Blastocystis infection - including symptoms, treatment and prevention

Blastocystis is a single-celled parasite which is commonly found in people who have diarrhoea or other intestinal symptoms. There is a great deal of debate about whether Blastocystis causes illness or not. Often there is another cause of the symptoms which has not yet been found.

Blastocystis infection is found throughout the world, especially in developing countries, and occurs in humans and many other types of animals.

How Blastocystis is spread

It is not known how the infection is transmitted, but it may be through contaminated food and water.

In fact, there is not much that is known with certainty about Blastocystis and research is under way to try to understand what it is and what it does.

Signs and symptoms of Blastocystis infection

Symptoms which may be caused by Blastocystis include:

  • watery or loose bowel motions or diarrhoea
  • abdominal pain
  • itching around the anus (back passage)
  • weight loss
  • excess gas.

However many people in whom Blastocystis is found have no symptoms at all.

Diagnosis of Blastocystis infection

Diagnosis is made by microscopic examination of a faecal specimen.

Incubation period

(time between becoming infected and developing symptoms)

Unknown. Blastocystis may remain in the intestines for years.

Infectious period

(time during which an infected person can infect others)

It is not known if person-to-person spread occurs.

Treatment for Blastocystis infection

Since there is debate about whether Blastocystis causes illness or not, treatment is not usually needed and most infections will go away without any treatment.  A doctor may consider treatment in people with symptoms after other infectious or non-infectious causes have been excluded.

Prevention of Blastocystis infection

As it is not known how the infection is spread, the best advice is to maintain good personal hygiene practices, prepare food carefully and avoid drinking water that may not be clean.

Since this infection may be transmitted through contaminated food and water it is advisable to exclude people with Blastocystis from childcare, preschool, school and work until there has been no diarrhoea for at least 24 hours. If working as a food handler in a food business, the exclusion period should be until there has been no diarrhoea or vomiting for 48 hours.

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