Children of Senegal River Basin show the highest prevalence of Blastocystissp. ever observed worldwide

Abstract

BackgroundBlastocystis sp. is currently the most common intestinal protist found in human feces and considered an emerging parasite with a worldwide distribution. Because of its potential impact in public health, we reinforced the picture of Blastocystis sp. prevalence and molecular subtype distribution in Africa by performing the first survey of this parasite in Senegal.MethodsStool samples from 93 symptomatic presenting with various gastrointestinal disorders or asymptomatic children living in three villages of the Senegal River Basin were tested for the presence of Blastocystis sp. by non-quantitative and quantitative PCR using primer pairs targeting the SSU rDNA gene. Positive samples were subtyped to investigate the frequency of Blastocystis sp. subtypes in our cohort and the distribution of subtypes in the symptomatic and asymptomatic groups of children.ResultsBy the use of molecular tools, all 93 samples were found to be positive for Blastocystis sp. indicating a striking parasite prevalence of 100%. Mixed infections by two or three subtypes were identified in eight individuals. Among a total of 103 subtyped isolates, subtype 3 was most abundant (49.5%) followed by subtype 1 (28.2%), subtype 2 (20.4%) and subtype 4 (1.9%). Subtype 3 was dominant in the symptomatic group while subtypes 1 and 2 were detected with equal frequency in both symptomatic and asymptomatic groups. The distribution of subtypes was compared with those available in other African countries and worldwide. Comparison confirmed that subtype 4 is much less frequently detected or absent in Africa while it is commonly found in Europe. Potential sources of Blastocystis sp. infection including human-to-human, zoonotic, and waterborne transmissions were also discussed.ConclusionsThe prevalence of Blastocystis sp. in our Senegalese population was the highest prevalence ever recovered worldwide for this parasite by reaching 100%. All cases were caused by subtypes 1, 2, 3 and 4 with a predominance of subtype 3. More than half of the children infected by Blastocystis sp. presented various gastrointestinal disorders. Such high prevalence of blastocystosis in developing countries makes its control a real challenge for public health authorities.

Prevalence and genetic diversity of Blastocystis in family units living in the United States

“…In both instances, infants are Blastocystis negative compared to a high carriage rate in the adult population (Pandey et al, 2015) (Scanlan et al, unpublished). Conversely, in a recent study of 93 children living in the Senegal River Basin, 100% were Blastocystis positive (El Safadi et al, 2014). Interestingly, eight of the nine positives within the adult group were male.…”

“…However, there is considerable variation in prevalence rates between different populations; for example, recent reports have given positive prevalence rates of anywhere between ~24-100% for different populations living in Europe, the Middle East, India and Africa (AbuOdeh et al, 2016;Alfellani et al, 2013;Bart et al, 2013;El Safadi et al, 2014;Krogsgaard et al, 2015;Pandey et al, 2015;Scanlan and Stensvold, 2013;Scanlan et al, 2014). With respect to Blastocystis transmission to humans, three distinct modes of transmission have been proposed (Tan, …”

Prevalence and Risk Factors for Blastocystis Infection Among Children and Caregivers in a Child Care Center, Bangkok, Thailand

“…15,16 Using PCR technique, the highest prevalence of Blastocystis infection was found among children of Senegal River Basin, which was 100%. 17 In this study, direct wet smear and in vitro cultivation were used as screening detection methods. Every fecal sample was cultured in Jones' medium to detect Blastocystis sp., which increased Blastocystis sp.…”

Prevalence and Subtype Identification of Blastocystis sp. in Healthy Individuals in the Tunis Area, Tunisia

“…1,2 Its prevalence considerably varies between geographic areas, reaching 100% in developing countries and 56% in industrialized ones. 3,4 Poor health care and hygiene can explain these differences between countries since its main transmission mode is the fecal-oral route through the consumption of contaminated food or water. 1 It has also been shown that prevalence data may depend on detection methods, especially direct-light microscopy (DLM) of fecal smears versus polymerase chain reaction (PCR) assays.…”