Modified Ziehl-Neelsen staining and an indirect immunofluorescent assa
y appeared to be equally useful for monitoring natural infections with
Crytosporidium 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 frequent
ly positive in both species. The presence or absence of the parasite c
ould not be correlated with clinical signs or lesions and/or poor perf
ormance of the birds. Oocysts from ducklings could not be transmitted
to suckling mice but were infectious for ducklings. Oocysts from calve
s were infectious for mice but not for ducklings. These findings suppo
rt the view that mammals and birds have different Cryptosporidium spp.