Valley Fever

Also Known As: Coccidiodomycosis, Cocci

  • The causative organism is Coccidioides immitis, a fungus that lives in the soil of the desert in the Southwestern United States, Mexico, Central America, and parts of South America. The fungal organisms are inhaled and a lung infection is established which may spread to lymph nodes, eyes, skin, bones, or other organs. Although all animals and people in endemic areas are exposed to the fungus, only a few will actually develop infections and show symptoms.

  • Dogs of any age, breed, or gender can be affected by Valley Fever, but it is most common in young, medium to large breed, outdoor dogs. It is rare in cats.

  • The most common symptoms of Valley Fever include lethargy, weight loss, fever, decreased appetite, and coughing. Lameness may be seen if bone is infected and cloudy, painful eyes may be seen in ocular infections. Valley Fever can also infect the brain, causing seizures. Although uncommon, skin lesions of Valley Fever include nodules, abscesses, and draining lesions, especially over areas of bone infection.

  • See Clinical Signs.

  • Diagnosis of Valley Fever is by clinical signs, x-rays of the chest and/or affected bones, and specific blood testing for antibiotics against C. immitis, the causative fungus. Biopsis of skin lesions shows pyogranulomatous inflammation but fungal organisms may or may not be found.

  • The prognosis varies with the severity and chronicity of the disease. Animals with bone and neurologic involvement are more difficult to cure. Relapses are common, especially if treatment is not continued long enough, but with aggressive long-term therapy, most animals can be effectively treated.

  • The treatment for Valley Fever is long-term (9 months to over 1 year) oral antifungal medication which is continued for at least 2 months beyond the resolution of symptoms and ideally until negative blood testing for Valley Fever antibodies. Antifungal medication options include ketoconazole, itraconazole, and fluconazole.

  • Because the fungal organisms are ubiquitous in the Sonoran Desert life zones, prevention is not possible, however restriction of a dog's access to areas of disturbed earth such as construction zones may be helpful.