title: Comparison of individual and pooled stool samples for the assessment of intensity of Schistosoma mansoni and soil-transmitted helminth infections using the Kato-Katz technique.
abstract: BACKGROUND
  Our group has recently provided a proof-of-principle for the examination of pooled stool samples using McMaster technique as a strategy for the rapid assessment of intensity of soil-transmitted helminth infections (STH, Ascaris lumbricoides, Trichuris trichiura and hookworm). In the present study we evaluated this pooling strategy for the assessment of intensity of both STH and Schistosoma mansoni infections using the Kato-Katz technique.
  
  
  METHODS
  A cross-sectional survey was conducted in 360 children aged 5-18 years from six schools in Jimma Zone (southwest Ethiopia). We performed faecal egg counts (FECs) in both individual and pooled samples (pools sizes of 5, 10 and 20) to estimate the number of eggs per gram of stool (EPG) using the Kato-Katz technique. We also assessed the time to screen both individual and pooled samples.
  
  
  RESULTS
  Except for hookworms, there was a significant correlation (correlation coefficient = 0.53-0.95) between the mean of individual FECs and the FECs of pooled samples for A. lumbricoides, T. trichiura and S. mansoni, regardless of the pool size. Mean FEC were 2,596 EPG, 125 EPG, 47 EPG, and 41 EPG for A. lumbricoides, T. trichiura, S. mansoni and hookworm, respectively. There was no significant difference in FECs between the examination of individual and pooled stool samples, except for hookworms. For this STH, pools of 10 resulted in a significant underestimation of infection intensity. The total time to obtain individual FECs was 65 h 5 min. For pooled FECs, this was 19 h 12 min for pools of 5, 14 h 39 min for pools of 10 and 12 h 42 min for pools of 20.
  
  
  CONCLUSIONS
  The results indicate that pooling of stool sample holds also promise as a rapid assessment of infections intensity for STH and S. mansoni using the Kato-Katz technique. In this setting, the time in the laboratory was reduced by 70 % when pools of 5 instead of individual stool samples were screened.
authors.affiliation: Public Health Laboratory, Southern Nations Nationalities and People's Regional State Health Bureau, Hawassa, Ethiopia. ashenafikure@gmail.com.
authors.forename: Ashenafi
authors.initials: A
authors.lastname: Kure
authors.affiliation: Department of Medical Laboratory Sciences and Pathology, Jimma University, Jimma, Ethiopia. zeleke.mekonnen@ju.edu.et.
authors.forename: Zeleke
authors.initials: Z
authors.lastname: Mekonnen
authors.affiliation: Department of Medical Laboratory Sciences and Pathology, Jimma University, Jimma, Ethiopia. daniel.dana@ju.edu.et.
authors.forename: Daniel
authors.initials: D
authors.lastname: Dana
authors.affiliation: Department of Medical Laboratory Sciences and Pathology, Jimma University, Jimma, Ethiopia. mitiku.bajiro@ju.edu.et.
authors.forename: Mitiku
authors.initials: M
authors.lastname: Bajiro
authors.affiliation: Department of Medical Laboratory Sciences and Pathology, Jimma University, Jimma, Ethiopia. mio.ayana@ju.edu.et.
authors.forename: Mio
authors.initials: M
authors.lastname: Ayana
authors.affiliation: Department of Virology, Parasitology and Immunology, Ghent University, Merelbeke, Belgium. jozef.vercruysse@ugent.be.
authors.forename: Jozef
authors.initials: J
authors.lastname: Vercruysse
authors.affiliation: Department of Virology, Parasitology and Immunology, Ghent University, Merelbeke, Belgium. bruno.levecke@ugent.be.
authors.forename: Bruno
authors.initials: B
authors.lastname: Levecke
mesh_terms: D000293:Adolescent; D000818:Animals; D002648:Child; D002675:Child, Preschool; D005002:Ethiopia / Q000453:epidemiology; D005243:Feces / Q000469:parasitology*; D005260:Female; D006373:Helminthiasis / Q000453:epidemiology / Q000469:parasitology* / Q000635:transmission; D006376:Helminths / Q000302:isolation & purification / Q000502:physiology*; D006801:Humans; D008297:Male; D010270:Parasite Egg Count / Q000379:methods*; D012550:Schistosoma mansoni / Q000302:isolation & purification / Q000502:physiology*; D012555:Schistosomiasis mansoni / Q000453:epidemiology / Q000469:parasitology* / Q000635:transmission; D012987:Soil / Q000469:parasitology*
chemical_list: D012987:Soil