Signs of Valley Fever in Dogs — What Coronado & San Diego Pet Owners Should Know

Valley Fever — the common name for coccidioidomycosis — is a fungal infection caused by Coccidioides immitis, a pathogen that lives in the desert soil of the American Southwest, including parts of San Diego County. Dogs contract it by inhaling microscopic spores from disturbed soil during hikes, trips to the desert, or travel through endemic areas. It’s one of the most commonly misdiagnosed conditions in regional veterinary medicine — and San Diego dogs, including those in Coronado, are more at risk than many owners realize.

Where Does Valley Fever Come From, and How Do Dogs Get It?

Coccidioides spores live in dry, sandy, alkaline soil — the kind found throughout the desert regions east of San Diego, including Anza-Borrego Desert State Park, the Imperial Valley, and areas of Riverside and San Bernardino counties. When soil is disturbed by digging, wind, construction, or just walking through dry scrubland, spores become airborne and can be inhaled.

Dogs are far more susceptible than humans. They have their noses close to the ground, they dig, and they inhale significant volumes of air relative to their body size. A single afternoon hike through endemic terrain is sufficient exposure for infection.

Coronado itself is not high-risk desert terrain — but Coronado families frequently travel to hiking areas, campgrounds, and desert destinations where Valley Fever exposure is common. The dog who was fine on the drive home may begin showing symptoms 1–3 weeks later, long after the connection to the trip has faded from memory.

This delayed onset is one of the main reasons Valley Fever is so frequently missed. According to the Merck Veterinary Manual, coccidioidomycosis can mimic many other conditions, and dogs are often treated for other illnesses before the correct diagnosis is reached.

What Are the Symptoms of Valley Fever in Dogs?

Valley Fever presents differently depending on whether the infection remains localized in the lungs (primary form) or spreads to other parts of the body (disseminated form). Most dogs develop the primary form, which is less severe. A smaller percentage develop disseminated disease — and in these cases, the condition can become life-altering.

Primary (lung) Valley Fever — most common:

• Dry, harsh cough — often the first symptom owners notice
• Lethargy and low energy
• Reduced appetite or complete appetite loss
• Low-grade fever
• Weight loss over weeks to months
• Difficulty breathing in more advanced cases

Disseminated Valley Fever — occurs when the fungus spreads beyond the lungs:

• Painful, swollen joints — limping or reluctance to move
• Swollen lymph nodes, especially around the jaw or limbs
• Skin lesions, draining wounds, or lumps under the skin
• Seizures or neurological signs — if the fungus has spread to the brain or spinal cord
• Spinal pain — arching of the back, reluctance to climb stairs or jump
• Eye involvement — cloudiness, redness, or vision changes

The disseminated form can look like cancer, autoimmune disease, bone infection, or spinal disease — and has been misdiagnosed as all of these. If your dog has been to desert areas and is showing any combination of the above, Valley Fever belongs on the differential list.

How Is Valley Fever Diagnosed and Treated?

Diagnosis The primary test is a Valley Fever titer — a blood test that detects antibodies to Coccidioides. A positive titer confirms exposure and active infection; the titer level gives some indication of disease severity and helps guide treatment decisions. Chest X-rays are often taken alongside the titer to assess lung involvement. In cases of disseminated disease, additional imaging or spinal fluid analysis may be needed.

Importantly, a negative titer early in infection does not rule out Valley Fever — it can take several weeks after exposure for antibodies to reach detectable levels. A dog with strong clinical suspicion and a negative titer is often retested 4–6 weeks later.

If you’ve recently traveled with your dog to desert areas and your vet is working up a lethargy case, ask specifically about Valley Fever testing. Our diagnostic services at Nado Veterinary Care include regional disease panels appropriate for the San Diego area.

Treatment Valley Fever is treated with oral antifungal medications — most commonly fluconazole or itraconazole. Treatment is not short-term. Most dogs with primary pulmonary disease are treated for a minimum of 6–12 months. Dogs with disseminated disease often require treatment for 1–2 years or, in some cases, for life.

The good news: most dogs with primary Valley Fever respond well to antifungal therapy and go on to live normal, healthy lives. Dogs with disseminated disease can also do well with appropriate treatment, though the road is longer and outcomes depend on which organ systems are involved.

Titer levels are rechecked every few months during treatment to assess response and guide decisions about when — or whether — to discontinue medication.

Frequently Asked Questions

Can my dog get Valley Fever without leaving Coronado?

It’s possible but uncommon. True Valley Fever risk areas in San Diego County are primarily the drier, eastern inland regions — not the coastal areas where Coronado sits. However, the spores can theoretically be carried by wind, and construction in any sandy area disturbs soil. The much more common scenario is a dog who contracted it during a trip to the desert or an inland hiking area. Always mention recent travel to your vet when Valley Fever is a consideration.

Can I catch Valley Fever from my dog?

No. Valley Fever is not contagious between animals or from animals to people. Both dogs and humans contract it independently from the same environmental source — the soil. You cannot get Valley Fever from your dog’s cough, saliva, or contact.

How do I know if my dog’s lethargy is Valley Fever versus something else?

You can’t determine this at home — and neither can a vet without testing. The cough is a useful distinguishing clue: a dog with lethargy and a persistent dry cough who has been to desert terrain should have Valley Fever on the differential list. But the titer blood test is the only way to confirm it. This is one reason the history you give your vet — including travel — matters so much.

For a full overview of lethargy causes in dogs and the diagnostic process, see: Why Is My Dog Suddenly Lethargic and Not Eating? A Coronado Vet Answers

Is Valley Fever fatal in dogs?

Primary pulmonary Valley Fever has a good prognosis with treatment. Disseminated disease — particularly when it involves the brain or spinal cord — carries a more guarded prognosis, but many dogs still do well with aggressive, sustained antifungal therapy. The most important factor in outcome is early diagnosis and consistent treatment compliance.