Coccidioidomycosis in Cats
My veterinarian said my cat has “Valley Fever.” What is this disease?
Valley Fever is another name for a disease called “coccidioidomycosis.” Coccidioidomycosis is a fungal disease caused by the soil fungus Coccidioides immitis. Coccidioides immitis is found primarily in the southwestern United States, and is most commonly located in Arizona, southern California, and southwestern Texas. It’s also occasionally found in Nevada, New Mexico, and Utah. The organism grows down several inches in the soil, and can survive the high temperatures of the desert regions. During the rainy season, Coccidioides immitis can return to the surface and sporulate, allowing infective spores to be spread by the wind.
The early signs of coccidioidomycosis include fever, lethargy, poor appetite, coughing, and joint pain. The cat may develop lameness and/or weakness, as well as back and neck pain. In severe cases, if the organism spreads throughout the body, the cat may develop seizures or blindness.
Most cats who develop coccidioidomycosis are young. Perhaps this is the demographic of cats who tend to be more active outdoors. Cats who dig in the dirt or who spend time outdoors following a dust storm may be a greater risk for exposure.
How did my cat get this fungal disease?
Coccidioidomycosis occurs after the cat inhales spores. In a susceptible cat, inhalation of fewer than 10 spores can cause illness.
How is coccidioidomycosis diagnosed?
Diagnosis of coccidioidomycosis in cats can be challenging because the symptoms are not specific for this disease. The first wave of symptoms typically includes fever, coughing, and difficulty breathing. Should the disease spread to other parts of the body, the symptoms depend on the tissues and organs involved. The cat may exhibit lameness, joint swelling, or swelling in bones. The lymph nodes may be enlarged. There may be nervous system dysfunction. The eyes may become inflamed causing vision problems. Finally, the skin may develop sores that will not heal, or draining tracts. X-rays of the chest may demonstrate lung lesions, and X-rays of affected bones may assist in diagnosis.
While coccidioidomycosis can be definitively diagnosed via biopsy, the most common way it is diagnosed is by testing for antibodies to the organism.
How is coccidioidomycosis treated? How long will my cat have to be treated?
Most cats with coccidioidomycosis are treated at home rather that in the hospital. This is a very serious illness requiring long-term treatment –for many cats this means treatment for at least one year. There are several oral medications from which your veterinarian may choose to treat this disease.
What sort of follow-up is required for cats who are treated for coccidioidomycosis?
Cats being treated for coccidioidomycosis will have repeated measurement of their antibodies to this organism. Levels are typically measured every 3 - 4 months, and need to be treated until the levels fall to less than 1:4. Regular monitoring of kidney and liver function may also be recommended. If needed, cough suppressants may be prescribed if severe coughing develops.
Unfortunately, coccidioidomycosis carries with it a guarded to grave prognosis, and while cats may improve during medical therapy, relapses are common. Overall recovery from coccidioidomycosis has been reported at between 60% and 90%.
Why don’t all the outdoor cats in Arizona have this disease?
Interestingly enough, despite the presence of Coccidioides immitis in the soil (and soil is everywhere), coccidioidomycosis is not very common, even in the endemic areas of the US. Asymptomatic infections may occur, in which cats are exposed, but develop immunity without experiencing the signs of full-blown disease.
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