Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at September 1, 2016

Balantidiasis is also known as Balantidium coli infection. Balantidium coli is a type of parasite that can be transmitted from ingesting contaminated water and contaminated food. Among those who live in developed countries, it is most commonly acquired by travelers to countries with poor sanitation infrastructure.


Definition & Facts

Balantidiasis is a type of parasitic infection. It primarily affects the intestines of the organism it inhabits. While most people who are infected by this protozoan parasite may be asymptomatic (having no symptoms) or have only slight symptoms, those cases that are severe can cause serious damage to the intestines and lungs which it can spread to in rare cases.

To date, the areas where the most cases of balantidiasis have been reported include Brazil, Iran and Papua New Guinea. Balantidiasis is a type of protozoan infection, and is the physically largest type of protozoan that is known to infect humans.

Symptoms & Complaints

While most people with this condition are asymptomatic, the most commonly reported symptoms in cases of balantidiasis include the following:

Individuals who are already have a weakened immune system due to other health conditions generally report the most severe symptoms from having balantidiasis.

While most cases of balantidiasis are mild, an infection can prove fatal if it comes on suddenly and causes internal bleeding. It may also be deadly if the protozan invades the respiratory system and pneumonia develops as a result. Again, the risk of lethal complications is higher if an individual is suffering from other health problems like cancer.


Transmission primarily occurs through drinking fecal-contaminated water or eating unwashed produce or meats. Transmission can also occur through food preparation or handling infected livestock (especially pigs). Balantidiasis is thus a foodborne illness and waterborne disease.

To date, males and females are affected in equal numbers by balantidiasis. To date, worldwide reported cases are estimated to affect less than one percent of the population. The protozoan lives in pigs and thus tends to affect those who work with pigs more than other populations. The incubation period may be a few days to a few weeks; a person who is not symptomatic may still pass the infection.

The parasite has two phases: the trophozoite phase and the cyst phase. The trophozoite phase involves the parasite living in the large intestine and reproducing. The cyst phase involves the parasite producing a cyst around itself while living in the rectum. The parasite's cysts are what is typically found in an infected person's feces. Ingesting the cyst is how a person typically gets infected.

Diagnosis & Tests

Diagnosing balantidiasis first involves taking a thorough personal medical history that includes a history of recent travels. The doctor will also ask for a full list of symptoms and do a physical examination.

From there, diagnosis can usually be accomplished by testing the stool of the individual to determine the presence of a cyst. If the parasite in its cyst form is detected (usually it is possible to view it in the stool sample under a microscope), this can be used to make a definitive diagnosis. 

If the stool test results are inconclusive, there is another way to make an accurate diagnosis called a sigmoidoscopy. This diagnostic method requires the insertion of an endoscope into the intestinal area to inspect any ulcers or damage to the end of the colon. The doctor can then scrape a cell sample or biopsy off of any ulcers. These cells can then be analyzed under a microscope to confirm balantidiasis. One final diagnostic test that can be done is to test mucus from the lungs to identify the presence of the parasites.

Because contaminated water is a common source for both balantidiasis and other parasites, it is common for those with balantidiasis to also have another parasitic infection. Any additional infections must be diagnosed.

Treatment & Therapy

Although most cases of balantidiasis clear with time, treating balantidiasis is possible through the use of antibiotics. The antibiotic tetracycline is the first choice in most cases. If the individual is unable to take tetracycline or doesn't respond well, then metronidazole or iodoquinol can be prescribed.

Often rehydration and electrolyte replacement via IV drip are also prescribed to counteract the severe dehydration caused by diarrhea and/or vomiting. During the treatment phase, the individual must be extremely cautious with hygiene to avoid another infection and to avoid infecting others. 

A complication of balantidiasis infection can be appendicitis. If this occurs, surgery (an appendectomy) is done on an emergency basis to remove the appendix. Another rare complication involves the parasitic cysts spreading to the liver and lymph nodes, which will require special medical treatment. Patients that have a health history that includes autoimmune disease, diabetes mellitus, or cancer may also need special medical treatment.

Overall, treatment will continue until a stool sample lab test comes back showing no signs of the parasite. Even those who are not symptomatic should receive treatment to reduce the risk of transmission. Full recovery is likely in most cases of balantidiasis with rapid diagnosis and prompt administration of antibiotic and rehydration treatment.

Prevention & Prophylaxis

Balantidiasis is seen in countries which lack adequate sanitation infrastructure and in which pigs are handled regularly. As such, the best way to prevent balantidiasis is to take precautions when traveling to such areas.

Practicing personal hygiene such as hand washing regularly, taking great care to only eat food that is properly washed and prepared, and drinking only bottled or purified water are all preventative methods. Those who work among livestock, particularly pigs, should remain especially vigilant about hygiene.