Description

Blastomycosis is a fungal disease caused by Blastomyces dermatitidis that affects both dogs and humans. Dogs are ten times more likely to be infected than humans. The disease in dogs can affect the eyes, brain, lungs, skin, or bones.

Signs and symptoms

Blastomycosis can present in one of the following ways:

• a flu-like illness with fever, chills, myalgia, headache, and a nonproductive cough which resolves within days.
• an acute illness resembling bacterial pneumonia, with symptoms of high fever, chills, a productive cough, and pleuritic chest pain.
• a chronic illness that mimics tuberculosis or lung cancer, with symptoms of low-grade fever, a productive cough, night sweats, and weight loss.
• a fast, progressive, and severe disease that manifests as ARDS, with fever, shortness of breath, tachypnea, hypoxemia, and diffuse pulmonary infiltrates.
• skin lesions, usually asymptomatic, appear as ulcerated lesions with small pustules at the margins
• bone lytic lesions can cause bone or joint pain.
• prostatitis may be asymptomatic or may cause pain on urinating.
• laryngeal involvement causes hoarseness.

Cause

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.

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.

Treatment

Itraconazole given orally is the treatment of choice for most forms of the disease. Ketoconazole may also be used. Cure rates are high, and the treatment over a period of months is usually well tolerated. Amphotericin B is considerably more toxic, and is usually reserved for immunocompromised patients who are critically ill and those with central nervous system disease. Fluconazole has also been tested on patients in Canada.

Prognosis

Mortality rate in treated cases

• 0-2% in treated cases among immunocompetent patients
• 29% in immunocompromised patients
• 40% in the subgroup of patients with AIDS
• 68% in patients presenting as acute respiratory distress syndrome (ARDS)

Wikipedia and GNU

The content of this entry is from the Wikipedia article "Blastomycosis" licensed under the GNU Free Documentation License.