Valley fever in dogs and cats

Valley fever is a fungal infection that dogs, and less often cats, catch by breathing in spores from the soil. Most dogs who get sick from it recover with treatment. It is not contagious to your other pets or to you.

Why it is so common here

Arizona has more canine Valley fever than any other state. A 2025 study of nearly 900,000 dog blood tests put Maricopa County at about 94 cases per 10,000 households a year.

The spores live in the soil and become a risk when it is disturbed and the dust is in the air, at any time of year. Dogs are more exposed than cats because they dig and sniff the ground. The only prevention is keeping your dog away from dusty, disturbed soil when you can.

Signs to watch for

Most dogs get the milder form, which stays in the lungs. It shows up as a harsh, dry cough, fever, a smaller appetite and low energy, usually about three weeks after the spores were breathed in.

In some dogs the infection spreads beyond the lungs. That can cause limping or swollen joints, a fever that does not go away, weight loss, eye inflammation, and less often seizures or heart problems.

Cats get Valley fever less often than dogs, but when they do, it spreads beyond the lungs more often, most commonly to the skin.

Testing

Valley fever is diagnosed with a blood test for antibodies, called a titer. We send it to a reference laboratory, and the result comes back in about six or seven days. Antibodies can take a few weeks to show up after infection, so an early negative result does not always rule it out. A high result does not mean the case will be more severe.

Treatment

Treatment is an antifungal medication given by mouth, most often fluconazole. A typical course lasts 9 to 12 months. Titers are rechecked every few months to track progress.

These medications can affect the liver, so bloodwork is checked during treatment.

Recovery

In general, more than 90% of dogs recover with treatment. Cases that reach the brain or several bones are harder to treat and can need lifelong medication.

Sources

• dvm360, understanding and managing Valley fever, June 2025
• University of Arizona Valley Fever Center for Excellence
• Journal of Infectious Diseases, 2025

About this page. Written for Sonoran Desert conditions and reviewed by a veterinarian at this practice. Last reviewed September 10, 2026.