Balantidium coli

 

·       The only pathogenic ciliate protozoan of humans. It is the largest protozoan parasite of humans. It is present worldwide, but the prevalence of the infection is very low.

·        More common where pigs reared and pigs faeces used as fertilizer in warmer climates.

·        Habitat – trophozoite & cyst in large intestine of pig and rarely man.

·       B. coli occur in two stages - the trophozoite and cyst.

1. Trophozoite

• Oval, with one pole more rounded than the other.

·        Rapid motility using the cilia, crossing the field in a definite direction and sometimes turning in circle.

o   Cover the whole body and longer around the cytostome called adoral cilia.

·        One large kidney-shaped macronucleus and one small micronucleus.

·        Cytostome: a sort of mouth that contracts and expands to draw in debris. The anterior end is narrow and the posterior broad. The anterior end is pointed and has a groove (peristome) leading to the mouth (cytostome) terminating in a short funnel-shaped gullet (cytopharynx).

·        The posterior end is broadly rounded and has a small an excretory pore (cytopyge).

§  Cyst

• It is the infective stage. Shape:  round or spherical. Shell:  thick double-layered wall
• Nucleus:  similar to the trophozoite. Cilia: inside wall, sometimes can be seen in younger or newly formed cysts. The contractile vacuoles are present in the cysts also.

v Transmission

§  Through ingestion of contaminated food or water as well as hands contaminated with pig faeces containing cyst.-Faecal-oral-route transmission.

v Life cycle

·        Man most often acquires the cysts through ingestion of contaminated food or water.

·        Excystation occurs in the small intestine. From each cyst, a single trohpozoite is formed and the liberated trophozoites colonize the large intestine.

·        The trophozoites reside in the lumen of the large intestine of humans and multiply by binary fission, or conjugation may occur.Conjugation occurs infrequently, during which reciprocal exchange of nuclear material takes place between two trophozoites. Conjugation is sexual fusion of two cells which is an important aspect of this parasite in its life cycle.

·        Encystation occurs as the trophozoites passes down the colon to produce infective cysts.

·        Mature cysts are passed with faeces.

 

v Clinical features

·       Clinical manifestations, when present, include persistent diarrhea, constipation, occasionally dysentery with blood & mucus, abdominal pain, nausea, vomiting, intestinal colic, and weight loss.

v Diagnosis

·        Diagnosis is based on detection of the parasite in stool specimens.

·        Generally, B. coli  is easy to recognize in stool specimens during microscopic examination due to: Its large kidney-shaped macronucleus.; Its large size. And Its cilia which covered the outer membrane.

v Prevention and control

·       Avoidance of contamination of food and water with human or animal faeces containing cysts.

·       Keep personal hygiene especially those who keep pigs. And Treatment & health education.