Dientamoeba fragilis – the most common intestinal protozoan in the Helsinki Metropolitan Area, Finland, 2007 to 2017

Abstract

Background Despite the global distribution of the intestinal protozoan Dientamoeba fragilis, its clinical picture remains unclear. This results from underdiagnosis: microscopic screening methods either lack sensitivity (wet preparation) or fail to reveal Dientamoeba (formalin-fixed sample). Aim In a retrospective study setting, we characterised the clinical picture of dientamoebiasis and compared it with giardiasis. In addition, we evaluated an improved approach to formalin-fixed samples for suitability in Dientamoeba diagnostics. Methods This study comprised four parts: (i) a descriptive part scrutinising rates of Dientamoeba findings; (ii) a methodological part analysing an approach to detect Dientamoeba -like structures in formalin samples; (iii) a clinical part comparing demographics and symptoms between patients with dientamoebiasis (n = 352) and giardiasis (n = 272), and (iv) a therapeutic part (n = 89 patients) investigating correlation between faecal eradication and clinical improvement. Results The rate of Dientamoeba findings increased 20-fold after introducing criteria for Dientamoeba -like structures in formalin-fixed samples (88.9% sensitivity and 83.3% specificity). A further increase was seen after implementing faecal PCR. Compared with patients with giardiasis, the symptoms in the Dientamoeba group lasted longer and more often included abdominal pain, cramping, faecal urgency and loose rather than watery stools. Resolved symptoms correlated with successful faecal eradication (p < 0.001). Conclusions Previously underdiagnosed, Dientamoeba has become the most frequently recorded pathogenic enteroparasite in Finland. This presumably results from improved diagnostics with either PCR or detection of Dientamoeba -like structures in formalin-fixed samples, an approach applicable also in resource-poor settings. Symptoms of dientamoebiasis differ slightly from those of giardiasis; patients with distressing symptoms require treatment.

Dientamoeba fragilis Infection in Patients with Digestive and Non-Digestive Symptoms: A Case-Control Study

“…was only 1 case. Dientamoeba/Giardia mixed infection was documented 7.1% from 1 population [33] and 9% from another [22] in disagreement with our study. Enteropathogens/D.…”

“…Wakid has identified the infection in food processing workers based on microscopic examination of permanently stain fecal smears. Microscopy was thought to be a less effective detection method for D. fragilis and often underestimated the frequency of the parasite, compared to the molecular diagnostic methods [20][21][22]. According to a recent study, there was an annual increase of 28% in the detection of D. fragilis infection after implementation of a fecal PCR in diagnosis.…”

“…Enteropathogens/D. fragilis coinfection was registered in 58% of a study population [35] and in 23% of another [22]. It is worth mentioning that the Blastocystis sp.…”

Optimization of routine microscopic and molecular detection of parasitic protozoa in SAF-fixed faecal samples in Sweden

“…The pathogenic role of D. fragilis has been debated [16][17][18]21,51,52] and the need for screening is questioned. A recent study from Finland also shows that wet mount screening was useful for D. fragilis detection [20].…”

“…Dientamoeba fragilis is common, but confirmation of virulence and the potential mechanisms of pathogenicity are yet to be determined [16][17][18][19][20]. Reported prevalence figures vary depending on methods used, patient population and location [20][21][22][23]. Trophozoites of G. intestinalis and E. histolytica are analysed either as motile in fresh samples or by staining of SAF-fixed samples, mainly only on request.…”