Asymptomatic carriage of Cryptococcus neoformans in the nasal cavity of dogs and cats.

Nasal washings, obtained from a random source of dogs and cats, were concentrated by centrifugation and plated onto bird seed agar containing antibiotics. Cryptococcus neoformans var. neoformans was isolated from eight of 56 dogs (14%) and three of 45 cats (7%). More than 100 colonies of C. neoformans were present on the plates from seven of the 11 positive animals. Absence of cryptococcal antigen in the serum of these animals, and failure to demonstrate yeast-like organisms or significant pathology in nasal biopsies, suggests that the nasal cavity of these animals was not infected by C. neoformans but rather that blastoconidia and/or basidiospores were carried asymptomatically. These findings are discussed in relation to the likelihood of the upper respiratory tract being the primary site for cryptococcal infection in dogs and cats.