Encystation of entamoeba parasites.

Entamoeba histolytica is a protozoan parasite of humans, and the causitive agent of intestinal amebiasis. The disease-causing stage of the parasite is an osmotically sensitive ameboid form, which differentiates into a thick-walled cyst for transmission from person to person. The conditions within the human intestine that induce encystment of the amoeba are unknown, but studies using an amoebic parasite of reptiles are now yielding information about the molecules and host:parasite interactions involved in the process. An understanding of the amoeba's obligatory encystment pathway should provide an approach for interrupting the transmission of this parasite, for which there is currently no vaccine.