Centers for Disease Control/Division of Parasitic Diseases and Malaria
EOL staff
Life cycle of Trichomonas vaginalis, the cause of trichomoniasis in humansTrichomonas vaginalis resides in the female lower genital tract and the male urethra and prostate (1), where it replicates by binary fission (2). The parasite does not appear to have a cyst form, and does not survive well in the external environment. Trichomonas vaginalis is transmitted among humans, its only known host, primarily by sexual intercourse (3).From Centers for Disease Control Parasites and Health website
Centers for Disease Control/Division of Parasitic Diseases and Malaria
EOL staff
Life cycle of Chilomastix mesnili The resistant cyst stage in the life cycle of Chilomastix is responsible for transmission. Both cysts and trophozoites can be found in the feces (diagnostic stages) (1). Infection occurs by the ingestion of cysts in contaminated water or food or by the fecal-oral route (via hands or fomites, i.e., inanimate objects such as towels that transmit infectious organisms to a host) (2). In the large (and possibly small) intestine, excystation releases trophozoites.From Centers for Disease Control Parasites and Health website.
Centers for Disease Control/Division of Parasitic Diseases and Malaria
EOL staff
Life cycle of Enteromonas hominisBoth cysts (dormant stage) and trophozoites (active stage) of Enteromonas hominis are shed in feces. Infection occurs after the ingestion of cysts in fecal-contaminated food or water, or on fomites (inanimate objects or substances capable of transferring pathogens). In the large (and possibly small) intestine, excystation releases trophozoites. Enteromonas hominis resides in the large intestine, where it is regarded as a commensal (benefiting from its host but doing no harm) and is not known to cause disease.FromCenters for Disease Control Parasites and Health website.
Centers for Disease Control/Division of Parasitic Diseases and Malaria
EOL staff
Life cycle of the flagellate Pentatrichomonas hominisPentatrichomonas hominis is a trichomonad flagellate with a worldwide distribution. Only trophozoites are shed in feces (1) as there is no known cyst stage for this species. Infection occurs after the ingestion of trophozoites in fecally-contaminated food or water or on fomites (i.e., other non-living objects or substances that can transmit them) (2). These organisms reside in the large intestine, where they are regarded as commensals (i.e., benefiting from but not harming their host) and are not known to cause disease in humans.From Centers for Disease Control Parasites and Health website