Severe pulmonary infections in man may be caused by exposure to infected birds or their droppings. Ornithosis, histoplasmosis and cryptococcosis develop as a result of inhalation of an infective agent. Pigeon-breeder's lung is an allergic alveolitis caused by a hypersensitivity reaction to avian droppings or feathers. This condition is recurrent and is best treated by avoidance of further exposure. Corticosteroids are useful in acute cases.
