Cryptococcus neoformans in the respiratory tract of squirrels, Callosciurus finlaysonii (Rodentia, Sciuridae)

Cryptococcosis is a fungal disease acquired from the environment, for which animals may serve as sentinels for human exposure. The occurrence of Cryptococcus spp. in the respiratory tract of 125 squirrels, Callosciurus finlaysonii, trapped in Southern Italy, was assessed. Upon examination of nasal swabs and lung tissue from each individual, a total of 13 (10.4%) animals scored positive for yeasts, 7 for Cryptococcus neoformans (C.n.) (5.6%) and 6 for other yeasts (4.8%). C.n. was isolated from the nostrils and lungs, with a high population size in nostrils. Two C.n. molecular types, VNI and VNIV, were identified, with C.n. var. grubii VNI the most prevalent. Phylogenetic analyses of ITS+ and URA5 sequences revealed that C.n. isolates were genetically similar to isolates from a range of geographical areas and hosts. Results suggest that C.n. can colonize or infect the respiratory tract of C. finlaysonii. The high occurrence and level of colonization of nasal cavities might be an indicator of environmental exposure to high levels of airborne microorganism. The close phylogenetic relationship of C.n. strains from squirrels with those from human and other animal hosts suggests a potential role for these animals as "sentinels" for human exposure.