title: Children of Senegal River Basin show the highest prevalence of Blastocystis sp. ever observed worldwide.
abstract: BACKGROUND
  Blastocystis 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.
  
  
  METHODS
  Stool 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.
  
  
  RESULTS
  By 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.
  
  
  CONCLUSIONS
  The 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.
authors.forename: Dima
authors.initials: D
authors.lastname: El Safadi
authors.forename: Lobna
authors.initials: L
authors.lastname: Gaayeb
authors.forename: Dionigia
authors.initials: D
authors.lastname: Meloni
authors.forename: Amandine
authors.initials: A
authors.lastname: Cian
authors.forename: Philippe
authors.initials: P
authors.lastname: Poirier
authors.forename: Ivan
authors.initials: I
authors.lastname: Wawrzyniak
authors.forename: Frédéric
authors.initials: F
authors.lastname: Delbac
authors.forename: Fouad
authors.initials: F
authors.lastname: Dabboussi
authors.forename: Laurence
authors.initials: L
authors.lastname: Delhaes
authors.forename: Modou
authors.initials: M
authors.lastname: Seck
authors.forename: Monzer
authors.initials: M
authors.lastname: Hamze
authors.forename: Gilles
authors.initials: G
authors.lastname: Riveau
authors.affiliation: Institut Pasteur de Lille, Centre d'Infection et d'Immunité de Lille (CIIL), Inserm U1019, CNRS UMR 8204, Université Lille Nord de France, 1 rue du Professeur Calmette, BP 245, 59019 Lille cedex, France. eric.viscogliosi@pasteur-lille.fr.
authors.forename: Eric
authors.initials: E
authors.lastname: Viscogliosi
mesh_terms: D016844:Blastocystis / Q000235:genetics / Q000302:isolation & purification*; D016776:Blastocystis Infections / Q000453:epidemiology* / Q000469:parasitology; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005243:Feces / Q000469:parasitology; D005260:Female; D014943:Global Health; D006801:Humans; D008297:Male; D017720:Molecular Epidemiology; D015995:Prevalence; D045483:Rivers; D012675:Senegal / Q000453:epidemiology