Which fungal infection is associated with immunosuppression and is transmitted through pigeon droppings?

The fungal infection strongly associated with immunosuppression and transmitted through pigeon droppings is Cryptococcus. This organism, particularly Cryptococcus neoformans, is a significant pathogen in individuals with a weakened immune system, such as those with HIV/AIDS or those undergoing immunosuppressive therapy.

Cryptococcus is typically acquired through inhalation of spores found in the environment, often concentrated in areas where birds, particularly pigeons, roost. The organism can cause meningitis and encephalitis, particularly in immunocompromised individuals, leading to severe neurological symptoms. In those with a robust immune system, the infection might resolve without causing significant disease, but in high-risk populations, the consequences can be severe.

While Histoplasmosis and Blastomycosis are important fungal infections with their own associations, Histoplasmosis is primarily linked with bat droppings and areas rich in soil, while Blastomycosis is associated with decaying organic matter in certain geographic areas. Candidiasis, on the other hand, is caused by Candida species and is usually part of the normal flora, leading to opportunistic infections rather than being directly transmitted through the environment in the same way as Cryptococcus.