Schistosoma mansoni in schoolchildren in a Madagascan highland school assessed by PCR and sedimentation microscopy and Bayesian estimation of sensitivities and specificities

Acta Trop. 2014 Jun;134:89-94. doi: 10.1016/j.actatropica.2014.03.003. Epub 2014 Mar 19.


Madagascar is an endemic area for schistosomiasis, but recent prevalence data are scarce. We investigated stool samples of 410 children aged 4-18 years from a combined primary and secondary school in a Madagascan highland village near Ambositra in order to assess the prevalence of Schistosoma mansoni using microscopy and real-time polymerase chain reaction (PCR). A high prevalence of S. mansoni of 77.1% was detected by PCR, while only 15.2% of microscopic examinations of sedimentation-enriched stools were positive. We estimated the sensitivity and specificity of stool sedimentation microscopy (19.7% and 98.8%) and of PCR (98.9% and 89.3%) using a Bayesian approach for two dependant tests in one population without a reference standard. Our Bayesian posterior estimate of the prevalence is 80.2%. Simple sedimentation technique misses about 4/5 of all PCR-confirmed infections and is insufficient to determine the prevalence of S. mansoni. A survey comparing PCR with a classical standard technique (KatoKatz) is desirable.

Keywords: Madagascar; Microscopy; PCR; Prevalence; Schistosomiasis; Sensitivity and specificity.

Publication types

  • Comparative Study
  • Evaluation Study

MeSH terms

  • Adolescent
  • Animals
  • Child
  • Cross-Sectional Studies
  • Diagnostic Tests, Routine / methods*
  • Female
  • Humans
  • Madagascar / epidemiology
  • Male
  • Microscopy / methods*
  • Parasitology / methods*
  • Polymerase Chain Reaction / methods*
  • Prevalence
  • Schistosoma mansoni / isolation & purification*
  • Schistosomiasis mansoni / diagnosis*
  • Schistosomiasis mansoni / epidemiology*
  • Schools
  • Students