Valley Fever

Robin Paterson, D.V.M.
Cerbat Cliffs Animal Hospital

Coccidiodomycosis, more commonly known as Valley Fever, or San Joaquin Valley Fever (named after California’s San Joaquin Valley) is fungal disease which occurs only in the Lower Sonoran Desert including parts of Southern California, Arizona, New Mexico, Texas, Mexico and parts of Central and South America. The fungal spores of Coccidiodes immitis live in the dirt which is typically sandy and alkaline, and thrive in the dry, hot climate. The spores are then inhaled into the lungs and may cause respiratory disease, or if permitted to spread, can affect multiple organ systems including the lungs, skeletal system, skin, nervous system/eyes, spleen, heart and kidneys. Valley Fever most commonly affects dogs and humans, but there have been documented cases in cats, cattle, horses and other mammals, though these are relatively uncommon occurrences.

The spores are spread more rapidly in the environment through disruptions in the soil such as construction, digging, heavy rains or winds, dust storms, and earthquakes. It is important to remember that it is extremely unlikely for Valley Fever to be spread from one dog to another (or from dog to person and vice versa.) Many animals that are exposed never develop antibodies or show any signs of disease.

Signs and symptoms

The signs of Valley Fever are variable and may include some or all of the following: lethargy, weight loss, anorexia, weakness, coughing, joint pain/lameness, firm swellings on the limbs or occasionally, other bones, soft tissue swellings, fever, swollen lymph nodes and, much more rarely, draining skin lesions, blindness, and seizures.

There are different sources listing certain breeds as potentially having a higher incidence of contracting this disease, however, in our veterinary hospital, we do not appreciate a breed predilection, other than large breed dogs appear to be more likely to contract the disease with an age range of 4 months to geriatric and no appreciable difference in susceptibility between males versus females.

Diagnosis

Though there are multiple tests that can be performed to detect Valley Fever, the most common, and least invasive test is a blood antibody test that can be sent to a laboratory and can confirm a positive result and titer. In addition, your veterinarian will also likely check a complete blood count, serum blood chemistry and urinalysis to assess for any other underlying illness. S/he may also perform chest or limb radiographs, particularly if your dog has a history of coughing/other respiratory disease, or limb pain/swelling. Other, less common tests associated with Valley Fever diagnosis include cytology or biopsy with culture and sensitivity and fungal stains of draining skin wounds or abscesses. It should be noted that culturing the organism (i.e. growing the organism in the lab) is potentially very dangerous as this sporulated form of the disease is highly infectious and can infect lab personnel.

Treatment

The treatment for Valley Fever is a long-term (usually 6-24 months) course of antifungal medication. There are several effective oral antifungal medications available. Your veterinarian will select one that your dog is most likely to tolerate well. All of the drugs in this class have side effects. The most common are anorexia, vomiting and diarrhea and elevated liver and kidney enzymes. Because some dogs may be more affected by these side effects, your veterinarian may change medications during your dog’s treatment course, or prescribe various supplements to alleviate some of these effects. During the course of treatment, your dog will need regular check-ups and repeated bloodwork and/or radiographs to assess the efficacy of treatment, and to determine whether any dosing changes need to be made. In the case of severe systemic disease, your dog may be hospitalized for stabilization and treatment, though it should be noted that cases requiring this level of care are infrequent.

Prognosis

The long-term prognosis for appropriately treated, non-disseminated Valley Fever cases is good, with 90% of dogs about responding favorably to the oral antifungal medications. There are some patients that require longer than average treatment in order to attain a negative blood test, and there are a few cases that become clinically normal but are never able to completely clear the infection (as determined by a positive blood antibody.) However, dogs that have severely disseminated disease, and/or who have neurologic or cardiac involvement have a much higher likelihood of treatment failure, and the prognosis is guarded in these cases.

As with any chronic medical condition, your veterinarian will work with you and your dog to create a treatment plan that is individually tailored to your pet, and will be able to answer any specific questions that you may have.

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