Life Cycle of Balantidium Coli

Balantidium coli are significant in that they cause an amebic intestinal infection. As single-celled organisms, they are the largest protozoan parasite, at about six-hundredths of a millimeter in length. Like many protozoa, the balantidium coli forms a cyst that hardens the cell wall and protects it as part of a survival mechanism when environmental conditions are difficult.

Features

• Unlike some protozoa, there are no insect intermediates in which the amebas are carried. The balantidia have cilia, or hair-like structures, on the surface of the cell, which makes them the only ciliated protozoa that infect human beings.

Cyst as Protection

• The ameba forms a cyst before it gets into the digestive tract so it can survive dry conditions. Additionally, the cyst helps the ameba survive the acidic conditions of the stomach until it gets to the more alkaline intestine.

Warning

• The cyst form of the balantidium may exist in water or on food that was part of someone's digestive tract; that is, food or drink that was contaminated with excrement. Balantidium may exist in pigs and other farm animals as well, so care at the time of slaughter must be taken not to cross contaminate the meat with the bowels of the pig. Someone may get a balantidium infection when an infected person does not wash his hands after using the toilet.

Growing Form

• Once inside the colon, the cyst breaks open, and the ameba takes on a form called a trophozoite. This is the eating and growing form of the ameba. The trophozoite reproduces asexually through a process called binary fission, which means the ameba reproduces then divides its genetic material as well as the cellular organelles without recombining its genetic material with another organism.

Ulcers

• Balantidia form ulcers in the colon, which can be particularly dangerous, because they may cause holes in the digestive tract and may cause a rapid bacterial infection throughout the body cavity.