Blastomycosis in Dogs
By: Dr. Rosanna Marsalla
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Pet Lovers
Other medical problems can cause symptoms similar to those encountered in pets with blastomycosis. Your vet will exclude these conditions as necessary before establishing a diagnosis of blastomycosis:
Bacterial pneumonia
Brucellosis
Histoplasmosis
Coccidioidomycosis
Cryptococcosis
Nocardiosis
Actinomcyosis
Rocky Mountain Spotted Fever
Ehrlichiosis
Neoplasia (cancer)
Lymphosarcoma
Primary lung tumor
Tumor elsewhere in the body that has spread (metastasized) to the lungs
Heart failure
Heartworm disease
Systemic immune-mediated disease such as systemic lupus erythematosus
Nodular panniculitis
Lymphomatoid granulomatosis
Eosinophilic lung disease
Blastomycosis is a systemic disease caused by a fungus (Blastomyces dermatidis) present in the soil of certain geographic regions like Mississippi, Missouri and Ohio River Valley). Dogs and people are most commonly infected.
Infection occurs by inhalation of spores from the "mycelial" form of the organism found in the environment, especially moist soil. After the organism becomes established in the lung, dissemination throughout the body occurs. Blastomycosis is endemic in the Mississippi, Missouri and Ohio River valleys.
Young male dogs, especially hunting dogs, are at increased risk presumably because of increased contact with contaminated soil. The yeast form of the organism found in infected body tissues is not contagious, and thus the disease is not readily transmissible between animals or from animals to people.
The prognosis depends on the extent and severity of lung involvement. In dogs, blastomycosis affects the lungs (80 percent of cases), eyes (40 percent of cases), skin (20 to 40 percent of cases), and bones (30 percent of cases).
Most affected animals have systemic symptoms such as fever, lethargy, loss of appetite, and weight loss. Lung involvement leads to respiratory symptoms such as exercise intolerance, cough, and difficulty breathing. The animal's peripheral lymph nodes often are enlarged. These are found under the neck, in the shoulder region and behind the knee. Bone involvement may occur and result in lameness.
Infection of the urogenital tract, for example the prostate gland in male dogs, occasionally may occur and cause clinical symptoms like blood in the urine or difficult urinations. Nervous system involvement may cause seizures, uncoordination, head tilt, and other symptoms.
Eye involvement can lead to squinting due to pain and light sensitivity. Involvement of the retina may lead to blindness. Involvement of the iris of the eye may be complicated by glaucoma, which is high pressure within the eye. Draining nodules may be found in the skin, and microscopic examination of this material often discloses the organism and yields a diagnosis.
