Valley fever — the common name for coccidioidomycosis — is a fungal infection caused by the soil-dwelling organism Coccidioides immitis and Coccidioides posadasii. Dogs contract valley fever by inhaling microscopic fungal spores (arthroconidia) that become airborne when contaminated soil is disturbed by wind, digging, or construction. Valley fever is not contagious between dogs or from dogs to humans — infection requires direct inhalation of environmental spores.
Where Is Valley Fever Found and Which Dogs Are at Risk?
Coccidioides species thrive in hot, dry, alkaline soils in the American Southwest — particularly the low deserts of Arizona (especially Phoenix, Tucson, and the surrounding Sonoran Desert), southern California, New Mexico, Texas, Nevada, Utah, and northern Mexico. Any dog living in or traveling through endemic areas can be infected; studies estimate that in some endemic areas, up to 70% of resident dogs have been exposed without developing overt disease. Young dogs and immunocompromised animals appear to develop severe disseminated disease at higher rates.
Symptoms of Valley Fever in Dogs
The most common form is primary pulmonary infection, presenting with signs that can easily be mistaken for a routine respiratory illness. A dry, harsh cough is the hallmark symptom. Fever, lethargy, reduced appetite, and weight loss accompany the cough. In 20-40% of infected dogs, the fungus spreads beyond the lungs through the bloodstream (dissemination). The joints and bones are the most common sites — affected dogs develop painful lameness or bony swellings. Skin involvement produces draining abscesses. CNS dissemination causes seizures, head tilt, and behavioral changes.
Diagnosing Valley Fever in Dogs
Diagnosis begins with a compatible history and clinical signs. Chest X-rays typically show a diffuse pattern throughout the lungs. The most widely used diagnostic test is the Cocci serology titer — a blood test that measures antibodies against Coccidioides antigens. A positive titer in a dog with compatible clinical signs is strongly supportive. Titer levels loosely correlate with disease severity and are used to monitor treatment response.
Treatment and Management of Valley Fever in Dogs
All dogs with clinical valley fever require antifungal medication. The azole class of antifungals — fluconazole, itraconazole, and ketoconazole — are the mainstays of treatment. Fluconazole is particularly favored because it penetrates the CNS and is available in generic form, making long-term treatment more affordable. Treatment is required for a minimum of 6-12 months; dogs with disseminated bone or CNS disease often require 1-2 years or even lifelong suppressive treatment. Response is monitored by repeated serology titers every 3-6 months.
Can my dog give me valley fever?
No. Valley fever is not transmitted from dogs to humans or between dogs. Both humans and dogs contract it by inhaling spores from the soil. A dog with valley fever poses no infection risk to household members.
How long does it take for valley fever symptoms to appear in dogs?
Symptoms of primary pulmonary valley fever typically appear 1-3 weeks after exposure. Disseminated disease can take months to years after the initial lung infection to manifest, so dogs may not show joint or bone symptoms until long after initial exposure.
Is valley fever in dogs curable?
Many dogs with primary pulmonary valley fever are cured with 6-12 months of antifungal medication. Dogs with disseminated disease may achieve remission but sometimes require lifelong suppressive therapy to prevent relapse.
What does valley fever cough sound like in dogs?
The cough associated with pulmonary valley fever is typically dry, harsh, and persistent — similar to the cough associated with kennel cough. Dogs with valley fever cough may also show fever, weight loss, and lethargy alongside the cough.
How much does valley fever treatment cost for dogs?
Treatment costs vary depending on the antifungal prescribed, the dog’s size, and the duration of treatment required. Generic fluconazole is relatively affordable, but large-breed dogs requiring years of daily medication incur significant cumulative costs. Pet insurance that covers infectious disease can help offset these costs.