Epidemiological and clinical characteristics of Dientamoeba fragilis infection

Dientamoeba fragilis: An emerging pathogen

Dientamoeba fragilis is a protozoan of the gastrointestinal tract, very prevalent in our environment and responsible for diverse clinical symptoms mainly abdominal pain, diarrhoea and eosinophilia, although some infected patients are asymptomatic. Since the first description just a century ago, there are many unanswered questions: its different morphologies and the role of each of them, its actual prevalence, the mode of transmission, its pathogenicity, or the treatment of choice, continue to be source of controversy. Risk factors associated with infection by D. fragilis are: contact with children, residence in a rural area, and co-infection by Enterobius vermicularis. New molecular diagnostic techniques in the form of commercial multi-diagnostic panels are now considered first choice techniques. Paromomycin show higher cure rates, than metronidazole.

First detection and molecular characterization of Dientamoeba fragilis in cattle

Dientamoeba fragilis is a flagellated protozoan with amoeba-like morphology that inhabits the human gastrointestinal tract. It is endemic in a vast geography around the world, including developed countries. There are limited studies on non-human hosts of the parasite, and suitable hosts have not been clarified. The parasite has been detected in non-human primates, pigs, cats, dogs and rats. There is no study in the literature investigating and detecting the presence of this parasite in cattle. In this study, stool samples taken from 163 different cattle and calves from 11 different farms between March 2017 and May 2022 were examined for the detection of D. fragilis via PCR. Trichrome staining was performed on all PCR-positive samples. The isolates with the expected amplicon size were sequenced using the 18S ribosomal RNA region, and their genotypes were determined by BLAST analysis. Sequences were analysed with the most similar and reference sequences in the literature, forming a phylogenetic tree. We detected D. fragilis in 31 (19.01%) of the 163 stool samples. D. fragilis cysts/trophozoites were detected by trichrome staining method in six of 31 samples. All PCR products selected for molecular analysis from positive samples had the same nucleotide sequence. As a result of BLAST analysis, all sequences were determined to belong to D. fragilis genotype 1. This study determined for the first time that cattle are suitable hosts for D. fragilis. Furthermore, the parasite subtype we detected belongs to genotype 1, which is the most common type in humans, suggesting that the parasite may have a zoonotic character. Our result is important in terms of the epidemiology of the parasite, as the mode of transmission is controversial, and available data on its suitable hosts are limited.

Should Dientamoeba fragillis be looked for in pediatric digestive pathology of an unknown cause? A proposed pilot case-control study

INTRODUCTION

Dientamoeba (D.) fragilis is a common intestinal protozoan with an unresolved clinical significance. The association between D. fragilis and the etiology of gastrointestinal symptoms in children is unclear. Metronidazole is often used for treatment. The aims of this study are to clarify the clinical relevance of D. fragilis in children with gastrointestinal symptoms, and to determine the clinical and microbiological efficacy of metronidazole in D. fragilis-infected children with gastrointestinal complaints.

METHODS

A prospective case-control study was performed from October 2017 to February 2019. A total of 106 individuals aged 1-17 were included. Out of the 106; 59 showed gastrointestinal symptoms (case group), and 47 were without gastrointestinal symptoms (control group). We excluded 2 patients from the case group. D. fragilis was diagnosed by real-time PCR in stool samples. A 10-day course of oral Metronidazole was prescribed in D. fragilis positive children with GI symptoms. Clinical data before and after the treatment as well as peripheral eosinophilia in previous blood samples, were recorded.

RESULTS

Of the 104 participants, D. fragilis was found in 17 (29.8%) children from the case group, whereas in the control group the parasite was detected in 11 patients (23.4%) with an odds ratio (OR) of 1.39 (IC 95% 0.53-3.75, p=0.46). The most prevalent clinical manifestation was abdominal pain (46/57, 80.7%). Seventeen cases with a positive PCR received anti-parasitic treatment according to the established protocol, although during the collection period we received only 11 stool samples to perform the post-treatment follow-up. The PCR of the D. fragilis remained positive in 3 patients (3/11, 27.27%). Despite achieving the eradication of the parasite, 4/8 patients (50%) continued with digestive symptoms.

CONCLUSIONS

According to our study there were no differences between the D. fragilis infection in children with or without gastrointestinal symptoms. No relation was found between the clinical and microbiological responses after said D. fragilis treatment. Therefore, we conclude that it is not justified to look specifically for D fragilis in pediatric patients with abdominal symptoms.

Epidemiology and clinical features of intestinal protozoan infections detected by Real-time PCR in non-native children within an Italian tertiary care children's hospital: A cross-sectional study

BACKGROUND

Enteric parasite infections are underestimated due to the limited sensitivity and specificity of microscopy, which remains the diagnostic gold standard in routine clinical practice. This could be a major problem in high-income countries, where the burden of parasitic diseases is low. In recent years, Multiplex Real-Time polymerase chain reaction (RT-PCR) based methods have been implemented. Therefore, the aim of this study was to evaluate the prevalence of four enteric protozoan species detected by RT-PCR in non-native children in Italy, and to describe their clinical characteristics.

METHODS

Adopted and immigrant children, evaluated for migration health assessment between 2017 and 2020 in a tertiary care children's hospital in Italy, were enrolled. Molecular analysis for Giardia lamblia, Dientamoeba fragilis, Blastocystis hominis, and Entamoeba histolytica, was conducted by in-house RT-PCR.

RESULTS

Overall, 209 children were enrolled and 70% of them resulted positive by RT-PCR for at least one enteric parasite. B. hominis (47.8%) was the most commonly identified protozoa, followed by D. fragilis (44.5%). Co-infections with multiple pathogens were detected in 35.4% of the samples. Almost 80% of parasite-positive children were asymptomatic and the most common symptom was flatulence (60.7% of symptomatic children). Eosinophils were significantly increased in RT-PCR positive children compared to the negative ones and children with D. fragilis presented the highest eosinophils count.

CONCLUSIONS

The In-house Multiplex RT-PCR assay provides a valid molecular detection system for selected enteric parasites. This novel and accurate diagnostic method can help in increasing the detection rate of parasite infection, especially in high-risk population.

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

In most developing countries, Dientamoeba fragilis infection is an obscure protozoan infection. We aimed to determine a frequency and clinical importance of D. fragilis infection in Taif, Saudi Arabia. A 1-year case control study included patients with gastrointestinal (cases, n=114) or non-gastrointestinal symptoms (controls, n=90). The fecal samples were examined with the classical parasitological methods for intestinal protozoa, and by real time PCR for D. fragilis. The infection by D. fragilis was detected in 5.8% by PCR and in 4.4% patients by microscopy. The infection was identified more in control group (n=9) than in cases (n=3); a sole infection in 11 patients and mixed with Giardia in 1 patient. The other enteric parasites detected were Blastocystis sp. (8.3%), Giardia sp. (5.3%), Cryptosporidium sp. (2.9%), Entamoeba histolytica (1.4%), Entamoeba coli (0.9%) and Hymenolepis nana (0.4%). Our results tend to reinforce the need to increase awareness of D. fragilis infection in Saudi Arabia.

Dientamoeba fragilis in children: a systematic review on diagnostic considerations and efficacy of treatment

Introduction: The presence of D. fragilis in feces is characterized by an asymptomatic carrier ship to a spectrum of gastrointestinal symptoms. However, a causal relationship remains to be elucidated. In this systematic review, we aimed to evaluate the relationship between the eradication of D. fragilis and symptoms to establish the strength of evidence that D. fragilis in symptomatic children warrants antibiotic treatment.Areas covered: This systematic review covers a challenge in daily clinical practice. Is it necessary to test for D. fragilis in children with gastrointestinal symptoms and does a positive fecal PCR test warrant treatment?Expert opinion: Testing for D. fragilis seems justified in a selection of children with persistent unexplained chronic abdominal pain and diarrhea. Treatment of D. fragilis should be withhold until other causes like celiac disease have been excluded. Both microscopic and Real Time-PCR methods (or a combination of the two) can be used for diagnosis. Paromomycin or clioquinol are antibiotics of choice based on their small spectrum of activity, fewer side effects, and better eradication rates than metronidazole. Future randomized studies, with strict inclusion criteria, appropriate diagnostic testing, and doses of antibiotics based on bodyweight are warranted.

[Differential diagnosis of hypereosinophilia]

Eosinophilia is defined as an elevated absolute number of eosinophilic leukocytes in peripheral blood or tissue. Its absolute number also defines the grade of eosinophilia. The main causes are allergic (including drug side effects) and infectious triggers but malignant and autoimmune diseases can also result in eosinophilia. Severe eosinophilia with the number of eosinophils >5000/µl are mostly caused by myeloproliferative disorders, eosinophilic granulomatosis with polyangiitis or during tissue migration in parasitic tissue infections. Hypereosinophilic syndrome is defined as eosinophilia with >1500 eosinophils/µl and a duration of more than 6 months by exclusion of parasitic infections, allergies or other causes of tissue eosinophilia with end-organ damage. For the diagnosis of a persistent eosinophilia a detailed medical history and physical examination should be followed by early organ screening, infection diagnostics especially for helminth infections and hematological laboratory analyses including bone marrow investigations.