usually acquire blastomycosis by inhaling
the spores from the soil into the lungs, where it induces a
self-limiting pulmonary infection. Direct inoculation of the spores
into the skin through puncture wounds may cause local cutaneous
infection. By far, the most common form of blastomycosis seen by
veterinarians is the generalized or disseminated form, which spreads
via the bloodstream or lymphatic system from the lungs to involve the
eyes, brain, bone, lymph nodes, urogenital system, skin, and
The clinical signs of blastomycosis
may vary with the target organs affected and may include one or all of
the following: anorexia, depression, weight loss, fever (103 degrees
or higher) that doesn't respond to antibiotics, coughing, shortness of
breath, exercise intolerance, enlarged lymph nodes, eye disease, or
skin lesions that drain bloody or purulent material.
Diagnosis Once suspected, the diagnosis of blastomycosis
can usually be confirmed by demonstration of the characteristic broad
based budding organisms in sputum or tissues by KOH prep, cytology, or
histology. Tissue biopsy of skin or other organs may be required in
order to diagnose extra-pulmonary disease. Commercially available
urine antigen testing appears to be quite sensitive in suggesting the
diagnosis in cases where the organism is not readily detected. While
culture of the organism remains the definitive diagnostic standard,
its slow growing nature can lead to delays in treatment of up to
several weeks. However, sometimes blood and sputum cultures may not
detect blastomycosis; lung biopsy is another option, and results will
be shown promptly. 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.
Treatment Blastomycosis must be treated or it will
gradually lead to death. Treatment with the fungicidal drug
ketoconazole (Nizoral) taken orally is effective in about 75% of
patients. Amphotericin B (Fungizone) given intravenously is also very
effective, but it has more toxic side effects than ketoconazole.
Treatment with amphotericin B usually requires hospitalization, and
the patient may also receive other drugs to minimize the its side
Alternative treatment Alternative treatment for fungal infections
focuses on creating an internal environment where the fungus cannot
survive. This is accomplished by eating a diet low in dairy products,
sugars, including honey and fruit juice, and foods that contain yeast.
This is complemented by a diet consisting, in large part, of uncooked
and unprocessed foods. Supplements of vitamins C, E, A-plus, and B
complex may also be useful. Lactobacillus acidophilus and
Bifidobacterium will replenish the good bacteria in the intestines.
Some antifungal herbs, like garlic (Allium sativum), can be consumed
in relatively large doses and for an extended period of time in order
to increase effectiveness. A variety of antifungal herbs, such as
myrrh (Commiphora molmol), tea tree oil (Melaleuca spp.), citrus seed
extract, pau d'arco tea (Tabebuia impetiginosa), and garlic may also
be applied directly to the infected skin.
Prognosis Left untreated, blastomycosis gradually leads
to death. When treated, however, patients begin to improve within one
week and, with intensive treatment, may be cured within several weeks.
The highest rate of recovery is among patients who only have skin
lesions. Patients with the disseminated form of the disease are least
likely to be cured and and most likely to suffer a relapse.
Prevention Because the fungus that causes blastomycosis is
airborne and microscopic, the only form of prevention is to avoid
visiting areas where it is found in the soil.