Diagnostic Parasitology

 Balantidium coli
Due to its large size, Balantidium coli is one of the easier intestinal protozoa to identify. The cyst, top left, measures about 50 to 70 µm in diameter.  The parasite is characterized by the presence of a large kidney-shaped macronucleus. The image at right is an unstained wet mount of a cyst (courtesy of Gustavo Gini).
The trophozoite is oval and measures approximately 50 to 100 µm long and 40 to 70 µm wide. Balantidium coli is the only pathogenic ciliate. The image on the left was taken at 400x. In the image on the right, the cytostome is visible (arrow), image courtesy Gustavo Gini.

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Copyright 2008 Don Lehman