Introduction
Coccidioidomycosis, or “Valley Fever,” is an uncommon but extremely severe fungal disease in dogs that develops after inhalation (or less commonly, ingestion) of infectious arthroconidia released by spores of the fungus, Coccidioides immitis. This fungus thrives in hot, dry areas of the southwestern United States, Mexico and parts of Central and South America. Some dogs are infected without clinical signs and develop immunity to the organism. Unfortunately, others are infected and progress to life-threatening illness.
Symptoms of “Valley Fever”
Some dogs are exposed to the infectious stage of the organism but never become clinically ill. These animals probably never will be diagnosed or require treatment.
Young, male, medium to giant-breed dogs that live outside seem to be more commonly clinically affected by this disease. Boxers, Dobermans, Australian shepherds, Beagles, Scottish terriers and Cocker spaniels have been reported to be predisposed as well, as do dogs living in endemic areas that tend to “nose around in the dirt.” In those dogs that do develop clinical disease, the early signs tend to be nonspecific and primarily respiratory. They include a mild, chronic cough, which can be moist and productive or dry, hacking and harsh. Other initial signs are anorexia, weight loss, weakness, and lethargy.
As the infection becomes disseminated throughout the dog’s body, which usually takes more than 4 months after the onset of respiratory signs, the dog deteriorates to exhibiting diarrhea, vomiting, lameness, joint swelling, bone enlargement, neck or back pain, neurological deficits including seizures, vision abnormalities, skin ulceration with weeping sores, emaciation and fever unresponsive to antibiotic therapy. It is not known why Coccidioides immitis tends to especially attack the eyes and the bones of dogs, causing lesions in these areas. Again, once the dog is infected systemically, the condition becomes grave.