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

Abstract

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.

Keywords: Blastocystis spp; D. fragilis; E. histolytica; G. lamblia; Israeli population; intestinal protozoa; multiplex RT-PCR; stool microscopy analysis.

Fig 1

Parasite co-infections. The graph presents the number of samples with parasite co-infections, with the species pairs indicated below the graph (N = 4,113).

Fig 2

Prevalence of protozoa infection by age (N = 21,480). The graph presents the number of samples carrying each indicated parasite species in relation to patients’ age.