The effectiveness of empirical anti-parasitic treatment in returning travellers with persistent abdominal symptoms

The epidemiology of intestinal protozoa in the Israeli population based on molecular stool test: a nationwide study

Stool examination using microscopy was the traditional method for the diagnosis of intestinal parasites. Recently, the use of molecular tests to identify stool protozoa has become the main tool used in most clinical laboratories in Israel. This study aimed to evaluate the prevalence of intestinal parasites in Israel and to compare this prevalence in laboratories that use molecular tests vs a laboratory that uses microscopy. Samples collected from January to October 2021 at seven laboratories were analyzed by real-time PCR (RT-PCR) or by microscopy. The multiplex panel included the following pathogens: Giardia lamblia, Entamoeba histolytica, Cryptosporidium spp., Cyclospora, Dientamoeba fragilis, and Blastocystis spp. Overall, 138,415 stool samples were tested by RT-PCR and 6,444 by microscopy. At least one protozoa species was identified in 28.4% of the PCR-tested samples compared to 4.6% of the microscopy-tested samples. D. fragilis was the most common PCR-identified species (29%). D. fragilis, G. lamblia, and Cryptosporidium spp. were mainly found in pediatric population, while Blastocystis spp. was most prevalent among adults (P < 0.001). In a sub-cohort of 21,480 samples, co-infection was found in 4,113 (19.15%) samples, with Blastocystis spp. and D. fragilis being the most common (14.9%) pair. Molecular stool testing proved more sensitive compared to microscopy. D. fragilis was the most commonly detected pathogen. The above profile was identified during the COVID pandemic when traveling was highly restricted and most likely represents the locally circulating protozoa.

IMPORTANCE

This study sheds light on the prevalence of stool parasites in Israel. Additionally, this study indicates that the shift from microscope analysis to molecular tests improved protozoa diagnosis.

The clinical significance of Dientamoeba fragilis and Blastocystis in human stool-retrospective cohort study

OBJECTIVES

The aim of this study was to assess the clinical significance of Dientamoeba fragilis (DF) and Blastocystis species (Bs) in human stool.

METHODS

Observational study of patients ≥18 years, who were tested by stool multiplex PCR for bacteria and parasites between April 2019 and March 2022. Although DF and Bs are part of the PCR kit, these results are not routinely reported to the patient or the ordering physician. The main outcomes were the incidence of symptoms during 14 days before the referral to stool PCR test, and the incidence of several clinical outcomes during 60 days after the PCR test (symptoms, referrals to further evaluation, prescription of symptomatic, or antibiotic treatment).

RESULTS

A total of 27 918 patients were tested by stool PCR during the 3 study years. A total of 6215 (22.3%) and 5337 (19.2%) were positive for DF and Bs, respectively. The incidence of symptoms before the test was similar in those positive for Bs or DF and those with all-negative PCR (adjusted OR and 95% CI of 0.87 [0.80-0.95] and 0.82 [0.76-0.88] for Bs and DF, respectively), whereas significantly higher (2.47 [2.23-2.73]) in those positive for the other multiplex PCR assay components. During the 60 days after the test, the prevalence of any of the outcomes was similar in those positive for Bs or DF and those with negative PCR (adjusted OR and 95% CI of 0.92 [0.83-1.02] and 0.89 [0.81-0.97] for symptoms, 0.84 [0.75-0.94] and 0.93 [0.85-1.01] for referrals, 0.88 [0.75-1.03] and 0.82 [0.71-0.94] for symptomatic treatment, and 0.88 [0.75-1.02] and 0.86 [0.75-0.98] for antibiotic treatment in the Bs and DF positive individuals, respectively). The PCR cycle threshold was not associated with any of the outcomes.

DISCUSSION

Positive stool PCR for DF or Bs was not associated with any of the measured clinical outcomes.

Should we treat Blastocystis sp.? A double-blind placebo-controlled randomized pilot trial

BACKGROUND

Blastocystis sp. is a worldwide-distributed protist colonizing the guts of humans and a great variety of animals. It is unclear whether it is just a commensal or an infectious parasite that prompts eradication.The main objective of this study was to evaluate the usefulness of metronidazole in patients with gastrointestinal symptoms harbouring only Blastocystis sp. In addition, we explored whether Blastocystis subtype or concomitant parasitic infection detected by polymerase chain reaction (PCR) may influence treatment outcome.

METHODS

We included adults with persistent gastrointestinal symptoms (>14 days) visiting a primary care physician and in whom stool microscopy revealed only Blastocystis sp. Eligible patients were randomized to receive 10 days of metronidazole or placebo, followed by a crossover if still symptomatic. The primary outcome was normal stool consistency. Secondary outcomes were the changes in other abdominal symptoms (bloating, flatulence, abdominal pain, number of daily bowel movements) and general wellbeing. After the clinical phase of the study, Blastocystis subtypes were determined by PCR sequencing and stool samples were tested for 11 other protozoa with an in-house PCR.

RESULTS

We screened 581 outpatients for inclusion, of which 50 met the eligibility criteria. There was no difference in the primary outcome, nor any of the secondary outcomes between the subjects treated with metronidazole and placebo.The most frequent Blastocystis subtypes were ST4 (11/36) and ST2 (10/36). The in-house PCR was positive for other protozoa in 25% (10/40) of the patients. We identified Dientamoeba fragilis in 5, Entamoeba dispar in 3 and Cyclospora cayetanensis in 2 patients. Stratified analysis according to Blastocystis subtype or the presence of other protozoa showed no significant difference in treatment outcome with metronidazole or placebo.

CONCLUSIONS

Among patients infected with Blastocystis sp., metronidazole, compared with placebo, was not better in improving gastrointestinal symptoms, irrespective of subtype or microscopically undetected coinfection with other protozoa.

Persistent abdominal symptoms in returning travellers: clinical and molecular findings

BACKGROUND

Persistent abdominal symptoms (PAS) are the leading cause of post-travel morbidity although there is a paucity of evidence concerning the aetiology of this condition. Recently molecular methods for protozoa detection in stool have been introduced. Herein, we describe the clinical aspects and the prevalence of gastrointestinal protozoa in returning travellers with PAS.

METHODS

From 2017 to 2019, clinical information and stool specimens from returning travellers with PAS were analysed for the presence of parasites using the Allplex-GI-Parasite-assay. Stool findings from symptomatic patients without a travel history were used as a comparator.

RESULTS

During the 2-year study, 203 stool specimens from returning travellers were analysed. The median duration of symptoms before seeking care was 6 months, the most common symptoms were fatigue (79.2%), abdominal pain (75.7%) and loose stool (70.8%).Most of travellers had returned from Asia (57.6%), mainly from the Indian-subcontinent and only 52.6% were backpackers. Altogether, 36.9% samples were positive for protozoa, with Blastocystis hominis being the most common (26.6%) in samples, followed by Dientamoeba fragilis (18.7%), Giardia lamblia (3.0%) and Cryptosporidium spp (0.5%). The former two were dominant in all regions. In all cases but one, G. lamblia was acquired, but one were acquired in the Indian subcontinent (odds ratios 16.9; 95% confidence intervals: 1.9-148.3). Entamoeba histolytica was not detected. The demographic characterization of the 1359 non-travellers was comparable with the travellers. Among them D. fragilis was the most common followed by B. hominis, which was significantly less frequent compared among the travellers (16.7% vs 26.6%, P < 0.001). Average Cycle threshold values for each stool parasites were comparable between the two groups.

CONCLUSION

Among returning travellers with PAS, more than one-third were positive for gastrointestinal protozoa. A low rate of giardia was found and no E. histolytica while B. hominis followed by D. fragilis were the dominant findings. Further studies are required to better understand the role of these protozoa in PAS.

Persistent abdominal symptoms: a persistently neglected topic in travel medicine

Persistent abdominal symptoms are a common complaint in returning travellers; yet, there is very sparse evidence to support the causes and potential aetiologies. New molecular stool-testing techniques and accurate clinical studies may shed light on this gap in our knowledge, paving ways for more successful management of this common and difficult problem.

Giardia lamblia miRNAs as a new diagnostic tool for human giardiasis

Background

Giardia lamblia is a very common cause of gastrointestinal symptoms worldwide. There are several methods for the diagnosis of Giardia infection, however none are ideal. We aim to find a new, microRNA-based method that will improve the currently available diagnostic methods for giardiasis.

Methods

Deep-sequence profiling of Giardia small-RNA revealed that miR5 and miR6 are highly expressed in Giardia. These miRNAs were tested by qRT-PCR in duodenal biopsies of patients with giardiasis who were positive by microscopic pathological evaluation. The gastric biopsies of the same patients served as negative control tissues. Additionally, these miRNAs were evaluated in stool samples of patients with proven giardiasis.

Results

All histologically proven duodenal biopsies of patients with Giardia infection were positive for Giardia miR5, with a mean threshold cycle (Ct) of 23.7, as well as for Giardia DNA qPCR (16S-like gene, mean Ct 26.3). Gastric biopsies which were tested as a control all were negative. Stool evaluation of miR6 in patients with giardiasis showed 90% specificity but only 66% sensitivity, and a lower accuracy rate was obtained with miR5.

Conclusion

Giardia miR5 testing in duodenal biopsies may be a new method for the diagnosis of giardiasis. It seems to be more sensitive when compared with testing for Giardia DNA by qPCR in duodenal biopsies. It will be important to investigate the contribution of routine Giardia miRNA testing in duodenal biopsies from patients with persistent abdominal symptoms

Giardiasis is a major cause of diarrheal disease throughout the world. It is more common in areas with poor sanitation such as in many low-income countries, but it occurs in high-income countries as well. It is the most commonly identified intestinal parasite in the United States and it is endemic in other industrialized countries. The causative agent is the flagellate protozoan Giardia lamblia, and transmission is mainly by the fecal-oral route. The basic method of diagnosis is stool examination. It is usually found through stool microscopy examination which should be performed on fresh stool and repeated in 3 days. Despite some newer diagnostic methods, Giardia is still difficult to detect, often leading to misdiagnoses.

In this study we show that using Giardia microRNA (miR5) as a marker for Giardia infection in duodenal biopsies may be a new method for diagnosis of giardiasis. It appears to be more sensitive than histological diagnosis and also more sensitive than Giardia DNA testing in duodenal biopsies. Interestingly, in our patients, duodenal biopsies were done for persistent abdominal symptoms and the finding of Giardia in their biopsy was unexpected. Thus, testing duodenal biopsies for Giardia miRNA in patients with persistent abdominal symptoms might contribute to diagnosis and prompt treatment for those with giardiasis.