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Balantidiasis - Causes, Signs and Symptoms, Diagnosis, Treatment, and Prevention

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Balantidiasis - Causes, Signs and Symptoms, Diagnosis, Treatment, and Prevention

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Balantidiasis is a rare bacterial infection caused by a parasite called Balantidium coli. Read the article below to know more about the infection.

Written by

Dr. P. Saranya

Medically reviewed by

Dr. Kaushal Bhavsar

Published At August 8, 2022
Reviewed AtMay 31, 2024


A parasite is a living organism that lives in or on another organism and gets its nutrition from it. Balantidium coli is a protozoan (single-celled) parasite of the intestine that can infect humans. Balantidium coli is the largest and only protozoan, having cilia or hair-like structures capable of causing disease in humans. These parasites are primarily transmitted through contaminated food and water through the fecal-oral route. Balantidium coli infections often present with no symptoms, but people with other serious illnesses can have persistent diarrhea and abdominal pain. Balantidiasis is an infection of the digestive system affecting the large intestine. Balantidiasis is also known as balantidiasis or ciliary dysentery. Balantidiasis coli is uncommonly reported but has a worldwide distribution. Many mammal species serve as hosts for Balantidium coli. Still, pigs remain the common reservoir for human infection, and human cases are more common in areas that engage in pig farming.

What Causes Balantidiasis?

Balantidiasis is a rare intestinal infectious disease caused by the single-celled parasite Balantidium coli. This parasite may be transmitted directly to humans by contact with pig feces or indirectly by drinking contaminated water or food. Poor nutrition, a weak immune system, or other illness may cause severe symptoms. Balantidiasis affects males and females in equal numbers.

Infection with Balantidium coli is caused in the following ways:

  • Directly by eating foods (meat, fruits, and vegetables) contaminated by an infected person or indirectly from the fecal matter of an infected animal (pig).

  • Drinking and washing the food with water that is contaminated by the infected person or infected animal.

  • Having poor sanitation.

Other factors that can predispose to Balantidium coli infection are:

  • Alcoholism.

  • The number of infecting parasites.

  • The normal bacterial status in the intestine.

  • Presence of cancer like abdominal lymphoma.

  • Nutritional insufficiency.

What Are the Stages of the Life Cycle of Balantidium Coli?

Balantidium coli is a sizable ciliated protozoan with a life cycle consisting of four stages: cysts, trophozoite, binary fission, and encystation. The initial stage, cysts, marks the transmission of balantidiasis disease. Subsequently, there is an intermediate phase during which the cyst attains infectivity. Transmission of B. coli typically occurs orally, as the host ingests the infectious cysts through contaminated food or water.

Upon ingestion, excystation takes place in the small intestine, leading to colonization of the large intestine by trophozoites. These trophozoites undergo binary fission in the human or animal intestinal lumen (specifically, the appendix and large intestines) where they reside. Encystation follows, allowing trophozoites to transform into infective cysts. Mature cysts are eventually excreted in feces.

What Is the Pathophysiology of Balantidiasis?

Balantidium coli presents in two forms, trophozoite, and cyst, typically impacting the large intestine, spanning from the caecum to the rectum. Trophozoites undergo replication through binary fission and conjugation, thriving on bacteria. Upon ingestion by humans, infective cysts migrate to the large intestine, cecum, and terminal ileum. While predominantly inhabiting the intestinal lumen, these organisms can also penetrate the mucosa, leading to ulcer formation.

The invasion of the intestinal mucosa is facilitated by several mechanisms:

  • Mechanical action is attributed to the ciliary movements of trophozoites.

  • Production of hyaluronidase (an enzyme that breaks down hyaluronic acid) is crucial for maintaining the cohesion of mucosal epithelial cells.

  • Production of proteolytic enzymes by the parasite, which assists in tissue invasion and potential perforation.

How Does the Infection Occur?

During its life cycle, Balantidium coli exists in two different forms: the infective cyst form, which cannot move but can survive outside the human body, and the disease-producing form, the trophozoite, which is capable of moving but cannot survive once excreted in the feces. The walls of the cysts are broken in the intestine, and they release the mobile trophozoites. Once released in the intestine, the trophozoites multiply by feeding on intestinal bacteria or invading the large intestine lining. The trophozoites secrete a substance that destroys the intestinal lining and creates ulcers or abscesses. Trophozoites form new cysts carried through the digestive tract and excreted in the feces. The cysts can survive in the soil or water for weeks to months, transmitting infection.

What Are the Signs and Symptoms?

Most people with balantidiasis have no symptoms or present with mild symptoms. Even though the asymptomatic individuals may not feel ill, they can infect others by person-to-person contact or contaminate food or water.

Some individuals may present with abnormally high temperatures, nausea, vomiting, abdominal pain, and bloody diarrhea, resulting in the excessive loss of water from the body (dehydration) and extreme tiredness. If Balantidium coli attacks the intestinal lining, it causes inflammation and "crater-like" areas of damage (ulceration). In severe cases, the ulcers are so deep that they puncture the intestinal wall (perforation), resulting in acute inflammation of the peritoneum, the membrane that lines the abdomen. Occasionally, the ulcer may diminish lung function. Balantidium coli can also cause infections in the bone and genitourinary tract.

How Can Balantidiasis Be Diagnosed?

Balantidiasis can be diagnosed easily by laboratory testing of the stool. Immature Balantidium coli parasites are usually recoverable from the stool. It is the most straightforward form of diagnosis as the parasites are large and actively motile. A more complex and invasive diagnostic method involves scraping the ulcer and examining the tissue.

Sigmoidoscopy is done to detect the damage to the colon wall by Balantidium coli. This is used to examine the colon and then extract a small tissue section for examination (biopsy). Infection of the lungs is detected with phase-contrast microscopy, which allows the study of living cells (unstained) under a microscope. Balantidiasis should be included in the differential diagnosis in cases of persistent diarrhea of patients with travel history.

What Is the Treatment?

Medical treatment of balantidiasis is administered to both symptomatic and asymptomatic patients. Symptomatic patients of balantidiasis are treated because untreated balantidiasis can become chronic and fatal. Asymptomatic patients are treated to prevent them from spreading the infection to others.

The antibiotic drug most commonly used to treat balantidiasis is Tetracycline. Tetracycline is the antibiotic of choice, but it is not recommended for pregnant women and children under eight. When Tetracycline cannot be given, drugs like Iodoquinol or Metronidazole are given. It is not necessary to isolate a person with balantidiasis. The feces (stool) of infected individuals must be disposed of and should be taken care that they do not come into contact with drinking water or food supplies. Metronidazole is administered for five days, and Tetracycline dosage is for ten days, whereas Iodoquinol is given for twenty days. The other drugs that are used are Doxycycline and Ampicillin.

What Are the Complications Associated With Balantidiasis?

  • Intestinal perforation and peritonitis are the leading causes of death in balantidiasis cases.

  • Rare complications include intestinal perforation and the spread of the parasite to the liver and mesenteric lymph nodes.

  • Pulmonary involvement, although uncommon, is more prevalent in patients with underlying conditions such as diabetes, cancer, or impaired lymphocyte function.

How Can Balantidium Coli Infection Be Prevented?

Balantidium coli infection is prevented by maintaining good hygiene. Prevention requires effective personal and community hygiene. Washing the hands with soap and water after using the toilet, changing diapers, and handling food can prevent the infection. Even if they have removable skin, washing all fruits and vegetables with water before preparing or eating them can prevent disease. Careful disposal of human feces can prevent transmission of disease.


Balantidiasis is an infection caused by the parasite Balantidium coli and mainly occurs in areas with poor hygiene. Luckily, the disease responds well to antimicrobial therapy. The prognosis for most patients with balantidiasis infection is good. Efforts to improve hygiene may lead to a reduction in the prevalence of the disease. But this disease will be present as long there are pigs in this world.

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Dr. Kaushal Bhavsar
Dr. Kaushal Bhavsar

Pulmonology (Asthma Doctors)


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