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Non-pathogenic flagellates

There are a number of other flagellates found in humans that do not appear to cause disease. Trichomonas hominis is commonly found in faeces of individuals living in the developing world. Only the trophozoite form is recognized; it varies from 5 to 14 mm in length. There is a single nucleus, anterior to which are basal bodies from which arise three to four flagella.

Chilomastix mesnili occurs as both cysts and trophozoite and is larger than Trichomonas hominis, being usually 10–15 mm in length, although it may occasionally be as large as 20 mm. The trophozoite has a large spiral longitudinal cleft anteriorly and an anterior single nucleus. Basal bodies at the anterior pole of the nucleus give rise to three anterior flagella, two fibrils that support the margins of the longitudinal cleft (the mouth), and a fourth flagellum, which moves within the longitudinal cleft. There are no cytoskeletal elements, the parasite maintaining its shape by a pellicle. The cyst is …