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Valley Fever (cont.)

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What causes valley fever (coccidioidomycosis)?

Coccidioidomycosis is caused by two species of fungi, Coccidioides immitis and Coccidioides posadasii. Both are dimorphic (having mycelial and spore phases when viewed microscopically) and almost always are acquired through the respiratory tract by inhalation. When viewed microscopically, the mycelial form found in the soil has arthroconidia (barrel-shaped asexual spores) attached to non-spore-forming rectangular mycelium cells, usually alternating in a line. Once the arthroconidia are inhaled, the fungus develops into 30-60 micron diameter structures called spherules that are filled with 3-5 micron diameter endospores. The large spherules then release the endospores that continue the infection; microscopic identification of these endospores in pus or tissue confirms the diagnosis.

What are the symptoms and signs of valley fever (coccidioidomycosis)?

About 60% of all infected people (without immunosuppression) have no symptoms and do not seek medical care. About 30%-35% of people who develop symptoms have flu-like symptoms (fever, cough, malaise, and chills) that resolve over about two to six weeks without treatment. Some may develop additional symptoms such as shortness of breath, night sweats, headaches, sputum production, and joint and muscle pains (symptoms resembling pneumonia). Women, more often than men, may develop erythema nodosum (reddish, painful, tender lumps, usually on the legs) or erythema multiforme (an allergic reaction similar to erythema nodosum in multiple body sites with rash). The combination of fever, erythema nodosum, and migratory joint pains are often referred to as "desert rheumatism." Usually these symptoms resolve in about two to six weeks.

Chronic coccidioidomycosis occurs in about 8% of patients and is characterized by the above symptoms but may spread from the lungs to other parts of the body. People develop lung cavities that may disappear in about two years or become calcified.

Progressive pulmonary coccidioidomycosis includes the above symptoms but progresses to lung volume loss, fibrosis (scarring), and inflammation, considered serious complications of the disease.

Disseminated coccidioidomycosis (about 1% of cases) can be characterized by the above symptoms, but they may occur over weeks to years. The fungi may be found in any organ system but are most frequently seen in the skin, meninges, and bones. In a few individuals, the disease is rapidly fatal. Disseminated disease occurs most often in immunosuppressed individuals, males, and pregnant females.

Other mammals, like dogs, can become infected. As many as 28% of dogs by the age of 2 years may have had the disease, with about 6% showing symptoms of cough, shortness of breath, decreased appetite, and listlessness. The animals are not contagious to each other or humans, but like in some humans, the disease may progress.

Medically Reviewed by a Doctor on 3/18/2016


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