The Parasite: Balantidium coli
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Balantidium coli is the only ciliate known to parasitize
humans. Ciliates represent a phylum
of protozoa characterized, in at least one stage of development, by simple or
compound ciliary organelles on the surface of their membranes that are used
for locomotion. Ciliates have 2
nuclei (one macronucleus and one micronucleus) and reproduce by transverse
binary fission, conjugation, autogamy, and cytogamy. Balantidium coli has 2 contractile vacuoles. Although contractile vacuoles are common
to ciliates, they are rare in parasitic protozoa, which suggests that Balantidium
coli has a unique osmoregulatory capacity. Balantidium coli has 2 developmental stages: a
trophozoite stage and a cyst stage. (See Morphology
and Life Cycle for descriptions of the stages.) |
Taxonomy Kingdom – Protista Phylum
– Ciliophora Class
– Litostomatea Order
– Vestibuliferida Balantidium coli
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History
Balantidium coli has been known for more than a century,
and yet the pathogenicity of the protozoa and how humans acquire it are still
not fully understood.
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