Dientamoeba fragilis infection - including symptoms, treatment and prevention

Dientamoeba fragilis (D. fragilis) is a single-celled parasite. It is not known for certain whether D. fragilis causes illness or not. D. fragilis is commonly found in faeces, both of people who are well and in people who have diarrhoea or other intestinal symptoms.

How Dientamoeba fragilis is spread

Uncertain. There are two main theories of how D. fragilis spreads.

D. fragilis may be spread through contamination of hands, objects or food with infected faeces. The parasite is then taken in by the mouth. 

Alternatively, D. fragilis may be spread by threadworms (pinworms). D. fragilis might be protected by threadworm eggs. Threadworms are caught when someone swallows the worm’s eggs. Threadworm eggs hatch inside the bowel, where they live, then travel out through the anus (back passage) to lay their eggs on the skin there at night time. Threadworm eggs may be picked up on the fingers and transferred to the mouth if the person scratches their bottom or does not wash their hands after going to the toilet. Threadworm eggs may also fall off into bedding or clothing, or be wafted into the air, settling on many surfaces in the home or school.

Signs and symptoms of Dientamoeba fragilis infection

People who are infected with D. fragilis may not have any symptoms.

Symptoms, when they occur, may include: abdominal pain, diarrhoea, excess gas, poor appetite, fatigue, nausea, weight loss, vomiting and tiredness. It may be that these symptoms are not caused by D. fragilis infection.

Diagnosis of Dientamoeba fragilis infection

Exclude other causes of illness.

Diagnosis is made by examination or PCR testing of a faecal specimen.

Incubation period

(time between becoming infected and developing symptoms)


Infectious period

(time during which an infected person can infect others)


Treatment for Dientamoeba fragilis infection

Most people with D. fragilis infection do not require treatment.

Retesting of a faecal specimen after antimicrobial treatment (if given) is not recommended.

Seek medical advice if any of the following symptoms are present (note that these are unlikely to be caused by D. fragilis):


  • signs of dehydration, such as thirst and decreased urination, lethargy, dry mouth, feeling faint on standing
  • fever
  • severe abdominal pain
  • bloody diarrhoea.


  • signs of dehydration, such as thirst and decreased urination, lethargy, dry mouth, sunken eyes, feeling faint on standing
  • fever
  • abdominal pain
  • bloody diarrhoea
  • any symptoms in a child less than 12 months of age.

Prevention of Dientamoeba fragilis infection

  • People with confirmed D. fragilis without symptoms do not need to be excluded.
  • Exclude people with diarrhoea 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.
  • Infants, children and adults with diarrhoea should not swim until there has been no diarrhoea for 24 hours.
  • Follow good hand washing and keeping areas clean procedures.