Balantidium coli Overview

Balantidium coli

• Resides in the large intestine of humans, pigs, and monkeys.
• Trophozoite is the active, invasive stage found in dysenteric stool.
  • Large, ovoid cell measuring 60-70 µm in length and 40-50 µm in breadth.
  • Enclosed in a delicate pellicle with longitudinal striations.
  • Motility is driven by short, delicate cilia covering the entire surface.
  • Anterior end is narrow, posterior end is broad.
  • Peristome (groove) leading to the mouth (cytostome) and a short, funnel-shaped gullet (cytopharynx) at the anterior end.
  • Small anal pore (cytopyge) at the posterior end.
  • Larger cilia (adoral cilia) surround the mouth.
  • Two nuclei: a large, kidney-shaped macronucleus and a smaller micronucleus located within its concavity.
  • Cytoplasm contains one or two contractile vacuoles and several food vacuoles.
• Cyst is the spherical infective stage measuring 40-60 µm in diameter.
  • Surrounded by a thick, transparent double-layered wall.
  • Granular cytoplasm containing macronucleus, micronucleus, and vacuoles.
  • Found in chronic cases and carriers.

Transmission

• Zoonosis: Humans acquire infection by ingesting food and water contaminated with feces containing B. coli cysts.
• Infection acquired from pigs, other animal reservoirs, or human carriers.

Life Cycle

• Monoxenous: Completes its life cycle in a single host.
• Natural host: Pig.
• Accidental host: Human.
• Reservoirs: Pig, monkey, and rat.
• Infective form: Cyst.
• Cyst ingested and undergoes excystation in the small intestine.
• Single trophozoite is released from each cyst and migrates to the large intestine.
• Trophozoites multiply by transverse binary fission in the large intestine.
• Infrequent sexual union (conjugation) occurs with reciprocal exchange of nuclear material between two trophozoites enclosed within a single cyst wall.
• Encystation occurs as the trophozoite passes down the colon or is evacuated in stool.
• Cell rounds up and secretes a tough cyst wall around it.
• Cysts remain viable in feces for one to two days and can contaminate food and water, transmitting the infection to humans or animals.

Pathogenesis

• Clinical disease only occurs when host resistance is lowered by predisposing factors such as malnutrition, alcoholism, achlorhydria, co-infection with Trichuris trichiura, or bacterial infections.
• Trophozoites burrow into the intestinal mucosa, form colonies, and initiate inflammatory reactions.
• Leads to mucosal ulcers and submucosal abscesses resembling lesions in amoebiasis.
• B. coli does not invade the liver or other extraintestinal sites, unlike Entamoeba histolytica.

Clinical Features

• Balantidiasis (symptomatic disease) resembles amoebiasis, causing diarrhea or dysentery with abdominal colic, tenesmus, nausea, and vomiting.
• Balantidium ulcers may be secondarily infected by bacteria.
• Intestinal perforation, peritonitis, and even death may occur in rare cases.
• Involvement of genital and urinary tracts is uncommon.
• Chronic balantidiasis presents with alternating diarrhea and constipation.

Laboratory Diagnosis

• Stool Examination: Demonstration of trophozoites and cysts in feces (trophozoites in diarrheic feces, cysts in formed stools).
• Biopsy: When stool examination is negative.
• Culture: B. coli can be cultured in vitro using Locke’s egg albumin medium or NIH polyxenic medium, similar to Entamoeba histolytica.

Treatment

• Tetracycline: Drug of choice, 500 mg four times daily for ten days.
• Doxycycline: Alternative treatment.
• Metronidazole and Nitroimidazoles: Reported to be effective in some cases.

Prophylaxis

• Avoid contamination of food and water with human or animal feces.
• Prevent human-pig contact.
• Treat infected pigs.
• Treat individuals shedding B. coli cysts.

Balantidium coli

• Habitat: Large intestine of humans, pigs, and monkeys.
• Trophozoite:
  • Actively motile, invasive stage found in dysenteric stool.
  • Large ovoid cell, about 60–70 μm long and 40–50 μm wide.
  • Covered in cilia for motility.
  • Anterior end is narrow, posterior end is broad.
  • Has a groove leading to the mouth (cytostome) and a short, funnel-shaped gullet (cytopharynx).
  • Contains a large kidney-shaped macronucleus and a small micronucleus.
  • Contains 1 to 2 contractile vacuoles and several food vacuoles.
• Cyst:
  • Spherical, 40–60 μm in diameter.
  • Surrounded by a thick, transparent double-layered wall.
  • Contains macronucleus, micronucleus, and vacuoles.
  • Infective stage, found in chronic cases and carriers.
• Mode of Transmission:
  • Zoonosis, acquired through ingestion of food and water contaminated with feces containing cysts.
  • Transmission from pigs, other animal reservoirs, or human carriers.
• Life Cycle:
  • Monoxenous (one host).
  • Natural host: Pig.
  • Accidental host: Human.
  • Reservoirs: Pig, monkey, and rat.
  • Infective form: Cyst.
  • Cyst ingestion leads to excystation in the small intestine, releasing a trophozoite.
  • Trophozoite migrates to the large intestine and multiplies by transverse binary fission.
  • Infrequent conjugation (sexual union) may occur, with reciprocal exchange of nuclear material.
  • Encystation occurs during passage through the colon or in evacuated stool.
  • Cysts remain viable for 1-2 days and can contaminate food and water, allowing transmission to other humans and animals.
• Pathogenesis:
  • Clinical disease occurs when host resistance is lowered by factors like malnourishment, alcoholism, achlorhydria, concurrent infections, or bacterial infections.
  • Trophozoites invade the intestinal mucosa, forming colonies and initiating inflammation.
  • This leads to mucosal ulcers and submucosal abscesses, similar to amoebiasis.
  • Unlike E. histolytica, B. coli does not invade the liver or other extraintestinal sites.
• Clinical Features:
  • Balantidiasis resembles amoebiasis, causing diarrhea or dysentery with abdominal colic, tenesmus, nausea, and vomiting.
  • Balantidium ulcers can be secondarily infected by bacteria.
  • Intestinal perforation, peritonitis, and death can occur in rare cases.
  • Genital and urinary tract involvement is uncommon.
  • Chronic balantidiasis features alternating diarrhea and constipation.
• Laboratory Diagnosis:
  • Stool examination: Demonstration of trophozoites (diarrheic stool) and cysts (formed stool).
  • Biopsy: When stool examination is negative.
  • Culture: B. coli can be cultured in vitro in Locke's egg albumin medium or NIH polyxenic medium.
• Treatment:
  • Tetracycline (500 mg, 4 times daily for 10 days) is the drug of choice.
  • Doxycycline is an alternative.
  • Metronidazole and nitroimidazoles have also been reported as effective in some cases.
• Prophylaxis:
  • Avoid contamination of food and water with human or animal feces.
  • Prevent human-pig contact.
  • Treat infected pigs.
  • Treat individuals shedding B. coli cysts.

Balantidium coli

• Balantidium coli is a protozoan parasite that resides in the large intestine of humans, pigs and monkeys.
• The trophozoite is the actively motile and invasive stage of the parasite, found in dysenteric stool.
• It is a large cell (60-70 µm in length, 40-50 µm in breadth) enclosed in a delicate pellicle with longitudinal striations.
• Motility is due to cilia covering the entire surface of the cell.
• The anterior end is narrow, the posterior end broad.
• The anterior end features a groove called the peristome, leading to the mouth (cytostome), and a short funnelshaped gullet (cytopharynx).
• The posterior end houses a small anal pore (cytopyge).
• The cilia situated around the mouth are larger and are referred to as adorai cilia.
• The cell is characterized by two nuclei: a large kidney-shaped macronucleus and a small micronucleus positioned within its concavity.
• The cytoplasm contains one or two contractile vacuoles and several food vacuoles.

Cyst

• The cyst is spherical (40-60 µm in diameter).
• It has a thick, transparent, double-layered wall.
• The cyst is the infective stage of B. coli and is found in chronic cases and carriers.

Mode of Transmission

• Balantidiasis is a zoonotic infection.
• Humans acquire infection through ingestion of contaminated food and water containing cysts.
• Infection can be acquired from pigs and other animal reservoirs or from human carriers.

Life Cycle

• B. coli completes its life cycle in a single host (monoxenous).
• Natural host: Pig.
• Accidental host: Man.
• Reservoirs: Pig, monkey, and rat.
• Infective form: Cyst.
• After ingestion, excystation occurs in the small intestine, releasing a single trophozoite.
• The trophozoite then migrates to the large intestine.
• Liberated trophozoites multiply in the large intestine by transverse binary fission.
• Sexual union (conjugation) occurs infrequently, with reciprocal exchange of nuclear material between two trophozoites within a single cyst wall.
• Encystation occurs as the trophozoite traverses the colon or is evacuated in the stool.
• The cell rounds up, secreting a tough cyst wall around it.
• Cysts remain viable in feces for one to two days and can contaminate food and water, leading to transmission to other humans or animals.

Pathogenesis

• Clinical disease develops when the host's resistance is lowered by predisposing factors such as malnourishment, alcoholism, achlorhydria, concurrent infection with Trichuris trichiura, or bacterial infection.
• Trophozoites burrow into the intestinal mucosa, forming colonies and triggering inflammatory reactions.
• This leads to mucosal ulcers and submucosal abscesses, resembling the lesions seen in amoebiasis.
• Unlike Entamoeba histolytica, B. coli does not invade the liver or other extraintestinal sites.

Clinical Features

• Symptomatic disease or balantidiasis resembles amoebiasis, characterized by diarrhea or dysentery, abdominal colic, tenesmus, nausea, and vomiting.
• Balantidium ulcers may be secondarily infected by bacteria.
• Intestinal perforation, peritonitis, and even death can occur, although these complications are relatively rare.
• Involvement of the genital and urinary tracts may occur, though this is uncommon.
• In chronic balantidiasis, patients experience diarrhea alternating with constipation.

Laboratory Diagnosis

• Stool examination: Demonstration of trophozoites and cysts in feces (trophozoites in diarrheic feces, cysts in formed stools).
• Biopsy: When stool examination is negative.
• Culture: Similar to Entamoeba histolytica, B. coli can be cultured in vitro in Locke's egg albumin medium or NIH polyxenic medium.

Treatment

• Tetracycline is the drug of choice, administered at 500 mg four times daily for 10 days.
• Alternatively, Doxycycline can be used.
• Metronidazole and nitroimidazoles have also been found to be helpful in some cases.

Prophylaxis

• Avoid contamination of food and water with human or animal feces.
• Prevent human-pig contact.
• Treat infected pigs.
• Treat individuals shedding B. coli cysts.

Balantidium coli

• Habitat: Large intestine of humans, pigs, and monkeys.
• Trophozoite: Actively motile and invasive stage found in dysenteric stool.
  • Large ovoid cell (60–70 μm length, 40–50 μm breadth).
  • Enclosed in a delicate pellicle with longitudinal striations.
  • Moves using cilia on its surface.
  • Anterior end is narrow, posterior end is broad.
  • Peristome: Groove leading to the mouth (cytostome).
  • Cytopharynx: Short funnel-shaped gullet.
  • Cytopyge: Small anal pore.
  • Adoral cilia: Larger cilia around the mouth.
  • Nuclei: One large kidney-shaped macronucleus and one small micronucleus.
  • Cytoplasm: Contains one or two contractile vacuoles and several food vacuoles.
• Cyst: Spherical shape, 40–60 μm in diameter.
  • Surrounded by a thick double-layered wall.
  • Contains a granular cytoplasm, macronucleus, micronucleus, and vacuoles.
  • Infective stage of B.coli.
  • Found in chronic cases and carriers.

Transmission and Life Cycle

• Zoonosis: Humans acquire infection through ingestion of food and water contaminated with feces containing cysts.
• Reservoirs: Pigs, monkeys, and rats.
• Infective Form: Cyst.
• Monoxenous: The parasite completes its life cycle in a single host.
  • Natural host: Pig.
  • Accidental host: Human.
• Life Cycle:
  • Cyst ingestion leads to excystation in the small intestine.
  • One trophozoite emerges from each cyst and migrates to the large intestine.
  • Trophozoites multiply in the large intestine by transverse binary fission.
  • Conjugation: Sexual union occurs infrequently where two trophozoites exchange nuclear material within a single cyst wall.
  • Encystation: Occurs as the trophozoite moves through the colon or in evacuated stool.
  • Cell rounds up and secretes a tough cyst wall.
  • Cysts can remain viable in feces for 1-2 days, contaminating food and water, and transmitting the infection.

Pathogenesis

• Clinical disease: Occurs when host resistance is lowered (malnourishment, alcoholism, achlorhydria, concurrent infections).
• Trophozoites: Burrow into the intestinal mucosa, form colonies, and cause inflammatory response.
• Ulcers and abscesses: Resulting lesions resemble those in amoebiasis.
• Extraintestinal Invasion: Unlike E. histolytica, B.coli does not invade the liver or other organs.

Clinical Features

• Balantidiasis: Resembles amoebiasis.
• Symptoms: Diarrhea or dysentery, abdominal colic, tenesmus, nausea, vomiting.
• Bacterial Infections: Balantidium ulcers can be secondarily infected by bacteria.
• Complications: Intestinal perforation, peritonitis, death.
• Genital and Urinary Tracts: Involvement is rare.
• Chronic Balantidiasis: Diarrhea alternating with constipation.

Laboratory Diagnosis

• Stool Examination: Demonstration of trophozoites and cysts in feces (trophozoites in diarrheic feces, cysts in formed stools ).
• Biopsy: When stool examination is negative.
• Culture: B.coli can be cultured in vitro using media similar to that for Entamoeba histolytica.

Treatment

• Drug of Choice: Tetracycline (500 mg, 4 times daily for 10 days).
• Alternatives: Doxycycline, metronidazole, nitroimidazoles.

Prophylaxis

• Prevention of Contamination: Avoid contamination of food and water with human or animal feces.
• Human-Pig Contact: Prevent human-pig contact.
• Treatment of Infected Pigs and Carriers: Treat infected pigs and individuals shedding B.coli cysts.

Balantidium Coli

• Habitat: Large intestine of humans, pigs, and monkeys.
• Trophozoite:
  • Actively motile, invasive stage of the parasite.
  • Found in dysenteric stool.
  • Large ovoid cell (60–70 μm long, 40–50 μm wide).
  • Encased in a delicate pellicle with longitudinal striations.
  • Motility due to short, delicate cilia covering the cell surface.
  • Narrow anterior end, broad posterior end.
  • Anterior End:
    • Peristome: Groove leading to the mouth (cytostome).
    • Cytopharynx: Short, funnel-shaped gullet.
  • Posterior End: Small anal pore (cytopyge).
  • Cilia: Larger around the mouth (adoral cilia).
  • Nuclei:
    • Large, kidney-shaped macronucleus.
    • Small micronucleus within the macronucleus' concavity.
  • Cytoplasm:
    • 1-2 contractile vacuoles.
    • Multiple food vacuoles.
• Cyst:
  • Spherical shape (40–60 μm in diameter).
  • Thick, transparent, double-layered wall.
  • Granular cytoplasm.
  • Contains macronucleus, micronucleus, and vacuoles.
  • Infective stage of B. coli, found in chronic cases and carriers.
• Transmission:
  • Zoonosis (transmitted from animals to humans).
  • Humans acquire infection by ingesting food and water contaminated with feces containing B. coli cysts.
  • Infection sources include pigs, other animal reservoirs, or human carriers.
• Life Cycle:
  • Monoxenous (passes its life cycle in one host).
    • Natural host: Pig.
    • Accidental host: Human.
    • Reservoirs: Pigs, monkeys, and rats.
  • Infective form: Cyst.
  • Cyst Ingestion:
    • Excystation occurs in the small intestine releasing a single trophozoite.
  • Trophozoite Migration:
    • Trophozoite migrates to the large intestine.
  • Multiplication:
    • Trophozoites multiply in the large intestine via transverse binary fission.
  • Conjugation:
    • Infrequent sexual union with reciprocal exchange of nuclear material between two trophozoites enclosed within a single cyst wall.
  • Encystation:
    • Occurs as the trophozoite passes down the colon or in evacuated stool.
    • Trophozoite rounds up and secretes a tough cyst wall.
    • Cysts remain viable in feces for 1-2 days, contaminating food and water, and transmitting to other humans or animals.
• Pathogenesis:
  • Clinical disease occurs when host resistance is lowered by factors like:
    • Malnourishment.
    • Alcoholism.
    • Achlorhydria.
    • Concurrent infection with Trichuris trichiura.
    • Bacterial infections.
  • Trophozoites burrow into the intestinal mucosa, establishing colonies and triggering an inflammatory reaction.
  • This leads to mucosal ulcers and submucosal abscesses, similar to lesions seen in amoebiasis.
  • Unlike E. histolytica, B. coli doesn't invade the liver or other extraintestinal sites.
• Clinical Features:
  • Symptomatic disease (balantidiasis) resembles amoebiasis.
  • Causes diarrhea or dysentery with:
    • Abdominal colic.
    • Tenesmus.
    • Nausea.
    • Vomiting.
  • Balantidium ulcers may be secondarily infected by bacteria.
  • Occasionally, intestinal perforation, peritonitis, and even death can occur.
  • In rare cases, the genital and urinary tracts may be involved.
  • Chronic balantidiasis presents with alternating diarrhea and constipation.
• Laboratory Diagnosis:
  • Stool Examination:
    • Demonstration of trophozoites and cysts in feces.
      • Trophozoites found in diarrheic feces.
      • Cysts found in formed stools.
  • Biopsy: When stool examination is negative.
  • Culture:
    • Similar to Entamoeba histolytica, B. coli can be cultured in vitro using Locke's egg albumin medium or NIH polyxenic medium.
• Treatment:
  • Drug of Choice: Tetracycline (500 mg, 4 times daily for 10 days).
  • Alternative: Doxycycline.
  • Other Effective Treatments: Metronidazole and nitroimidazole.
• Prophylaxis:
  • Avoid contamination of food and water with human or animal feces.
  • Prevent human-pig contact.
  • Treat infected pigs.
  • Treat individuals shedding B. coli cysts.

Explore the fascinating organism Balantidium coli, which resides in the intestines of humans and various animals. This quiz covers its structure, life cycle, and distinguishing characteristics, including motility, nuclei, and reproductive stages. Ideal for students of microbiology or parasitology.