Trichomonadida is an order of anaerobic protists, included with the parabasalids. Members of this order are referred to as trichomonads.

Quick Facts Scientific classification, Families ...

Trichomonadida
Two T. vaginalis trophozoites. Colorized SEM
Scientific classification
Domain:	Eukaryota
Phylum:	Metamonada
Subphylum:	Trichozoa
(unranked):	Parabasalia
Order:	Trichomonadida Brugerolle & Lee 2000
Families
Calonymphidae Cochlosomatidae Devescovinidae Monocercomonadidae Trichomonadidae

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Some organisms in this order include:

• Trichomonas vaginalis, an organism living inside the vagina of humans
• Dientamoeba fragilis, parasitic ameboid in humans
• Histomonas meleagridis, parasite that causes blackhead disease in poultry
• Mixotricha paradoxa, a symbiotic organism inside termites, host of endosymbionts

Species in this order typically have four to six flagella at the cell's apical pole, one of which is recurrent - that is, it runs along a surface wave, giving the aspect of an undulating membrane. Like other parabasalids, they typically have an axostyle, a pelta, a costa, and parabasal bodies. In Histomonas only one flagellum and a reduced axostyle are found, and in Dientamoeba, both are absent.

Most species are either parasites or other endosymbionts of animals.

Trichomonads reproduce by a special form of longitudinal fission, leading to large numbers of trophozoites in a relatively short time. Cysts never form, so transmission from one host to another is always based on direct contact between the sites they occupy.^[1]

The preferred treatment for trichomonad infection is Metronidazole.^[2]