Natural infections by Cryptosporidium sp. in farm-raised ducks and geese.

Modified Ziehl-Neelsen staining and an indirect immunofluorescent assay appeared to be equally useful for monitoring natural infections with Cryptosporidium sp. in farm-raised Pekin ducklings and Danish goslings. In 73 of 128 ducklings, and in 44 of 74 goslings, Cryptosporidium sp. were detected. Tissues from the bursa of Fabricius are most frequently positive in both species. The presence or absence of the parasite could not be correlated with clinical signs or lesions and/or poor performance of the birds. Oocysts from ducklings could not be transmitted to suckling mice but were infectious for ducklings. Oocysts from calves were infectious for mice but not for ducklings. These findings support the view that mammals and birds have different Cryptosporidium spp.