Valley Fever in Cats: An Overview
Dog Breeds
“Valley Fever” is a common term for Coccidioidomycosis, which is an uncommon but extremely severe and potentially fatal disease caused by the fungus, Coccidioides immitis. This disease is rare in cats and uncommon in dogs, although dogs are more frequently affected than cats. People also are susceptible to this fungal infection.
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Definition
“Valley Fever” is a common term for Coccidioidomycosis, which is an uncommon but extremely severe and potentially fatal disease caused by the fungus, Coccidioides immitis. This disease is rare in cats and uncommon in dogs, although dogs are more frequently affected than cats. People also are susceptible to this fungal infection.
How Valley Fever Affects Cats
Coccidioides immitis thrives in hot, arid areas of the deep southwestern United States, Mexico and parts of Central and South America. Few felines exposed to the fungus succumb to clinical disease, but unfortunately some do. Cats that spend a significant amount of time outdoors in endemic areas are obviously at increased risk. Early signs of illness tend to be nonspecific and primarily respiratory, often starting with a dry, harsh cough. Cats are especially prone to developing weeping skin sores, much more so than dogs. Other clinical signs can include anorexia, weight loss, weakness and lethargy. As the fungal infection spreads, which can take months, affected cats may develop diarrhea, vomiting, lameness (from bone involvement), swollen joints, neck or back pain, seizures, vision abnormalities, emaciation and a fever that is unresponsive to antibiotics. Why most cats are able to resist clinical infection while others develop life-threatening disease is not well understood. Once a cat is infected systemically, the prognosis is guarded to grave.
Causes of Valley Fever in Cats
Valley Fever is caused by inhalation or ingestion of infectious microorganisms released by spores of the fungus, Coccidioides immitis. In the deep southwestern areas of the United States, particularly in arid desert regions of Arizona, California and Texas and less commonly in New Mexico, Nevada and Utah, this fungus persists naturally several inches deep in the soil of endemic areas, where it can survive high temperatures and low moisture. It is dormant during periods of drought. After rainfall, earthquakes or other causes of soil disturbance (such as demolition or other large land construction projects), the fungi rise to the surface, sporulate and become airborne. Inhalation of fewer than 10 of these microorganisms can cause clinical disease. Fortunately, few cats exposed to the fungal spores succumb to clinical disease. Older and immunocompromised cats seem to be at higher risk, as do those with poor nutritional support. Valley Fever cannot be transmitted between people and cats and is not contagious between cats. When it becomes disseminated throughout the body, it is considered one of the most severe and potentially fatal fungal diseases in companion animals.
Preventing Valley Fever in Cats
This disease cannot occur unless a cat has lived in or traveled through a region where Coccidioides immitis is endemic. Contaminated soil in those areas – especially during dust or wind storms after heavy rain – should be avoided if at all possible. There is no vaccine against coccidioidomycosis for either cats or dogs.
Special Notes
Successful treatment is possible if the fungal infection is promptly and properly diagnosed, although treatment typically takes months to years to complete. Diagnosis of Valley Fever is complicated by the fact that most diagnostic laboratories regard the fungus as too dangerous to culture because of the significant risk of human infection. The prognosis for cats is not well documented. However, reports suggest that owners of clinically affected cats should be prepared for rapid systemic dissemination of the fungal infection that requires long-term treatment.
Symptoms and Types