Overview

Valley Fever or Coccidioidomycosis develops from inhaling an infective agent of a fungus. The fungus Coccidiodes immitis lives in the desert soil of the Lower Sonoran life zone, in the low desert regions of Arizona, New Mexico and southwestern Texas and the central deserts of California. Dogs comprise most of the cases with young males of larger breeds such as Doberman, German Shepherd Dog and Boxer more susceptible. Middle-aged cats may contract Valley Fever.

The life cycle of the fungus begins in the desert soil where it matures and dries into strands of cells. These fragile strands break into individual spores, arthroconidia or arathrospores, when the soil is disturbed. The animal needs to inhale only a few spores for infection. The inhaled spores enter a spherule (parasitic cycle) and grows until bursting. As hundreds of endospores release, each endospore develops a new spherule. Infection spreads in the lungs until destroyed by the immune system. Valley Fever develops when the immune system fails to kills the spherules and endospores that spread.

Valley Fever occurs in four forms: asymptomatic, acute respiratory form, disseminated and ulcerative skin lesions.

Symptoms and Diagnosis

About seventy percent of dogs that inhale the Valley Fever spores are asymptomatic and can control the infection. Other dogs may develop the disease that can range from very mild to severe, with some cases ending in death. Approximately three weeks after infection, early symptoms of primary pulmonary Valley Fever include coughing, fever, weight loss, depression, lack of energy, and appetite loss. A developing infection can show as pneumonia on radiographs. Dogs may sound like they are suffering from bronchitis when their swollen lymph nodes press on their windpipe leading to irritation and coughing.

Disseminated Valley Fever may show symptoms of lameness or swelling of limbs, bones and joints. Back or neck pain, soft swelling under the skin, swollen lymph nodes, skin ulcerations or draining tracts with fluid are other signs. Dogs suffering from Valley Fever may have an eye inflammation. Pet may also experience lethargy and lack of appetite. Cats may appear more ill during diagnosis. Non-healing skin ulcerations, weight loss and poor appetite are other symptoms.

Diagnosis involves running a Valley Fever test and a biopsy on skin lesions. Suspicion of the disease involves consideration of the dog’s travel history, symptoms and results of tests. Tests can include blood test and blood cell counts that can rule out other conditions. Chest x-rays can indicate large lymph nodes and lung infiltration. Blood tests that involve cocci test, cocci serology and cocci titer can check the blood for antibodies produced again the Valley Fever fungus.

Treatment

Treatment of Valley Fever can include antifungal medication given as daily pills or capsules. Common medications include Ketoconazole (Nizoral), Itraconazole (Sporanox) and Fluconazole (Diflucan). Valley Fever can relapse and takes a long time to clear. Monitoring liver enzymes is important. Owners can offer supportive care through cough suppressants, pain and fever relief, nutritional support and hospitalization. Dogs that receive early diagnosis and therapy can have a good prognosis. However, dogs suffering from the disseminated infection face a more guarded prognosis.

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