Coccidioidomycosis (Valley Fever)

Coccidioidomycosis, better known as Valley Fever, is caused by breathing in the spores of Coccidioides, a fungus that lives in the dry, alkaline soils of the American south-west — Arizona, California's Central Valley, New Mexico and Texas — and parts of Mexico, Central and South America. The spores lie dormant in the ground until wind, digging or construction throws them into the air, which is why outbreaks follow dust storms and the drought-then-rain cycles that let the fungus grow and then release its spores.

A cat inhales the spores and the infection usually begins in the lungs, producing a nagging cough, laboured breathing, fever and the slow, grinding weight loss of a body fighting a chronic infection. In many cats the immune system contains it there. But Coccidioides is capable of disseminating — spreading through the bloodstream to the skin, the bones and joints, and the eyes — and it is this spread that makes the disease dangerous. Non-healing sores that drain over a swelling, a new limp from infected bone, or a suddenly cloudy or blind eye are all signs the fungus has travelled.

Because the early signs are so vague, the single most useful thing an owner can do is mention where the cat lives or has travelled: Valley Fever is common knowledge to a desert vet but easily overlooked elsewhere. Diagnosis rests on blood tests for antibodies to the fungus, chest and bone imaging, and sometimes sampling a lesion.

Treatment is a marathon, not a sprint. Antifungal drugs such as itraconazole or fluconazole are given for six months to a year at least, with regular blood tests to track progress and check the liver, and the cat is only taken off medication once it is well and its fungal titre has dropped. Cats caught early and confined to the lungs often do well; those with widespread disease face a harder, sometimes lifelong course. There is no vaccine, so in endemic regions the sensible steps are to keep cats away from freshly dug, dusty soil and indoors when the wind is up.