E. histolytica is a single-celled protozoan that usually enters the human body when a person ingests cysts through food or water. It can also enter the body through direct contact with fecal matter. The cysts are a relatively inactive form of the parasite that can live for several months in the soil or environment where they were deposited in feces. The microscopic cysts are present in soil, fertilizer, or water that’s been contaminated with infected feces. Food handlers may transmit the cysts while preparing or handling food. Transmission is also possible during anal sex or colonic irrigation.
When cysts enter the body, they lodge in the digestive tract. They then release an invasive form of the parasite called a trophozite. The parasites reproduce in the digestive tract and migrate to the large intestine. There, they can burrow into the intestinal wall or the colon. This causes bloody diarrhea, colitis, and tissue destruction. The infected person can then spread the disease by releasing new cysts into the environment through infected feces.
Once the trophozites have breached the intestinal walls, they can enter the bloodstream and travel to various internal organs. If they invade an internal organ, they can potentially cause:
- abscesses
- infections
- severe illness
- death
