An axenic culture of Giardia was established from a sample
of
infected intestine obtained following autopsy of a sulphur-crested cockatoo
(Cacatua galerita). The cockatoo recently captured in the wild
and with
good muscle tone died along with
several other cage mates, apparently of an overwhelming, acute infection
of
Giardia. Trophozoites which established in
the traditional, axenic Giardia medium (TYI-S-33 with supplementary
bile)
were morphologically identical to G.
duodenalis. When outbred Quackenbush Swiss neonatal mice were infected
with
trophozoites a chronic infection was
established and parasites were still present at 38 days post-inoculation.
Weight
gain by infected mice was reduced by 20%,
thus mimicking failure-to-thrive syndrome in children, and maximum parasite
load
was more than 3-fold higher in
comparison with other G. duodenalis strains. Analysis of the
electrophoretic karyotype, rDNA and hybridization studies
together with Giemsa- and trichrome-stained samples, and scanning electron
microscopy indicated that the bird-derived
Giardia belonged to the duodenalis group. This is the first report
of
infection of mammals with Giardia isolated from a
bird. These data may have potentially serious implications for contamination
of watersheds and establishment of zoonotic infections.