Cryptococcosis is a common infectious disease caused by the yeast-like fungus Cryptococcus neoformans. This fungus is widespread in the environment and cats (humans, dogs and other animals can also become infected) acquire it by inhaling spores. It is much more common in cats than dogs.
The organism is worldwide in distribution and is commonly found areas contaminated with bird (especially pigeon) droppings, although many infected cats have no known contact with pigeon droppings.
Immunocompromised cats such as those infected with FeLV or FIV are especially vulnerable to infections such as cryptococcosis.
Infected cats do not pose a risk to humans. Infection is acquired by inhalation of the fungus and not spread from animals or humans.
Once inhaled, the organism typically colonises in the upper respiratory tract (usually the nasal passages).