High prevalence of dientamoebiasis in patients attending a tertiary-care hospital in Northern Italy: a 6-year study

Objectives: Dientamoeba fragilis still remains neglected as a cause of intestinal complaints probably due to the misconceptions that it is uncommon and non-pathogenic. The aim of this study, partly retrospective and partly prospective, was to determine the proportion of D. fragilis infection among the infections by other intestinal parasites, in order to obtain a picture of the epidemiological situation in a population of patients suspected of having an intestinal parasitosis. Methods: Conventional diagnosis of intestinal parasitoses (microscopic examination of fresh/concentrated faeces and cultivation in Robinson’s medium) was performed on 1143 faecal samples belonging to 651 patients in a period of five years and ten months. The DNA extracted from the same samples was used in a real-time PCR assay targeting the 5.8S rRNA gene of D. fragilis. Results: Real-time PCR revealed the presence of D. fragilis in 255 samples of 162 patients. In 61 of these cases the dientamoebiasis was diagnosed by PCR alone having conventional methods detected D.fragilis in 101 patients. D. fragilis infection was detected in 24.9% of the patients, second in frequency among the diagnosed intestinal parasitoses (among protozoa infections, before Giardia intestinalis and after Blastocystis hominis). Conclusion: Though a number of studies from many parts of the world have reported patients infected by D. fragilis whose gastrointestinal symptoms solved only after therapeutic intervention, few laboratories routinely test for D. fragilis and few prevalence data, probably underestimated, are available, also due to the difficulties in detecting the parasite by conventional parasitological techniques. In this study the proportion of D. fragilis infected patients evidenced a remarkably high prevalence of dientamoebiasis in the analysed population (both Italian and foreigners). All the patients with D. fragilis infection presented with gastrointestinal symptoms and most of them were co-infected with either non-pathogenic protozoa (like Entamoeba coli and Entamoeba dispar) or protozoa whose pathogenicity is controversial (B. hominis), or harboured no protozoa other than D. fragilis or no other enteropathogenic agents (bacteria, viruses). A targeted therapy administered to most of the patients with dientamoebiasis solved gastrointestinal complaints, strengthening the accumulating evidence for the pathogenicity of D. fragilis being it the possible source of symptoms in such patients.