Balantidium coli is a parasitic species of ciliate protozoan that causes the disease Balantidiasis.[1][2] It is the only member of the ciliate phylum known to be pathogenic to humans.[1][2]
Life cycle
Infection occurs when a host ingests a cyst, which usually happens during the consumption of contaminated water or food.[1][3] Once the cyst is ingested, it passes through the host’s digestive system.[4] While the cyst receives some protection from degradation by the acidic environment of the stomach through the use of its outer wall, it is likely to be destroyed at a pH lower than 5, allowing it to survive easier in the stomachs of malnourished individuals who have less stomach acid.[3][4] Once the cyst reaches the small intestine, trophozoites are produced.[1][4] The trophozoites then colonize the large intestine, where they live in the lumen and feed on the intestinal flora.[1][4] Some trophozoites invade the wall of the colon using proteolytic enzymes and multiply, and some of them return to the lumen.[1][3][4] In the lumen trophozoites may disintegrate or undergo encystation.[1][4] Encystation is triggered by dehydration of the intestinal contents and usually occurs in the distal large intestine, but may also occur outside of the host in feces.[1][4] Now in its mature cyst form, cysts are released into the environment where they can go on to infect a new host.[1][4]
See also
References
External links
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