Excystation occurs within 5 minutes of exposure of the cysts to an environment with a pH between 1.3 and 2.7. After infection, the trophozoites attach to the enterocytes via the ventral adhesive disk. This may occur through the presence of lectin on the surface of the trophozoite or through other mechanical means.

Where does Excystation take place?

Excystation (3) occurs in the small intestine and trophozoites (4) are released, which migrate to the large intestine. The trophozoites multiply by binary fission and produce cysts (5), and both stages are passed in the feces (1).

What causes Excystment to occur?

Following ingestion by a new host, the cyst is exposed to the various biochemicals found in the upper gastrointestinal (GI) tract, which results in the eventual emergence (excystment) of the ameboid trophozoite form via a process that is assumed to occur in the small intestine.