Definition
“Valley Fever” is a common term for Coccidioidomycosis, which is an uncommon but extremely severe and potentially fatal disease in dogs caused by the fungus Coccidioides immitis.
How “Valley Fever” Affects Dogs
This fungus thrives in hot, arid areas of the deep southwestern United States, Mexico and parts of Central and South America. Not all dogs exposed to the fungi succumb to clinical disease, but unfortunately many do. Young, male, large-breed dogs that spend lots of time outdoors in endemic areas are at increased risk. Early signs of illness tend to be nonspecific and primarily respiratory. Others include anorexia, weight loss, weakness and lethargy. As the infection spreads, which can take months, affected dogs often develop diarrhea, vomiting, lameness, swollen joints, neck or back pain, seizures, vision abnormalities, weeping skin sores, emaciation and a fever unresponsive to antibiotics. Once a dog is infected systemically, the prognosis is grave.
Where is Valley Fever Found?
In the United States, Valley fever is diagnosed in dogs most often in states which include: Arizona, desert areas of California, Nevada, New Mexico, southwestern Texas and Utah. People who take their dogs with them on vacations to these areas have also reported that their dogs contracted the fungus. The fungus itself lies dormant in the soil during drought periods. When it rains, the fungus comes back to life as a mold which releases airborne spores.
Causes of “Valley Fever” in Dogs
“Valley Fever” develops after a dog inhales or ingests infectious microorganisms released by spores of Coccidioides immitis. The fungus persists naturally several inches deep in the soil of endemic areas and is dormant during periods of drought. After rainfall, earthquakes or other causes of soil disturbance, the fungi surface, sporulate and become airborne. Inhalation of fewer than 10 of these organisms can cause clinical disease. Older and immunocompromised animals seem to be at higher risk, as do those with poor nutritional support. “Valley Fever” cannot be transmitted between people and dogs and is not contagious between dogs.
Preventing “Valley Fever” in Dogs
The disease cannot occur unless a dog has lived in or traveled through a region where the organism is endemic. Contaminated soil in these areas – especially during dust or wind storms after rain – should be avoided.
Special Notes
While successful treatment is possible if the fungal infection is promptly and properly diagnosed, successful treatment can take months to years to complete. Diagnosis of “Valley Fever” is complicated by the fact that most laboratories regard the fungus as too dangerous to culture because of the significant risk of human infection. There is no vaccine currently available for this disease. The prognosis for dogs with only respiratory signs is quite good. For dogs with systemic disease, the prognosis is guarded to grave.