[Southern
Arizona VA Healthcare System] [University
of Arizona] [Campaign Arizona]
[The University of
Arizona Foundation ] [Arizona Health
Sciences Center]
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People working in certain occupations, such as construction, agricultural work, work involving disturbance of desert soils, and archaeology, have an increased risk of exposure and disease. The fungal spores of Coccidioides immitis are often found in abundance in the soil around rodent burrows, Indian ruins and burial grounds. In these settings, infections are more likely to be severe because of intensive exposure to a large number of spores. Many infections, however, occur in persons without occupational risks. Exposure to wind-storms or recently disrupted soils may increase the chances of infection. Valley Fever infections are more likely to occur during certain seasons. In Arizona, the highest prevalence of infections occurs June through July and from October through November. In California, the risk of infection is highest from June through November, without the late summer break. Many domestic and native animals are susceptible to the disease, including dogs, horses, cattle, sheep, burros, coyotes, rodents, bats and snakes. Dogs are especially susceptible and often need long-term therapy with antifungal medication.
Most cases of Valley Fever are very mild. It is thought that over 60% of infected people have either no symptoms or experience flu-like symptoms and never seek medical attention. Of those patients seeking medical care, the most common symptoms are fatigue, cough, chest pain, fever, rash, headache and joint aches. Some people develop painful red bumps on their shins or elsewhere that gradually turn brown (the medical term for these is "erythema nodosum"). These symptoms are not unique to Valley Fever and can be caused by other illnesses. Therefore, identifying Valley Fever as the cause of illness requires specific laboratory tests.
The usual course of disease in otherwise healthy people is complete recovery within six months. In most cases, the body's immune response is effective and no specific course of treatment is necessary. About five percent of cases of Valley Fever pneumonia (infection of the lungs) result in the development of nodules in the lung. These are small residual patches of infection that generally appear as solitary lesions, typically one to one and a half inches in diameter, and often produce no symptoms. On a chest x-ray, these nodules resemble lung cancer. Unfortunately, it is usually not possible to make a definite diagnosis without removing a part or all of the nodule by bronchoscopy, needle-aspiration or surgery. Another five percent of patients develop lung cavities after their initial infection with Valley Fever. These cavities occur most often in older adults, usually without symptoms, and about 50% of them disappear within two years. Occasionally, these cavities rupture, causing chest pain and difficulty breathing, and require surgical repair.
Of those patients with Valley Fever that seek medical attention, one to two percent develop disease that has spread (disseminated) to other parts of the body. The most common site of dissemination is the skin. Biopsies of skin lesions may reveal Coccidioides immitis when grown in culture. Bones and joints (especially the knees, vertebrae, and wrists) are other frequent sites of dissemination. The changes in bones and joints due to Valley Fever infection can be seen on x-rays and in CT-scans of the affected body part. Meningitis is the most serious and lethal complication of disseminated disease. Symptoms include headache, vomiting, stiff neck, and other central nervous system disturbances. A spinal tap is required for a definite diagnosis of meningitis.
A diagnosis of coccidioidomycosis is suspected only if a patient is known to have had exposure to the disease through travel or residence in an endemic area. Diagnosis can be confirmed by (1) microscopic identification of the fungal spherules in an infected tissue, sputum or body fluid sample, (2) growing a culture of Coccidioides immitis from a tissue specimen, sputum or body fluid and (3) detection of antibodies (serological tests specifically for Valley Fever) against the fungus in blood serum or other body fluids. Valley Fever skin tests* (called coccidioidin or spherulin) indicate prior exposure to the fungus, but, because reactivity is lifelong, skin tests are not particularly helpful in diagnosing a current infection. Commonly, a routine chest x-ray will detect Valley Fever cavities in a person with no symptoms and who may be unaware of ever having had Valley Fever. While positive blood test (serological) results almost always mean that a patient has Valley Fever, a third or more of patients with Valley Fever may actually have negative results. Therefore, it may be necessary to repeat the serologies periodically. *The skin test is currently not available
While there are no racial or gender differences in susceptibility to primary infection with coccidioidomycosis, differences in risk of disseminated infection do appear to exist. Men have a higher rate of dissemination than do women and several studies have shown that the rate of dissemination in African Americans and Filipinos is several times higher than in the rest of the U.S. population. Native Americans, Hispanics and Asians may also have a higher rate of dissemination than the general population, but these population differences are not well defined. Others at increased risk of disseminated disease are those persons with immune system deficiencies. In areas of the southwestern U.S. where Valley Fever is endemic, it is one of the most frequent opportunistic infections among HIV-infected patients. Patients who are immunocompromised due to organ transplants, Hodgkin's disease, diabetes, pregnancy (3rd trimester), or chronic corticosteroid therapy also have an increased risk of developing disseminated disease.
Most patients with Valley Fever recover with no treatment and will have life-long immunity. In severe cases, especially in those patients with rapid and extensive primary illness, those who are at risk for dissemination of disease, and those who have disseminated disease, antifungal drug therapy is used. The type of medication used and the duration of drug therapy is determined by the severity of disease and response to the therapy. The medications used include ketoconazole, itraconazole and fluconazole in chronic, mild-to-moderate disease, and amphotericin B, given intravenously or inserted into the spinal fluid, for rapidly progressive disease. Although these treatments are often helpful, evidence of disease may persist and years of treatment may be required. Surgical removal of cavities in the lung from Valley Fever is sometimes necessary. Surgical drainage of Valley Fever abscesses in bones or joints is also commonly performed.
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