Cryptococcosis (Fungal Infection)

Cryptococcosis is the most common systemic fungal infection seen in cats. It is caused by environmental yeasts of the Cryptococcus family, which live in soil enriched by bird droppings and in association with certain trees. Cats become infected not from each other but by inhaling microscopic fungal spores from their surroundings, which is why it is more common in cats that spend time outdoors.

The infection most often takes hold first in the nasal cavity. From there it produces the disease's hallmark signs: chronic sneezing, a nasal discharge that may be thick or blood-tinged, and — as the fungal mass grows within the nose — a firm, sometimes disfiguring swelling over the bridge of the nose, giving affected cats a characteristic 'Roman nose' or a visible bump. Fungal lesions can also appear on the skin, especially around the face, as ulcerated lumps, and the lymph nodes under the jaw often enlarge.

Left untreated, cryptococcosis can spread beyond the nose — to the eyes, causing inflammation and vision problems, and in the most serious cases to the central nervous system, producing neurological signs such as circling, behavioural change, or seizures. Cats with compromised immunity, including those infected with FeLV or FIV, are more prone to this dissemination.

Diagnosis is aided by a highly useful blood test that detects cryptococcal antigen, alongside microscopic examination and culture of samples from the nose or lesions. Treatment relies on antifungal drugs given over a long period — often several months — with the antigen test used to track progress and confirm cure. It demands commitment from owners, but with sustained treatment many cats recover well, even from quite advanced infections.