Valley Fever (Coccidioidomycosis) in Dogs
What is Valley fever?
Valley fever, or coccidioidomycosis, is a fungal (Coccidioides immitis and Coccidioides posadasii) infection most identified in arid climates in the southwestern United States, Mexico, and Central and South America. Regions with the highest case numbers in the USA are Arizona, Nevada, New Mexico, drier parts of California, Texas, southwestern Washington, and Utah. Research has recently shown that cases may also be appearing in new parts of the western USA. Many species can be affected, but dogs are particularly susceptible to the disease. Animals and people are infected when they inhale fungal spores that become airborne during dry and dusty conditions. Heavy rainfall promotes growth of the fungus in the soil, and when this is followed by extended drought, Valley fever epidemics can occur. Dogs that dig in dirt are at increased risk for infection, so Valley fever tends to occur in young to middle-aged, medium to large dogs that like to dig.
The fungus does not spread between pets, or between animals and people. However, if your pet is affected, you may have been exposed to the fungus in your shared environment.
What are the clinical signs of Valley fever in dogs?
Clinical signs of Valley fever in dogs are primarily respiratory. However, in some dogs—just like in humans—the fungus can spread to multiple tissues, including the brain, eyes, bones, and joints. As a result, clinical signs vary depending on the organs involved and the severity of the infection. Certain purebred dogs may be at increased risk for severe disease, such as weimaraners, Hungarian vizslas, and Dalmatians.
Signs of respiratory disease include cough, rapid breathing, fever, lethargy, and loss of appetite. Dogs with widespread disease can have skin masses, lameness, generalized pain, and heart failure. Those with brain involvement may demonstrate seizures or behavioral changes.
Some affected dogs can fight off the infection without exhibiting any clinical signs.
How is Valley fever diagnosed in dogs?
Valley fever in dogs is diagnosed through bloodwork and/or identification of the fungus in tissues (such as through biopsy).
How is Valley fever treated in dogs?
Valley fever in dogs is treated with long term (6-12 months) daily antifungal medication, usually fluconazole or sometimes itraconazole. The prognosis is good for dogs that undergo appropriate treatment for the respiratory form of the disease. Dogs with severe disease may need to be treated with an injectable antifungal drug known as amphotericin.
What is the prognosis for Valley fever in dogs?
The prognosis for dogs affected by Valley fever ranges from good to guarded depending on which tissues are involved and the severity of the infection.
How can Valley fever be prevented in dogs?
If you live in or visit affected areas (especially southern Arizona and south-central California), keep pets indoors as much as possible when conditions are windy or dusty, and discourage digging behavior. Add plants, gravel, and other landscaping to reduce dust in your yard. Keep pets away from areas that may have loose dirt, such as construction sites.
Valley fever vaccine clinical trials are in progress in dogs. Ultimately, a similar vaccine may be used to protect humans. If your dog has been in a region where the fungus is found and develops illness such as a cough, ask your veterinarian about Valley fever - early diagnosis can improve treatment outcomes.
For more information
Dogs Could Help Predict Valley Fever Spread in Humans
Valley Fever in Pets and Other Animals, CA Department of Public Health
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