Valley Fever, medically called coccidioidomycosis, is a fungal infection caused by Coccidioides organisms in soil. Dogs can inhale fungal spores when they dig, run, or breathe in disturbed desert dust.
Valley Fever should be considered when your dog has an unexplained cough, fever, weight loss, or lameness, especially if your dog lives in or has traveled through the Southwest. Early testing can help identify disease before it spreads beyond the lungs.
The infection is common in parts of:
- Arizona
- California’s Central Valley
- New Mexico
- West Texas
- Utah
- Nevada
Many pet parents outside these regions have never heard of Valley Fever. Even in endemic areas, the disease is often missed because it can look like allergies, kennel cough, arthritis, bacterial infection, or cancer.
Why is Valley Fever so easy to miss?
Valley Fever begins after a dog inhales microscopic fungal spores from dry soil. Dogs are much more susceptible to developing illness than people because they spend more time close to the ground, where dust is disturbed by running, digging, and sniffing.
The initial infection usually affects the lungs. In some dogs, however, the fungus spreads through the bloodstream to other parts of the body. This is called disseminated Valley Fever.
The symptoms may develop gradually. Your dog may simply seem tired, lose interest in food, or start moving more slowly. These changes can be easy to attribute to aging or a minor illness.
Valley Fever is not usually spread from one dog to another. It is generally acquired from the environment.
What are the symptoms of primary respiratory Valley Fever?
The first form is called primary pulmonary Valley Fever, meaning the infection is mainly in the lungs. Some dogs have mild disease, while others develop pneumonia or significant respiratory illness.
Common signs include:
- A dry, hacking, or honking cough
- Fever
- Lethargy or reduced energy
- Decreased appetite
- Weight loss
- Rapid or labored breathing
- Exercise intolerance
- Enlarged lymph nodes
A cough may occur because of inflammation in the lungs. It can also result from swollen lymph nodes pressing near the windpipe.
These symptoms can resemble:
- Kennel cough
- Seasonal allergies
- A bacterial respiratory infection
- Heart disease
- Asthma-like airway irritation
- Lung cancer
- Other fungal infections
Some dogs improve from a mild lung infection without developing widespread disease. Others continue to worsen or later develop signs outside the respiratory system. That is why a persistent or unexplained cough deserves a veterinary evaluation.
What does disseminated Valley Fever look like?
Disseminated Valley Fever develops when the fungus spreads beyond the lungs. It may affect bones, joints, skin, eyes, the nervous system, lymph nodes, or the heart.
This form is more dangerous and often requires a longer, more intensive treatment plan.
Signs can include:
- Lameness, especially lameness that shifts between legs
- Swollen joints or limbs
- Bone pain
- Back or neck pain
- Weakness or difficulty standing
- Seizures
- Changes in behavior or coordination
- Draining skin lesions or soft swellings
- Non-healing wounds
- Enlarged lymph nodes
- Eye pain, redness, cloudiness, or vision changes
- Unexpected heart problems
- Swollen testicles in male dogs
The disseminated form may appear weeks to months after the initial respiratory infection. A dog may stop coughing and seem better before developing lameness or another systemic sign.
In some cases, dogs show no obvious respiratory symptoms at all. They may first present with a limp, bone pain, seizures, or a skin lesion. This is one reason Valley Fever is sometimes confused with arthritis, orthopedic disease, immune-mediated disease, or cancer.
How is Valley Fever diagnosed?
A veterinarian usually combines your dog’s travel history, symptoms, physical examination, bloodwork, imaging, and fungal testing. No single test should be interpreted in isolation.
A typical veterinary diagnostics workup may include:
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Antibody titers: Blood tests that look for antibodies produced in response to Coccidioides. A positive result supports exposure, but it does not always prove active disease because some exposed dogs remain healthy.
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CBC: A complete blood count that evaluates red blood cells, white blood cells, and platelets. It may show inflammation or anemia.
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Serum chemistry: A blood panel that assesses organ function, proteins, electrolytes, and other markers. It helps evaluate your dog’s overall health and monitor medication safety.
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Chest X-rays: Radiographs may show pneumonia, abnormal lung patterns, or enlarged lymph nodes.
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Bone or limb X-rays: These may help identify lesions associated with fungal infection of the bone.
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Cytology or biopsy: A sample from a skin lesion, lymph node, bone, or other affected area may sometimes reveal the organism directly.
Your veterinarian may also recommend additional imaging or specialized testing if your dog has neurologic, eye, or heart-related symptoms.
Why does the timing of a Valley Fever test matter?
Antibody tests are useful, but the result depends partly on when testing occurs.
A dog tested very early in the infection may not yet have produced enough antibodies for detection. This means a negative result does not always rule out Valley Fever when symptoms and exposure history are concerning.
Your veterinarian may recommend:
- Testing again after an interval
- Comparing a later titer with the original result
- Using X-rays and routine bloodwork alongside antibody testing
- Investigating another diagnosis if the clinical picture does not fit
A titer is a measurement of the level of antibodies in the blood. Higher or rising titers may support active or progressive infection, but titers must be interpreted with your dog’s symptoms and other test results.
Follow-up titers may be used during treatment. A falling titer can support improvement, but your dog’s energy, appetite, breathing, comfort, and mobility are also important measures of response. A titer by itself cannot determine whether treatment should stop.
How is Valley Fever treated in dogs?
Treatment usually involves prescription antifungal medication for several months. Common medications include fluconazole or itraconazole, although your veterinarian will choose a treatment based on the disease location, severity, your dog’s health, and potential medication risks.
Treatment may also include:
- Periodic CBC and chemistry monitoring
- Pain control for bone or joint involvement
- Seizure medication for nervous system disease
- Eye treatment for ocular inflammation
- Supportive care for poor appetite or weight loss
- Additional care for heart or other organ involvement
Dogs with lung-limited disease may respond more quickly than dogs with disseminated disease. Bone, neurologic, or heart involvement can require many months of medication and close follow-up. Some dogs relapse if treatment is stopped too soon.
The dog blood test cost is only one part of the financial picture. Treating early disease may involve testing, medication, and follow-up visits. Treating disseminated disease can require more extensive imaging, longer medication courses, specialist care, and repeated monitoring.
That is why early detection matters. Testing does not guarantee a simple or inexpensive treatment plan, but identifying Valley Fever before serious spread may be safer and substantially less costly than managing advanced disease.
If you are looking for a convenient starting point, Affordable Pet Labs’ Valley Fever testing page provides information about the company’s regional diagnostic services. You can also review how the testing process works or learn about in-home sample collection. Results should always be shared with your veterinarian for interpretation and treatment decisions.
Should your dog be tested for Valley Fever?
Talk with your veterinarian about Valley Fever testing if your dog meets one or more of these conditions:
- Your dog lives in Arizona, California’s Central Valley, New Mexico, West Texas, Utah, or Nevada.
- Your dog recently traveled through an endemic region.
- Your dog has an unexplained cough lasting more than a few days.
- Your dog has fever, fatigue, poor appetite, or unexplained weight loss.
- Your dog is limping without a clear injury.
- Your dog has swollen joints, bone pain, or back or neck pain.
- Your dog develops seizures, weakness, or unusual behavior.
- Your dog has draining skin lesions or enlarged lymph nodes.
- Your dog has eye inflammation, redness, cloudiness, or vision changes.
- Initial treatment for allergies, kennel cough, or arthritis has not helped.
Valley Fever can be frightening, but recognizing the possibility is a proactive step, not a reason to panic. A timely conversation with your veterinarian and the right dog health test can help distinguish this infection from other conditions that look similar.
This article is for educational purposes only. It is not a substitute for veterinary diagnosis, physical examination, or individualized treatment. If your dog has difficulty breathing, seizures, severe weakness, or sudden collapse, seek urgent veterinary care.
