title: Two sequential PCR amplifications for detection of Schistosoma mansoni in stool samples with low parasite load.
abstract: Schistosomiasis constitutes a major public health problem, with an estimated 200 million individuals infected worldwide and 700 million people living in risk areas. In Brazil there are areas of high, medium and low endemicity. Studies have shown that in endemic areas with a low prevalence of Schistosoma infection the sensitivity of parasitological methods is clearly reduced. Consequently diagnosis is often impeded due to the presence of false-negative results. The aim of this study is to present the PCR reamplification (Re-PCR) protocol for the detection of Schistosoma mansoni in samples with low parasite load (with less than 100 eggs per gram (epg) of feces). Three methods were used for the lysis of the envelopes of the S. mansoni eggs and two techniques of DNA extraction were carried out. Extracted DNA was quantified, and the results suggested that the extraction technique, which mixed glass beads with a guanidine isothiocyanate/phenol/chloroform (GT) solution, produced good results. PCR reamplification was conducted and detection sensitivity was found to be five eggs per 500 mg of artificially marked feces. The results achieved using these methods suggest that they are potentially viable for the detection of Schistosoma infection with low parasite load.
authors.affiliation: Department of Infectious and Parasitic Diseases, School of Medicine, University of São Paulo, São Paulo, SP, Brazil. cristinasanto@usp.br
authors.forename: Maria Cristina Carvalho do
authors.initials: MC
authors.lastname: Espírito-Santo
authors.forename: Mónica Viviana
authors.initials: MV
authors.lastname: Alvarado-Mora
authors.forename: Pedro Luiz Silva
authors.initials: PL
authors.lastname: Pinto
authors.forename: Flair José
authors.initials: FJ
authors.lastname: Carrilho
authors.forename: João Renato Rebello
authors.initials: JR
authors.lastname: Pinho
authors.forename: Ronaldo Cesar Borges
authors.initials: RC
authors.lastname: Gryschek
mesh_terms: D000818:Animals; D006224:Cricetinae; D018509:DNA, Helminth / Q000302:isolation & purification*; D005243:Feces / Q000469:parasitology*; D006801:Humans; D010270:Parasite Egg Count / Q000379:methods; D059208:Parasite Load; D016133:Polymerase Chain Reaction / Q000379:methods; D012550:Schistosoma mansoni / Q000235:genetics* / Q000302:isolation & purification; D012555:Schistosomiasis mansoni / Q000175:diagnosis* / Q000469:parasitology; D012680:Sensitivity and Specificity
chemical_list: D018509:DNA, Helminth