Mathematical inference on helminth egg counts in stool and its applications in mass drug administration programmes to control soil-transmitted helminthiasis in public health

Adv Parasitol. 2015 Mar;87:193-247. doi: 10.1016/bs.apar.2015.01.001. Epub 2015 Feb 14.


In the present study, we present a hierarchical model based on faecal egg counts (FECs; expressed in eggs per 1g of stool) in which we first describe the variation in FECs between individuals in a particular population, followed by describing the variance due to counting eggs under a microscope separately for each stool sample. From this general framework, we discuss how to calculate a sample size for assessing a population mean FEC and the impact of an intervention, measured as reduction in FECs, for any scenario of soil-transmitted helminth (STH) epidemiology (the intensity and aggregation of FECs within a population) and diagnostic strategy (amount of stool examined (∼sensitivity of the diagnostic technique) and examination of individual/pooled stool samples) and on how to estimate prevalence of STH in the absence of a gold standard. To give these applications the most wide relevance as possible, we illustrate each of them with hypothetical examples.

Keywords: Anthelminthic resistance; Faecal egg counts; Hierarchical model; Mass drug administration; Monitoring system; Sample size; Soil-transmitted helminths; Survey design; True prevalence.

MeSH terms

  • Animals
  • Anthelmintics / therapeutic use*
  • Feces / parasitology*
  • Helminthiasis / drug therapy*
  • Helminthiasis / epidemiology
  • Helminthiasis / parasitology
  • Helminthiasis / prevention & control*
  • Helminths / physiology
  • Humans
  • Models, Theoretical*
  • Parasite Egg Count
  • Soil / parasitology*


  • Anthelmintics
  • Soil