What is valley fever?

Valley fever is caused by a fungal organism called coccidioidomycosis. Because of that name, most people just call it valley fever.  This fungal infection typically originates in the lungs and may spread to the lymph glands, bones and other organs.

Coccidioidomycosis is acquired from the environment. The fungus is found most commonly in sandy, alkaline soil. Distribution in the United States is considered to be limited to the southwest desert region. Infection occurs via inhalation of the organism from the environment into the lungs. Infection then spreads from the lungs to other tissues. Any tissue may be infected. Infected dogs may cough and showed nonspecific signs such as decreased appetite, lethargy and weight loss. Lameness occurs in animals with bone or joint involvement, and seizures or behavioral changes may occur in animals with brain infection.

X-rays of the lungs may reveal abnormalities compatible with fungal infection. Routine blood and urine tests help determine how the infection is affecting various organ systems. Blood tests for serum antibodies to coccidioidomycoses are always useful.

The antifungal drugs itraconazole and fluconazole are generally effective. Those drugs must be given for prolonged periods and the response to treatment should be regularly evaluated by your veterinarian. Blood tests are commonly done before and every three months after beginning treatment. Animals are often re-evaluated every three to six months after treatment to look for further involvement of the fungus in the body and to see if treatment is successful.

Prognosis is variable, depending upon the extent of disease, severity of clinical signs and response to treatment. Strict adherence to treatment protocols is needed for the best response. Treatment of systemic fungal infections requires a commitment to months of medication and follow-up evaluations with your veterinarian. Relapses occur, and follow-up visits are important to recognize signs of possible relapse.


Dr. Karsten Fostvedt is a veterinarian at St. Francis Pet Clinic in Ketchum.

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