Fungal infections, a rare cause of disease in cats, affect about 7 out of every 10,000 cats seen at veterinary teaching hospitals in North America. However, in certain geographic regions, fungal disease can be much more prevalent in the feline population.
Cats acquire most fungal infections by inhaling infectious organisms in the environment, but they are not considered zoonotic or communicable. This means that although the diseases described below are technically infectious diseases, a cat with fungal disease cannot spread the illness to any other pets or humans, though both may be at risk if they encounter the same environmental fungal source.
Cryptococcosis is the most common systemic fungal disease found in cats, and is most often seen along the Pacific coast of North America, as well as in many parts of Europe and Australia. Disease is caused when a cat inhales the infectious spores of the fungal Cryptococcus neoformans - Cryptococcus gattii species complex. These spores are most often found in bird droppings, especially pigeon feces, but can also be found in decaying vegetation. Cats are much more likely than other domestic animals to be affected by cryptococcosis, and both indoor and outdoor cats are susceptible to the disease.
As Cryptococcus is an airborne pathogen, the nasal cavity is the primary source of infection for cats, but the disease can spread throughout the body from there. There are four forms of feline cryptococcosis - nasal, nervous system, cutaneous (skin), and systemic. The nasal form is the most common, and characterized by chronic nasal discharge, sneezing, loud breathing, swelling of the nose and face, deep non-healing wounds on the hose, or even visible masses or polyps in the nasal cavity. Nasal cryptococcosis can lead to difficulty breathing, weight loss, loss of appetite, or problems with a cat’s ears and balance. Central nervous system (CNS) cryptococcosis usually occurs when the nasal form spreads back behind the nasal cavity into a cat’s brain. Cats with the CNS form of the disease can be affected by sudden blindness, seizures, behavioral changes, and head or spinal pain. Cats with cutaneous cryptococcosis show single or multiple non-painful, non-itchy nodules on or right below their skin, and may have lymph node enlargement. Systemic cryptococcosis occurs when the infection spreads through the bloodstream, and can involve changes to the eyes and bones, joint inflammation, and multi-organ system disease. Lethargy and anorexia are common in cats suffering from prolonged systemic cryptococcosis.
Feline cryptococcosis can often be diagnosed through an antigen detection test, known as a Latex Agglutination Test (LAT), on a cat’s blood, urine, or cerebrospinal fluid. In certain cases with localized disease, such as nasal or cutaneous disease, the blood test may be negative even when cryptococcosis is suspected. In these instances, tissue samples can be taken to look for evidence of fungal segments under a microscope. Prognosis for recovery from the disease is generally favorable with early treatment and good follow-up, though nervous system involvement can make the likelihood of recovery lower. Treatment involves prolonged oral antifungal therapy, which can last many months, as well as surgical excision of any skin lesions. Treatment should be continued until the LAT is negative, or for 2-4 months past the resolution of any clinical signs.
Last updated 2021