Understanding Valley Fever in Dogs: Symptoms, Causes, and Care
Valley fever, medically known as coccidioidomycosis, is a significant health concern for dogs living in or traveling to certain arid regions. This disease is caused by the Coccidioides fungus, which thrives in dry, desert soils—especially across the southwestern United States (think Arizona, California, New Mexico, Texas, Nevada, Utah), northwestern Mexico, and even parts of Central and South America. It's also been spotted in California's Central Valley and Central Coast and south-central Washington state.
How Do Dogs Get Valley Fever?
The fungus grows as long filaments underground. When soil is disturbed—by digging, construction work, or just strong winds—it releases infectious spores called arthroconidia. Dogs (and other animals or humans) usually contract valley fever by simply inhaling these airborne spores. Once inside the lungs, the spores transform into spherules that can multiply rapidly.
Most healthy dogs' immune systems can contain the infection. However, puppies, senior dogs, or those with weakened immune systems are at higher risk for developing serious illness.
Which Animals Are Affected?
While valley fever is most common in dogs—largely because they sniff and dig in dirt—other animals like cats, llamas, alpacas, horses, cattle, goats, sheep, and wildlife can also be infected. But dogs remain particularly susceptible due to their behavior outdoors.
The Disease Process: What Happens After Exposure?
After a dog inhales the spores:
- The spores enter the lungs and become spherules.
- Spherules enlarge and release hundreds of endospores.
- If not contained by the immune system, these endospores can spread within the lungs—or travel to other organs.
Around 60-70% of exposed dogs show no symptoms at all; they may even become immune. The remaining cases develop illness—especially puppies, older dogs, or those with other health issues.
Main Forms of Valley Fever in Dogs
- Primary (Pulmonary) Disease: The infection stays limited to the lungs. Symptoms include a persistent dry cough, fever, lethargy (your dog just isn't themselves), loss of appetite, and weight loss. These signs often appear one to three weeks after exposure but can take longer.
- Disseminated Disease: Sometimes the infection spreads beyond the lungs. It might affect bones or joints (causing lameness or pain), eyes (inflammation or even blindness), skin (non-healing wounds), lymph nodes (swelling), or rarely the nervous system (seizures or neurological changes).
You might also see back or neck pain, swelling under the skin, swollen testicles, heart issues—or skin lesions/abscesses (especially in cats). Disseminated disease is more severe and requires aggressive treatment.
Is Valley Fever Contagious?
No—valley fever isn't contagious between animals or from pets to people. Infection only happens through inhaling environmental spores; you can't catch it directly from your dog.
Diagnosing Valley Fever
Your veterinarian will use several tools to diagnose valley fever:
- Serological blood tests: Measure antibody titers against Coccidioides.
- Chest X-rays: Look for lung changes typical of fungal infection.
- Cytology: Microscopic examination of samples from affected tissues.
- Fungal cultures: Sometimes used for confirmation.
- Other lab tests/imaging: As needed based on symptoms.
The signs can mimic pneumonia and other illnesses—so accurate diagnosis matters for effective treatment.
Treatment Options for Infected Dogs
Treating valley fever requires patience—a long course of antifungal medications is standard:
- Fluconazole
- Itraconazole
- Ketoconazole
Treatment may last six to twelve months—or longer if the disease has spread widely. In some cases (especially if there's brain involvement), therapy could be lifelong. Your vet will monitor liver function and bloodwork regularly because these drugs can have side effects. Supportive care might include anti-inflammatories for pain relief; IV fluids; or surgery if there are severe eye/skin problems.
Prognosis: What Can You Expect?
The good news? Most dogs with primary lung-only valley fever recover well with proper treatment—the survival rate tops 90%. If your dog has widespread or neurological disease though, recovery becomes more uncertain. Relapses do happen; ongoing monitoring is vital even after apparent recovery.
Prevention Tips: Keeping Your Dog Safe
- Avoid letting your dog play in dust or disturbed soil—especially where valley fever is common.
- Keep pets indoors during dust storms or construction activity nearby.
- Deter digging/sniffing in rodent holes or loose dirt when possible.
- Add grass/gravel/mulch to yards to cut down on dust exposure.
- A vaccine for canine valley fever may become available soon (it's under development).
If you live in—or travel through—an area where valley fever occurs and your dog develops respiratory symptoms like coughing/lameness/unexplained illness: tell your vet about your dog's recent locations right away. Early detection makes a huge difference for successful treatment!
