Fungal Infection (Coccidioidomycosis) in Cats

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Coccidioidomycosis/Coccidioides immitis in Cats

Coccidioidomycosis, an illness caused by the Coccidioides immitis fungus, comes from inhalation of the soil-borne fungus. The respiratory system is most affected, with the fungus spores beginning in the lungs as round spherules, living in a parasitic stage there until they grow large enough to rupture, releasing hundreds of endospores. They then begin a parasitic stage in the tissues, growing and rupturing, and then disseminating into the wider body perpetually. Endospores can also take a faster route through the body by way of the lymphatic and blood vessel systems, resulting in systemic infection – meaning the entire body will be affected. Full infection sets in around 7 - 20 days after exposure, though some animals can develop an immunity and never show any symptoms, especially younger animals. Animals that are susceptible to the infection can become ill from only a small amount of the coccidioides fungus; fewer than ten fungus spores are needed to cause the disorder.

This is an uncommon but frequently deadly disease that originates mainly in the arid, hot regions of the western and southwestern regions of the U.S., and in several Central and South American countries. This infection is also known as San Joaquin Valley Fever, California Fever, cocci, and desert fever. The suffix for this disease, mycosis, is the medical term used for any disorder caused by a fungus. Coccidioidomycosis affects many mammals, including dogs, cats, and humans. However, it is not communicable between animals or humans.

Symptoms and Types

Symptoms can include:

  • Extreme weight loss and muscle wasting
  • Draining skin lesions
  • Difficulty breathing
  • Lameness
  • Inflammation of the iris and other areas in the front part of the eye.

This infection is less common in cats, and the spread of the infection tends to behave somewhat differently than with other animals. Cats typically do not show the same symptoms that dogs do, and may even remain asymptomatic until the infection has spread significantly. In cats, the deeper layers of skin tissue are more likely to be affected. Symptoms like masses, abscesses, and lesions with draining occur more often with cats.


C. immitis grows several inches deep in the upper layer of soil, where it can survive high temperatures and low moisture. The fungus returns to the surface after a period of rainfall, land construction, or crop harvest, where it forms spores that are released and spread by wind and dust storms. This fungus is found in the southwestern United States in Southern California, Arizona, southwest Texas, New Mexico, Nevada, and Utah, and in many countries in the Central and South Americas. After the rainy season, when there are dust storms, there is an increase in the number of cases.


Your veterinarian will perform a thorough physical exam on your pet, including a chemical blood profile, a complete blood count, and a urinalysis. You will need to give a thorough history of your pet's health, including a background history of symptoms, and possible incidents that might have precipitated this condition. The history you provide may give your veterinarian clues as to which organs are being affected secondarily.

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