The optimal timing of post-treatment sampling for the assessment of anthelminthic drug efficacy against Ascaris infections in humans

Int J Parasitol Drugs Drug Resist. 2018 Apr;8(1):67-69. doi: 10.1016/j.ijpddr.2017.12.004. Epub 2018 Jan 13.


The egg reduction rate (ERR) is the current standard mean to assess the efficacy of drugs against human soil-transmitted helminths (STHs; Ascaris lumbricoides, Trichuris trichiura and hookworm). Although the timing of post-treatment sampling is pivotal for a readily interpretation of drug efficacy, there is lack empirical data that allows recommending the optimal time point for a follow-up egg counting. In the present study, we re-analyzed both the kinetics of worm expulsion and egg output for Ascaris lumbricoides following a single oral dose of albendazole in a series of studies previously conducted in Kenyan communities. The results indicate that it takes up to 10 days post-treatment before the expulsion of both adult male and female Ascaris worms is completed, approximately 20% of the worms being expelled between day 7 and 10 post-treatment. The sequential analysis of the egg out put, indicated a poor ERR (89.4%) at day 7 post-treatment, but a 100% ERR at day 14 and 21 post-treatment. Based on our findings we recommend to wait at least 14 days after an albendazole treatment before conducting the follow-up egg count. Any sampling before this time point may result in biased ERR estimates, due the release of residual eggs from moribund or degenerating worms.

Keywords: Albendazole; Anthelmintic resistance; Ascaris lumbricoides; Egg reduction rate; Worm expulsion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Albendazole / administration & dosage
  • Albendazole / therapeutic use*
  • Animals
  • Anthelmintics / administration & dosage
  • Anthelmintics / therapeutic use*
  • Ascariasis / drug therapy*
  • Ascariasis / epidemiology
  • Ascariasis / parasitology
  • Ascaris lumbricoides / drug effects*
  • Child
  • Drug Resistance
  • Feces / parasitology
  • Female
  • Humans
  • Kenya / epidemiology
  • Male
  • Parasite Egg Count / methods*
  • Specimen Handling
  • Time Factors


  • Anthelmintics
  • Albendazole