Dientamoebiasis

Dientamoebiasis is a medical condition caused by infection with Dientamoeba fragilis. Dientamoeba fragilis is a single celled parasite that infects the lower gastrointestinal tract of humans.

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Symptoms

The most commonly reported symptoms in conjunction with infection with Dientamoeba fragilis include abdominal pain (69%) and diarrhea (61%). ^[1] Diarrhea may be intermittent and may not be present in all cases. The degree of symptoms may vary from asymptomatic to severe ^[2], and can include weight loss, vomiting, fever, and involvement of other digestive organs. A study from Sydney Australia of 60 individuals who were found to be infected with Dientamoeba fragilis found that all had symptoms.^[3] Researchers have reported that symptoms may be more severe in children. Additional symptoms reported have included: ^[4]

1. Weight loss
2. Fatigue
3. Nausea and vomiting
4. Fever
5. Uritcaria (skin rash)
6. Pruritis (itchiness)
7. Biliary infection

Transmission

Parasites similar to Dientamoeba fragilis are transmitted by consuming water or food contaminated with feces. Organisms similar to Dientamoeba fragilis are known to produce a cyst stage which is able to survive outside of the host and facilitate infection of new hosts. However, the exact manner in which Dientamoeba fragilis is transmitted is not yet known, as scientists have reported that the organism is unable to survive outside its human host for more than a few hours after excretion, and no cyst stage has been found. ^[5]

Early theories of transmission suggested that Dientamoeba fragilis was unable to produce a cyst stage in infected humans, but some animal existed that in which it did produce a cyst stage, and this animal was responsible for spreading it. However, no such animal has ever been discovered. ^[4] A later theory suggested the organism was transmitted by pinworms, which provided protection for the parasite outside of the host. However recent study has failed to show any association between Dientamoeba fragilis infection and pinworm infection. ^[5]

Diagnosis

Diagnosis is usually performed by submitting a stool sample for examination by a parasitologist in a procedure known as an Ova and Parasite (O&P) Examination.

The failure of routine O&P examination to identify Dientamoeba fragilis infection has been noted:

1. One researcher investigated the phenomenon of symptomatic relapse following treatment of infection with Dientamoeba fragilis in association with its apparent disappearance from stool samples. The study found that the organism could still be detected in patients through colonoscopy or by examining stool samples taken in conjunction with a saline laxative. ^[6]
2. A study found that trichrome staining, a traditional method for identification, had a sensitivity of 36% (9/25) when compared to stool culture. ^[7]
3. An additional study found that the sensitivity of staining was 50% (2/4), and that the organism could be successfully cultured in stool specimens up to 12-hours old which were kept at room temperature. ^[8]

Medical acceptance and misdiagnosis

Researchers have noted that physicians in many countries have been slow to address infection with Dientamoeba fragilis, despite the body of clinical literature that links it with symptoms. ^[4] Early microbiologists reported that the organism was not pathogenic, even though six of the seven individuals from whom they isolated it were experiencing symptoms of dysentary. Their report, published in 1918, concluded the organism was not pathogenic because it consumed bacteria in culture, but did not appear to engulf red blood cells was seen in the most well known disease causing amoeba of the time, Entamoeba histolytica. This initial report may still be contributing to the reluctance of physicians to diagnose the infection. ^[4]

An Australian study identified a large number of patients considered to have Irritable bowel syndrome who were actually infected with Dientamoeba fragilis. ^[9] Symptoms resolved following treatment.

Genetic diversity

A study of Dientamoeba fragilis isolates from 60 individuals with symptomatic infection in Sydney Australia found that all were infected with the same genotype. ^[3]

Prevalence

Although Dientamoeba fragilis has been described as an infection that is "emerging from obscurity," ^[4]it has become one of the most prevalent gastrointestinal infections in industrialized countries, especially among children and young adults. A Canadian study reported a prevalence of approximately 10% in boys and girls aged 11-15 years, ^[5], a prevalence of 11.5% in individuals aged 16-20, and over 20 had a lower incidence of 0.3%-1.9%.

Treatment

Successful treatment of the infection with Iodoquinol, Doxycycline, Metronidazole, Paromomycin, and Secnidazole have been reported. ^{[4] [2]}

References