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

Dima El Safadi12, Lobna Gaayeb13, Dionigia Meloni14, Amandine Cian1, Philippe Poirier5, Ivan Wawrzyniak5, Frédéric Delbac5, Fouad Dabboussi2, Laurence Delhaes1, Modou Seck3, Monzer Hamze2, Gilles Riveau13 and Eric Viscogliosi1*

Author Affiliations

1 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

2 Centre AZM pour la Recherche en Biotechnologie et ses Applications, Laboratoire Microbiologie, Santé et Environnement, Université Libanaise, Tripoli, Lebanon

3 Biomedical Research Center Espoir pour la Santé (CRB-EPLS), Saint-Louis, Senegal

4 Microbe Division/Japan Collection of Microorganisms (JCM), RIKEN BioResource Center, Tsukuba, Japan

5 Laboratoire Microorganismes: Génome et Environnement, CNRS UMR 6023, Université Blaise Pascal de Clermont-Ferrand, Aubière, France

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BMC Infectious Diseases 2014, 14:164  doi:10.1186/1471-2334-14-164

Published: 25 March 2014



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.


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.


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.


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.

Blastocystis sp; Intestinal parasite; Molecular epidemiology; Pathogenicity; PCR; Subtyping; Transmission; Zoonosis