Detection, Molecular Identification and Transmission of the Intestinal Protozoa Blastocystis sp. in Guinea from a Large-Scale Epidemiological Study Conducted in the Conakry Area

Abstract

Blastocystis sp. is a single-celled parasite estimated to colonize the digestive tract of 1 to 2 billion people worldwide. Although it represents the most frequent intestinal protozoa in human stools, it remains still under-investigated in countries with a high risk of infection due to poor sanitary and hygiene conditions, such as in Africa. Therefore, the present study was carried out to determine the prevalence and subtype (ST) distribution of Blastocystis sp. in the Guinean population. For this purpose, fecal samples were collected from 500 individuals presenting or not digestive disorders in two hospitals of Conakry. Search for the parasite in stools was performed by real-time PCR targeting the small subunit rDNA gene followed by sequencing of the PCR products for subtyping of the isolates. A total of 390 participants (78.0%) was positive for Blastocystis sp. Five STs were identified in the Guinean cohort (ST1, ST2, ST3, ST4 and ST14) with varying frequency, ST3 being predominant. Among them, ST4 was found in only two patients confirming its global rarity in Africa whereas infections by ST14 were likely the result of zoonotic transmission from bovid. No significant association was detected between Blastocystis sp. colonization or ST distribution and the symptomatic status of Guinean subjects or the presence of digestive symptoms. In contrast, drilling water consumption represented a significant risk factor for infection by Blastocystis sp. Predominance of ST3 coupled with its low intra-ST diversity strongly suggested large-scale human-to-human transmission of this ST within this cohort. In parallel, the highest intra-ST diversity of ST1 and ST2 was likely correlated with various potential sources of infection in addition to anthroponotic transmission. These findings highlighted the active circulation of the parasite in Guinea as reported in some low-income African countries and the necessity to implement prevention and control measures in order to limit the circulation of this parasite in this endemic geographical area.

First Epidemiological Survey on the Prevalence and Subtypes Distribution of the Enteric Parasite Blastocystis sp. in Vietnam

“…Since this ratio is inversely proportional to intra-ST variability, ST3 exhibited the lowest intra-ST diversity, followed by ST1, ST14, ST10 and ST7. Using the same approach, the lowest sequence variability among ST3 isolates compared to ST1 was also described in surveys conducted in Guinea [ 7 ], Senegal [ 6 ] and Lebanon [ 41 ]. The low number of ST3 genotypes could be undoubtedly correlated to active human-to-human transmission within the Vietnamese population since this ST is not frequently reported in domestic or farm animals.…”

“…The sequences of Blastocystis sp. isolates from the same ST were subsequently aligned against each other using the BioEdit v7.0.1 package (Date of release 10 June 2019; , accessed on 1 February 2022), with the aim to assess the intra-ST diversity and identify the so-called genotypes, as previously described [ 6 , 7 , 31 ].…”

“…Blastocystis sp. is currently the most common intestinal protozoan identified in the human population worldwide [ 1 , 2 , 3 , 4 ] since its prevalence has often been reported to exceed 50% in developing countries from diverse geographical areas and, in particular, in the African continent [ 5 , 6 , 7 ]. This enteric microorganism has also been frequently detected in the gastrointestinal tract of a wide range of animals, including numerous groups of mammals, birds, fish, reptiles and insects [ 8 , 9 , 10 , 11 ].…”

“…Among these STs, 34 of them have been validated, while the remaining 4 STs (ST18-ST20 and ST22) could represent chimaeras arising during Polymerase Chain Reaction (PCR) amplification [ 28 ]. Among all these STs, only 14 (ST1-ST10, ST12, ST14, ST16 and ST23) have been found in the human population, with extremely variable frequencies [ 7 , 29 , 30 , 31 , 32 , 33 ]. Indeed, by globally analyzing the epidemiological data available in numerous countries, ST1 to ST4 represent more than 90% of the subtyped human isolates [ 29 ].…”

Molecular characterization of Blastocystis subtypes in symptomatic patients from the southern region of Syria

“…infection and any gastrointestinal symptoms. It is worth mentioning that half of the samples ~55% in this study were infected with the different STs detected alone, while co-infection with other intestinal parasites were found in 45% of the samples, which leaves the question about the possible real pathogenic potential of this parasite still open [19,58].…”