Balantidiasis is a bacterial infection of the large intestine. It is caused by the protozoan Balantidium coli (B. coli).¹ It is a rare human infection mostly affecting populations in Brazil, New Guinea and the south of Iran.¹ The main symptom of this disease is diarrhoea, and if this is not treated it can lead to complications such as gastrointestinal perforation.² Read on to find out more information on symptoms and clinical features of Balantidiasis.

Transmission and pathogenesis

Modes of transmission

B. coli is transmitted via the faecal-oral route, which is a mode of transmission for pathogens to enter the body. B. coli is found within faecal matter, and this is taken into the mouth, for example, through food or fingers if these have come into contact with the infectious faecal matter.² The protozoan can be ingested via:

• Eating contaminated food
• Drinking contaminated water
• Oral sex that involves the anus, which may have infectious faecal particles
• Putting contaminated fingers inthe mouth, for example, when biting nails

Life cycle of B. coli

When ingested, the bacteria will stay within the large intestine, where they feed on nutrients.³ The nutrients within the large intestine allow the protozoan to live and multiply within the human body for a long period of time. From the large intestine, the B. coli can then exit the body via faeces and will exist as cysts.³ Outside of the body, B. coli can either disintegrate as it is no longer living in its optimum conditions or it may continue to survive and contaminate food and water, thus continuing the life cycle of B. coli and the transmission of the infection to other human hosts.³

Clinical features

Incubation period

Incubation period is the period of time between being exposed to an infectious disease and the development of symptoms.⁴ Even if symptoms are not being shown during this period, you can still be contagious. The incubation period for B. coli can vary depending on the health of the individual, but most cases last between 3-4 days.⁵

General symptoms

In most cases of Balantidiasis, there may not be any symptoms, and if there are symptoms present, they tend to be fairly mild.¹ However, in some cases, someone with Balantidiasis may show various symptoms ranging from mild to chronic symptoms.

Diarrhoea

Diarrhoea is usually one of the main symptoms someone with Balantidiasis may suffer from.¹ This tends to be very watery and can occur frequently, and as a result, leads to further problems such as severe dehydration due to the extreme loss of body fluids. In some cases, someone with Balantidiasis may find that there is blood in their diarrhoea too, known as dysentery.^2,6 As well as blood, mucus may be found in the stool too. 

Abdominal pain

Someone with Balantidiasis may suffer from lower abdominal pain, which can range from mild to acute pain.⁶ Acute pain is usually accompanied by bloody diarrhoea and could be a sign that the colon has been perforated, leading to further health complications.^2,6

Other symptoms

Other symptoms of Balantidiasis include:

• Weight loss¹
• Nausea and vomiting¹
• Fever¹

Severe and complicated cases

If these symptoms remain untreated, it can lead to complications such as:

• Perforation of the colon
• Secondary bacterial infections
• Infections outside of the large intestine, such as pulmonary inflammation and peritonitis, are, however, rare⁶

Diagnosis

If the individual has these symptoms and a medical professional suspects them of being infected, they will ask for stool samples to test whether an individual is suffering from Balantidiasis.² This stool sample would be examined within a laboratory. The exam will involve looking for traces of B. coli within the stool using a microscope, and if this is present, it can be said that the individual has been infected by the protozoan and has Balantidiasis. As B. coli may not always survive outside of the large intestine, more stool samples may be required and will be examined as soon as possible.⁸

In rarer cases, an endoscopy may be performed.⁷ This is used to identify ulcers, which may be caused by the infection, and a sample can be scraped from the ulcer to look for traces of B. coli.⁷ Due to its invasive nature and the complexity of this procedure, this is less commonly used to diagnose someone with Balantidiasis.¹

Treatment and management

Antimicrobial therapy

If found to have Balantidiasis, antibiotics would be given, such as Tetracycline.² If an individual is unable to take this medication, Metronidazole and Iodoquinol may be prescribed instead.² Tetracycline is usually given at a dosage of 500 mg, four times a day, and is to be administered over the course of 10 days.⁹ Due to an increase in antimicrobial resistance, these antibiotics must be taken as advised, even if the individual is no longer showing symptoms during their time of taking the antibiotics.

Supportive care

Hydration and electrolyte management

If the individual with Balantidiasis suffered from severe diarrhoea and vomiting, it is likely that they may have lost water from the body and become severely dehydrated.¹ In such cases, an individual may undergo fluid replacement via an IV drip to restore lost fluids, as well as restore any lost electrolytes.⁹ The individual may also be advised to have a starch-free diet.⁹

Management of complications

Surgery may be required in cases where the infection has affected other parts of the body outside of the large intestine.⁹ One example of this would be an appendectomy to treat acute appendicitis as a result of Balantidiasis. An individual may have to be monitored in the long term by having regular follow-up appointments to ensure the individual is recovering as expected from Balantidiasis and any other associated conditions.⁹

Prevention and control

Practising good hygiene will prevent the spread of B. coli. This would include:

• Washing hands thoroughly with warm water and soap after using the toilet and before food is handled²
• Practising safe sex, especially if performing oral sex
• Washing fruit and vegetables during food preparation and before eating it 
• Having access to safe, clean water that is suitable for drinking⁹

If infected with B. coli, it is not necessary to quarantine; however, it is advised to dispose of faeces correctly to avoid transmission to other people.

FAQs

What is the main clinical symptom of balantidiasis?

Someone with Balantidiasis is usually asymptomatic but may sometimes show symptoms, with the main symptom being diarrhoea, which in some cases can be bloody.¹

What are the features of balantidium coli (B. coli)?

They can appear in different ways depending on what stage of the life cycle they are in. B. coli can be visualised as a spore when found outside of the large intestine, for example, if found within faeces. The protozoan can also be presented as trophozoites when within the large intestine, and it is at this stage that they are activated, grow and multiply.¹⁰ These trophozoites tend to be large and are found to have cilia on their surface.⁸ Both cysts and trophozoites can be identified during examinations, which will lead to the diagnosis of Balantidiasis.²

What are the risk factors for balantidiasis?

As B. coli can also be found in the faeces of animals, there is an increased risk of being infected if handling fertiliser that has been contaminated by animal faeces.⁹ The risk of being infected is also increased if living areas lack access to clean, safe water. Dirty water that has been in contact with sewage, for example, may be contaminated with B. coli. If infected with B. coli, the risk of having more severe symptoms and developing further infections is increased if an individual already has pre-existing health conditions, such as diabetes.

Summary

Balantidiasis is a rare infection of the large intestine caused by the protozoan Balantidium coli. Someone infected usually does not show any symptoms, but in some cases may show symptoms, such as diarrhoea (which can be bloody), high fever, and abdominal pain. These symptoms can lead to further complications within the body. Treatment of Balantidiasis involves taking a course of antibiotics. The disease can be prevented by practising good hygiene, such as washing hands properly.