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SakariJokiranta
AnuKantele

Dientamoebiasis in Adults

See also article Dientamoebiasis in children Dientamoebiasis in Children.

Causative agent

  • The protozoan Dientamoeba fragilis which, despite its name, belongs to flagellate protozoans and not amoebas

Distribution

  • Possibly worldwide
  • In industrialised countries, some infections are encountered in tourists returning from tropical or subtropical regions but also endemic infections are common.
  • Prevalence varies greatly depending on the country, region and age group. The highest prevalence rates have been reported in Denmark.

Transmission

  • According to current understanding the infection is transmitted from person to person through food or drink that is contaminated by faeces, or directly. Also pinworms may transmit this protozoan. An infectious cyst stage of the parasite which makes transmission easier has been discovered.
  • Also asymptomatic persons may transmit the disease.

Significance

  • Dientamoeba causes symptoms only to a proportion of individuals. The protozoan should be searched and treated only in those with symptoms.
  • Cases are most common in children in day care age and in their parents (transmission within the family). According to Finnish data, samples are positive for Dientamoeba in less than 15% of adults. Country-specific variation may exist.
  • The disease is not life-threatening even in its most severe forms, but prolonged symptoms may significantly interfere with the patient's daily life.

Signs and symptoms

  • Some of those infected remain asymptomatic. Asymptomatic carrier state may be particularly common in children (see Dientamoebiasis in Children). There may be both symptomatic and asymptomatic persons with infection within the same family.
  • At the time of diagnosis, the symptoms have often prevailed for months or even years in those with symptoms.
  • The symptoms vary from mild flatulence to a troublesome clinical picture that restricts and hampers the patient's life and well-being in many ways.
  • In addition to flatulence and prolonged diarrhoea or loose stools, symptoms may include bathroom urgency, intermittent constipation, abdominal pain and cramps, weight loss and tiredness.

Diagnosis

  • The primary test is detection of nucleic acids of intestinal parasites. A single sample is probably sufficient.
    • In some laboratories, testing for Dientamoeba fragilis must be separately requested.
  • The secondary test is amoeba staining, using samples collected on three different days.
  • The results of basic laboratory tests are usually not abnormal; in a small share of patients, oesinophilia is present and even slight elevation of liver enzymes, which become normal when dientamebiasis is treated.

Treatment and prognosis

  • It is not necessary to treat asymptomatic carriers. Treating an asymptomatic person may be considered if a family member has recurrent symptomatic Dientamoeba infections and recurrent reinfections are suspected.
  • Metronidazole is the drug of choice in outpatient care (400-750 mg 3 times daily for 10 days).
  • If eradication is not successful with metronidazole, the following may be used in the treatment (under special license): paromomycin, secnidazole or tinidazole. Secnidazole and tinidazole belong, together with metronidazole, to the same group of drugs, the nitroimidazoles; they are less effective than paromomycin. These alternative drugs are favoured e.g. in specialized care. The effect of doxycycline has proven to be so weak that it is no longer used.
  • The success of the treatment is controlled by a nucleic acid detection test 4 weeks after completing the treatment.
  • If a microbiologically successful treatment does not have an effect on the symptoms, the aetiology of the symptoms should be sought elsewhere. If the symptoms are relieved and later return, a reinfection should be suspected.

References

  • Stark D, Barratt J, Roberts T et al. A review of the clinical presentation of dientamoebiasis. Am J Trop Med Hyg 2010;82(4):614-9. [PubMed]
  • Nagata N, Marriott D, Harkness J ym. Current treatment options for Dientamoeba fragilis infections. Int J Parasitol Drugs Drug Resist 2012;2():204-15. [PubMed]
  • van Lieshout L, Roestenberg M. Clinical consequences of new diagnostic tools for intestinal parasites. Clin Microbiol Infect 2015;21(6):520-8. [PubMed]
  • Pietilä JP, Meri T, Siikamäki H ym. Dientamoeba fragilis - the most common intestinal protozoan in the Helsinki Metropolitan Area, Finland, 2007 to 2017. Euro Surveill 2019;24(29)[PubMed].