Valley Fever in Dogs: Coccidioidomycosis Signs and Care

If you live in or travel through the dry parts of the American Southwest, you may have heard your veterinarian mention valley fever. This fungal infection, known medically as coccidioidomycosis, starts when a dog breathes in microscopic spores from the soil. Many exposed dogs never become sick, but others develop a lingering cough, fever, low energy, or weight loss, and in some dogs the infection spreads to the bones, skin, or eyes. Because early signs resemble many other illnesses, valley fever is easy to miss. This guide explains where the fungus lives, how dogs pick it up, lung-only versus spread-out disease, how veterinarians test for it, what long-term antifungal care involves, and practical ways to limit dust exposure.

Important: This article shares general educational information for pet owners and is not a substitute for an in-person veterinary examination, diagnosis, or treatment. For any medical concern or emergency, contact your veterinarian promptly.

What Valley Fever Is and How Dogs Get It

Valley fever is caused by fungi in the genus Coccidioides, which live in the top layers of soil in hot, dry regions. In the soil they grow as fine threads that break apart into tiny, lightweight spores. When the ground is disturbed, those spores float into the air, where a dog, cat, or person can inhale them.

Inside the lungs, the fungus changes form. It grows into round structures called spherules, which fill with internal spores, burst, and release more into the surrounding tissue. A healthy immune response often contains this quietly. When it does not, the infection inflames the lungs and sometimes travels through the bloodstream to other parts of the body.

Because valley fever is fungal, not bacterial, ordinary antibiotics do not address it. That is one reason a thorough workup matters when a dog in an affected area has an unexplained cough or fever.

Where the fungus lives and how dogs are exposed

In the United States, Coccidioides is best known in southern Arizona and the Central Valley and southern regions of California. It also occurs in parts of New Mexico, west Texas, southern Nevada, and Utah, as well as Mexico and parts of Central and South America. Your veterinarian is the best source for how common it is where you live.

Dogs become infected by breathing in spores, not by eating them or through contact with a sick pet. Activities that raise dust and put a dog's nose near the ground increase exposure:

• Digging: dogs that dig in yards, open lots, or along trails put their noses right in loose soil.
• Sniffing undisturbed ground: nosing through brush and dirt on desert walks and hikes.
• Construction and landscaping: grading and trenching lift large amounts of soil into the air.
• Wind and dust storms: strong winds carry spores well beyond where the soil was disturbed.
• Seasonal patterns: cases often follow a rainy season that lets the fungus grow, then a dry, windy period that sends spores airborne.

Even mostly indoor dogs can be exposed, because dust travels. A dog that visited the Southwest months ago can show signs after returning home, so mention any trips to your veterinarian.

Primary Respiratory Disease: The Lung Form

Most dogs that become ill first show lung-related signs, called primary or pulmonary disease. Signs often appear a few weeks after exposure and may come on gradually.

• Cough: often dry and harsh, lasting longer than a typical mild cough. Our guide to coughing in dogs and cats covers other common causes.
• Fever: a dog may feel warm, seem achy, or tire quickly.
• Low energy: less interest in walks, play, or greeting you at the door.
• Poor appetite and weight loss: eating less over days to weeks, with gradual loss of body condition.
• Faster or harder breathing: in more advanced cases, especially when chest lymph nodes enlarge.

These signs overlap with kennel cough, pneumonia, heart disease, and more. A persistent cough or fever in a dog from an affected region warrants a veterinary exam rather than a wait-and-see approach.

Disseminated Disease: When Infection Spreads

In some dogs the fungus moves beyond the lungs, called disseminated disease. It can appear alongside the cough or later, sometimes without obvious breathing signs. It usually needs a longer medication course and closer follow-up.

Bones and lameness

Bone involvement is one of the most recognized forms of spread in dogs, often in the legs. A dog may limp, favor one leg, or have a firm, warm swelling over a bone. Lameness that shifts between legs or does not improve with rest deserves attention. See our guide to sudden limping for first steps.

Skin and draining tracts

Some dogs develop lumps or open sores that drain fluid, often over an infected bone. These may close and reopen, and can be mistaken for ordinary wounds.

Eyes and other areas

Inflammation inside the eye can cause redness, cloudiness, squinting, light sensitivity, or vision changes, and warrants prompt care. Less commonly, the infection reaches the heart, brain, spinal cord, or other organs, causing weakness, fluid buildup, collapse, or seizures.

How Veterinarians Test for Valley Fever

No single quick test answers every question, so veterinarians combine history, exam findings, lab work, and imaging. Expect questions about where your dog lives and travels and how long signs have been present.

• Antibody titer blood tests: the most commonly used test, measuring antibodies against the fungus. A positive result supports infection, and the level helps guide decisions. An early negative result does not always rule it out, so retesting may be recommended.
• Chest X-rays: can show lung changes and enlarged lymph nodes. Our guide to X-rays and ultrasound for pets explains what to expect.
• Bone X-rays: for limping dogs, to look for bone changes typical of fungal infection.
• Routine bloodwork: a blood count and chemistry panel assess overall health and organ function before long-term medication.
• Tissue samples: fluid or tissue from a lump, draining tract, or lymph node may show the fungus under a microscope.
• Eye exam: checking eye pressure and the inside of the eye, sometimes with a veterinary ophthalmologist.

Interpreting titers takes experience, especially where some healthy dogs have been exposed in the past. Your veterinarian weighs results together with signs and imaging.

Antifungal Medication and Long-Term Care

When valley fever is confirmed or strongly suspected, veterinarians usually recommend oral antifungal medication, most often from the azole antifungal class. The specific drug, dose, and schedule must come from your veterinarian, given exactly as prescribed by your veterinarian. Never substitute a human antifungal or change the amount on your own.

The fungus responds slowly, so therapy usually lasts many months, and disseminated cases may need a year or longer. Some dogs need medication for life. Ending the course early because a dog seems better is a common cause of relapse.

Your veterinarian may also prescribe medication for pain, cough, or inflammation, or suggest nutritional support for dogs that have lost weight. Tips in our guide on giving your pet medication can make daily pills easier. Ask before hiding pills in food, since some medications are best given with or without a meal.

Monitoring During and After Therapy

Follow-up visits show whether the infection is responding and whether medication is well tolerated.

Your veterinarian decides when ending medication is reasonable, based on how your dog looks, imaging, and titer trends. Relapse can occur months later, so keep watching for returning signs.

Is Valley Fever Contagious?

In the usual sense, no. Valley fever comes from breathing in spores from the environment, and the form of the fungus inside the body does not normally spread through coughing. An infected dog is not considered a typical source of infection for other pets or people at home. Family members and pets can both get sick, but because they share the same dusty surroundings, not because one passed it on.

Rarely, the fungus can grow on bandages from draining wounds, so wear gloves when handling them and follow your veterinarian's instructions. Anyone with a weakened immune system should talk with their own physician.

Cats can also get valley fever, though it is reported less often. Skin lumps and draining sores are commonly described in cats, and the same testing and antifungal approach applies under veterinary guidance.

Limiting Your Dog's Dust Exposure

There is currently no vaccine for valley fever in dogs, and spores cannot be avoided entirely in affected areas. Practical steps can still limit how much dust your dog breathes:

• Discourage digging: redirect diggers to toys, puzzle feeders, or a sandbox with clean sand.
• Cover bare ground: grass, gravel, or pavers keep loose soil from blowing around the yard.
• Skip dusty outings: keep your dog indoors during dust storms and avoid active construction sites.
• Stay on paths: leash walks on sidewalks and established trails limit nosing through desert ground.
• Dampen soil before yard work: lightly watering dirt before digging cuts down airborne dust.

Early detection is the other half of the plan. Knowing the signs and seeking an exam sooner gives your dog the best chance of a smoother course.

When to Call Your Veterinarian

Schedule an exam if your dog lives in or has visited an affected area and shows any of these signs:

• A cough lasting more than a week or two, or one that keeps returning
• Fever, low energy, poor appetite, or gradual weight loss
• Limping, swelling over a bone, or lameness that shifts between legs
• Lumps or sores that drain fluid or keep reopening
• Red, cloudy, or squinting eyes

Contact your veterinarian or an emergency clinic right away if your dog

• Is laboring to breathe or has pale or bluish gums
• Collapses, is very weak, or has a swollen belly
• Has a seizure or a painful eye with sudden vision loss
• Refuses all food or vomits repeatedly while on antifungal medication

Common Mistakes and Myths

Myth: Only dogs that live in the desert get it.

Fact: dogs that visited affected regions, even briefly, can become ill after returning home.

Mistake: Ending medication when the dog looks better.

Improvement often comes well before the infection is controlled. Continue until your veterinarian advises otherwise.

Myth: A negative test always rules it out.

Fact: antibodies can take time to rise, so retesting may be needed if signs continue.

Frequently Asked Questions

Can a dog recover from valley fever?

Many dogs do well with consistent antifungal medication and monitoring. The outlook depends on how widespread the infection is, so ask your veterinarian about your dog.

Should I test a healthy dog?

Routine screening is not usually needed, but some veterinarians in affected areas discuss baseline testing. Ask what makes sense locally.

Key Takeaways

Valley fever is a fungal infection dogs acquire by inhaling soil spores in dry regions of the Southwest. Ill dogs often show a lingering cough, fever, low energy, and weight loss, while disseminated disease can cause limping, draining sores, and eye problems. Veterinarians use antibody titers, X-rays, bloodwork, and sometimes tissue samples to confirm it. Azole antifungal medication, given as prescribed by your veterinarian, usually continues for many months with regular rechecks. It is not contagious between pets and people in the usual sense. Limiting dust exposure and seeking an exam early are the best steps you can take.