Understanding Valley Fever in Dogs and Cats
- Oct 10
- 4 min read
By: Dr. Geoff McGee, Veterinarian
October 10, 2025
As residents of the Greater Phoenix Area, we share our beautiful desert environment with a unique challenge: Valley Fever (Coccidioidomycosis). Caused by the fungus Coccidioides (often called "Cocci"), this condition can cause serious illness in our beloved dogs and cats. Valley Fever can also infect humans.
Because we provide mobile, in-home care, we are often the first to notice the subtle, chronic changes associated with this disease. Here is a comprehensive guide to understanding Valley Fever – what to look for, how we diagnose it, and what treatment looks like for your pet.
What is Valley Fever and How Do Pets Get It?
Valley Fever is a fungal infection caused by spores found in the dry, dusty soil of the Southwestern United States (especially Arizona and parts of California). The disease is not contagious; it is acquired when a pet inhales the microscopic fungal spores that become airborne after digging, during dust storms, or through general outdoor activity.
Most pets (and people) who inhale the spores never get sick, as their immune system handles the infection without symptoms. However, in other pets, the fungus can proliferate and cause illness in two main forms:
Primary Disease (Lung-Limited): The infection stays within the lungs.
Disseminated Disease (Widespread): The infection spreads from the lungs to other parts of the body, such as the bones, joints, eyes, skin, and central nervous system.
Key Signs and Symptoms to Watch For
The clinical signs of Valley Fever can be vague, which is why chronic, unresolving symptoms warrant diagnostic testing. Since the disease affects dogs more frequently and differently than cats, it’s helpful to know the signs for both:
Primary Signs (Dogs & Cats)
Persistent Dry Cough (most common in dogs)
Fever that doesn't respond to antibiotics
Lethargy or decreased energy level
Decreased Appetite and unexplained Weight Loss
Signs of Disseminated Disease in Dogs
If the fungus spreads beyond the lungs, you may see more severe, localized symptoms, often related to the bones and joints:
Lameness or Limping
Swollen and Painful Joints or visible swelling on a limb
Swollen Lymph Nodes (especially near the shoulder blades or behind the knees)
Neurological Issues (seizures, head tilting, or back/neck pain)
Common Symptoms in Cats
Valley Fever is less common in cats, but when it occurs, it often presents differently:
Non-Healing Skin Lesions: The most common sign in cats are sores, abscesses, or draining tracts on the skin that refuse to heal.
Severe Lethargy and Hiding
Difficulty Breathing (Dyspnea)
Recommended Testing and Diagnosis
Diagnosis involves combining a physical exam with lab and imaging work. Since McGee Veterinary Service provides comprehensive in-home care, we can perform the initial testing right in the comfort of your home.
Valley Fever Blood Test (Titer)
What it measures: the level of antibodies your pet's body is making against the Coccidioides fungus.
What the results mean: A positive result means your pet has been exposed. The titer (level) helps us determine if your pet has an active infection.
Important Note: Early infections can sometimes show a false-negative result, requiring a re-test in a few weeks if symptoms persist.
Other Diagnostics
In complex or severe cases, your veterinarian may recommend advanced tests like a specialized antigen test (which looks for parts of the fungus itself), a biopsy of a skin lesion, or a referral for specialized imaging.
What Does Valley Fever Treatment Look Like?
Treatment is a long-term commitment, but the prognosis for pets with lung-limited disease is generally good when treated early.
1. Antifungal Medications
The standard treatment is an extended course of oral antifungal medication, most commonly Fluconazole.
Duration: Treatment typically lasts for a minimum of 6–12 months, and often longer. In cases where the infection has spread to the central nervous system, treatment may be required for life.
Monitoring: Since these medications can be taxing on the liver, we will schedule regular in-home rechecks with blood tests to monitor your pet’s liver function and ensure they are tolerating the medication well.
2. Supportive Care
Depending on the severity, your pet may also require:
Pain & Anti-Inflammatory Medication: To help manage joint pain and fever, improving their quality of life during treatment.
Nutritional Support: If the pet is lethargic or losing their appetite, we provide guidance and medication to help maintain their nutrition.
3. Follow-Up
We will repeat the Valley Fever titer test periodically (usually every 3-4 months) until the levels stabilize and the clinical symptoms have completely resolved. It is essential to complete the full course of medication and treatment prescribed by your veterinarian to prevent recurrence.
Concerned Your Pet May Have Valley Fever?
If your dog or cat is showing any of the common symptoms – a cough that won't go away, unexplained limping, or persistent lethargy – please don't wait. Early diagnosis and treatment are critical for the best outcome.
Contact McGee Veterinary Service at 623-396-9185 today to schedule an in-home evaluation. We are here to bring experienced, compassionate care and clear answers right to your door. To see if we cover your neighborhood, view our detailed Service Area Map.
McGee Veterinary Service offers in-home veterinary care and peaceful at-home euthanasia to Phoenix, Scottsdale, Paradise Valley, Cave Creek, Carefree, New River, Anthem, Peoria, Glendale, Litchfield Park, Surprise, Sun City, and Sun City West.
ABOUT THE AUTHOR
Dr. Geoff McGee is the owner of McGee Veterinary Service. He graduated from WSU College of Veterinary Medicine in 2017, completed a surgical internship, and founded a mobile practice in 2024 driven by his desire to better care for his senior dog. When not serving the community's pets, Dr. McGee enjoys hiking, camping, and spending quality time with his family.
