🌵 Valley Fever in Pets: A Vet’s 2025 Guide to Coccidioidomycosis in Dogs and Cats 🩺

By Dr Duncan Houston, BVSc

Valley Fever, medically known as Coccidioidomycosis, is a fungal infection most commonly contracted by dogs—and occasionally cats—through inhalation of dust in arid desert environments. 🌬️🐾 Though often mild, this disease can become life-threatening if it spreads beyond the lungs. In this 2025 veterinary guide, I’ll walk you through what causes Valley Fever, how to recognize it, how it's diagnosed, and the treatment options that give pets the best chance at recovery. 🐶🐱💊

🌎 Where Does Valley Fever Come From?

This fungal disease was originally identified in California’s San Joaquin Valley, hence the name "Valley Fever." Today, it's found in multiple desert areas, including:

• 🌵 The American Southwest: Arizona, New Mexico, Texas, Nevada, Utah, and California
• 🏜️ Central and South America’s arid zones
• 🌬️ Expanding areas in Washington and Oregon

The fungal culprit is Coccidioides spp.—soil-dwelling organisms that become airborne when dirt is disturbed by wind, farming, construction, or even natural events like earthquakes. Once inhaled, the spores can infect the lungs and potentially spread throughout the body. 🦠

🦠 About the Fungus

Coccidioides immitis and Coccidioides posadasii are the two fungal species responsible for Valley Fever. Their spores, called arthroconidia, are released after rainfall and carried by wind. 🌧️➡️💨 These spores can survive extreme environmental conditions and remain dormant in soil until disturbed.

Only a few spores are needed to cause infection in a susceptible animal. The risk is highest during dry seasons following rainfall, when spores are most likely to be released into the air. 🏜️

😷 Who Gets Sick? Not All Pets Do

It’s estimated that about 60% of exposed pets never show symptoms. They may only be discovered to have Valley Fever later through routine antibody testing.

The remaining 40% develop clinical disease. Illness typically begins 1–3 weeks after exposure and is most commonly marked by:

• 🐶 Persistent or worsening cough
• 🌡️ Fever
• ⚖️ Weight loss
• 🍽️ Appetite reduction

If the infection stays in the lungs, recovery is likely with proper treatment. But if the fungus spreads (known as disseminated Valley Fever), it can affect bones, skin, eyes, liver, or even the nervous system—making it far more dangerous. 🧠🦴👁️

🔍 Signs of Dissemination

When Valley Fever leaves the lungs and spreads to other parts of the body, you may see:

• 🦴 Limping or joint swelling (bone involvement)
• 👁️ Red, painful eyes or blindness (eye involvement)
• 😴 Lethargy and weakness
• 🧠 Seizures or neurological symptoms

The disease often follows a progression, starting in the lungs and then invading other organs—usually several months after the initial symptoms. This delay can make it tricky to diagnose early. ⏳

🤒 Is Valley Fever Contagious?

No. Valley Fever is not contagious between animals or from pets to people. Transmission occurs only through inhalation of spores from the environment—not from contact with an infected pet. 🌬️

🧪 Diagnosing Valley Fever

Diagnosis is usually made through a combination of clinical signs, imaging, and lab tests. Here's how vets confirm the disease:

1. Radiographs (X-rays) 🩻

Chest X-rays often reveal enlarged lymph nodes or lung infiltrates. While not specific to Valley Fever, they help rule out other causes like pneumonia, heart disease, or tracheal collapse. 🫁

2. Cytology or Tracheal Wash 🌫️

In cases where fluid from the lungs is collected and analyzed, fungal spherules can occasionally be seen under a microscope. This provides direct visual confirmation. 🔬

3. Blood Testing 🧬

• 🧪 Antibody testing looks for immune response to the fungus. This is the most common method but should be interpreted with care, as many animals test positive without symptoms.
• 🧫 Antigen testing detects fungal proteins and is useful when combined with antibody testing to improve accuracy.

Important: A positive test alone does not confirm active disease—it must be correlated with symptoms. 💡

💊 Treatment of Valley Fever

Treating fungal infections takes time—often up to a year or more. The goal is to resolve symptoms, improve radiographic images, and reduce antibody levels (though antibodies may never drop to zero).

Common Antifungal Medications:

• 💊 Fluconazole – well-tolerated and commonly used
• 💊 Itraconazole – more potent but harder on the liver
• 💊 Ketoconazole – effective but with more side effects

Liver enzyme monitoring is critical during treatment as these medications can stress the liver. Blood work is usually done every few months to ensure safety. 🧪🩸

📈 Prognosis: What to Expect

Good news: If the infection is limited to the lungs, the prognosis is excellent with a recovery rate near 90%. 🎉

However: Disseminated disease is more serious. Bone involvement can require amputation, and eye involvement often leads to enucleation (surgical eye removal). When the nervous system is affected, outcomes are much more guarded. 😟

Factors that improve prognosis include:

• 🚨 Early diagnosis
• 📋 Consistent medication administration
• 🔄 Regular monitoring and follow-up

🚫 What Not to Do

Pets fighting Valley Fever should avoid immunosuppressive medications like corticosteroids unless absolutely necessary, as these can worsen fungal dissemination. ❌💉

🛡️ Prevention Tips

While there's no vaccine against Valley Fever, here are tips to reduce your pet’s exposure:

• 🚫 Avoid outdoor play during dust storms
• 🌬️ Keep windows closed on windy days
• 🧹 Minimize digging or exposure to disturbed soil
• 🌵 Use air purifiers in dusty regions
• 📲 Use the Ask A Vet app to monitor symptoms or ask about coughing, appetite loss, or limping

🏥 When to See the Vet

If your pet shows any of the following signs, particularly if you live in or have traveled through a desert region, seek veterinary attention immediately:

• 🌬️ Persistent or unusual cough
• 😴 Unexplained fatigue
• 🏃‍♂️ Limping or joint pain
• 👁️ Red or cloudy eyes
• 🌡️ Fever that doesn’t respond to typical treatment

📲 Ask A Vet Support for Valley Fever

Valley Fever can be confusing to manage, but you don’t have to do it alone. Download the Ask A Vet app or visit AskAVet.com for immediate help. Our licensed vets can walk you through testing options, treatment plans, or even help interpret lab results. 🧑‍⚕️📱

🎯 Final Thoughts from Dr Duncan Houston

Valley Fever is a serious condition—but with early diagnosis and proper care, most pets can return to full health. 🌈 Whether your dog is a desert explorer or your cat has started coughing after a trip to the Southwest, awareness is your first and best line of defense. 🛡️

If you're worried about symptoms or need a second opinion, reach out through AskAVet.com. And remember: a few spores can cause serious illness, but a lot of love and the right treatment can go a long way in healing. 🐾💙