Abstract
BackgroundBlastocystis is a common single-celled intestinal parasite of humans and other animals comprising at least 17 genetically distinct small subunit ribosomal RNA lineages (subtypes (STs)), nine of which have been found in humans. The geographic distribution of Blastocystis subtypes is variable, but the subtypes present in Qatar are at present unknown.MethodsStool samples were collected from randomly selected, apparently healthy subjects arriving in Qatar for the first time. Blastocystis subtypes were determined by sequencing of the small subunit rRNA gene (SSU rDNA) PCR products. Phylogenetic analyses were done using Maximum Composite Likelihood method.Results71.1 % of samples were positive for Blastocystis infection based on PCR-detection methodology compared to only 6.9 % by microscopy. Prevalence of Blastocystis did not differ between the sexes nor between age classes. However, there was a regional difference in prevalence with subjects arriving from Africa showing the highest (87.6 %), those from Western Asia intermediate (68.6 %) and from Eastern Asia the lowest prevalence (67.6 %). Genetic analysis detected only three STs. ST3 was the most common (69.3 %) and ST2 was the rarest (3.5 %), while ST1 had a prevalence of 27.2 %. ST2 showed a regional variation, being absent from the 64 Western Asian Blastocystis-positive subjects. Both ST1 and ST3 showed significant differences in prevalence between the sexes.ConclusionsThis is the first report exploring the distribution of Blastocystis subtypes in our region. We recommend that stool screening via microscopy for the presence of Blastocystis should be abandoned since it is extremely insensitive. In future, the prevalence of Blastocystis infections should be based on PCR methodology and we predict that in the years ahead diagnostic PCR will become the tool of choice. More work is needed to identify the full range of Blastocystis subtypes that circulate in our region.
Highlights
Blastocystis is a common single-celled intestinal parasite of humans and other animals comprising at least 17 genetically distinct small subunit ribosomal RNA lineages (subtypes (STs)), nine of which have been found in humans
In this paper we report on the implementation of a molecular screening assay (MSA) based on real-time PCR for the detection and subtyping of Blastocystis in samples collected from migrant workers newly arriving in Qatar, and we compare the detection rate with that achieved by conventional microscopy
Prevalence of Blastocystis based on PCR method of detection Of the 608 samples tested by PCR for the presence of Blastocystis, 432 were positive and 176 negative giving an overall prevalence of 71.1 %
Summary
Blastocystis is a common single-celled intestinal parasite of humans and other animals comprising at least 17 genetically distinct small subunit ribosomal RNA lineages (subtypes (STs)), nine of which have been found in humans. There has been a large influx of migrant workers into Doha to complete very ambitious and large-scale construction projects These workers mostly originate from states in the Middle-East, Asia and Africa, the latter two being regions where intestinal parasites are common [11, 12]. The immigration policy in Qatar applies a quota system to control the number of workers entering Qatar each year according to their country of origin. This creates a dynamic population of workers that changes from year to year and requires continuous monitoring. The same is true for housemaids, who handle the food served to families, and infants and children, who are generally more susceptible to infection than adults
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