Epidemiology of soil-transmitted helminths following sustained implementation of routine preventive chemotherapy: Demographics and baseline results of a cluster randomised trial in southern Malawi

Stefan Witek-McManus*, James Simwanza, Alvin B. Chisambi, Stella Kepha, Zachariah Kamwendo, Alfred Mbwinja, Lyson Samikwa, William E. Oswald, David S. Kennedy, Joseph W.S. Timothy, Hugo Legge, Sean R. Galagan, Mira Emmanuel-Fabula, Fabian Schaer, Kristjana Hrönn Ásbjörnsdóttir, Katherine E. Halliday, Judd L. Walson, Lazarus Juziwelo, Robin L. Bailey, Khumbo KaluaRachel L. Pullan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Malawi has successfully leveraged multiple delivery platforms to scale-up and sustain the implementation of preventive chemotherapy (PCT) for the control of morbidity caused by soil-transmitted helminths (STH). Sentinel monitoring demonstrates this strategy has been successful in reducing STH infection in school-age children, although our understanding of the contemporary epidemiological profile of STH across the broader community remains limited. As part of a multi-site trial evaluating the feasibility of interrupting STH transmission across three countries, this study aimed to describe the baseline demographics and the prevalence, intensity and associated risk factors of STH infection in Mangochi district, southern Malawi. Between October-December 2017, a community census was conducted across the catchment area of seven primary healthcare facilities, enumerating 131,074 individuals across 124 villages. A cross-sectional parasitological survey was then conducted between March-May 2018 in the censused area as a baseline for a cluster randomised trial. An age-stratified random sample of 6,102 individuals were assessed for helminthiasis by Kato-Katz and completed a detailed risk-factor questionnaire. The age-cluster weighted prevalence of any STH infection was 7.8% (95% C.I. 7.0%-8.6%) comprised predominantly of hookworm species and of entirely low-intensity infections. The presence and intensity of infection was significantly higher in men and in adults. Infection was negatively associated with risk factors that included increasing levels of relative household wealth, higher education levels of any adult household member, current school attendance, or recent deworming. In this setting of relatively high coverage of sanitation facilities, there was no association between hookworm and reported access to sanitation, handwashing facilities, or water facilities. These results describe a setting that has reduced the prevalence of STH to a very low level, and confirms many previously recognised risk-factors for infection. Expanding the delivery of anthelmintics to groups where STH infection persist could enable Malawi to move past the objective of elimination of morbidity, and towards the elimination of STH. Trial registration: NCT03014167.

Original languageEnglish
Article numbere0009292
Pages (from-to)e0009292
JournalPLoS Neglected Tropical Diseases
Issue number5
Publication statusPublished - 12 May 2021

Bibliographical note

Funding Information:
The DeWorm3 Project is funded by a grant from the Bill & Melinda Gates Foundation (OPP1129535) TL, JLW. SK is supported by THRiVE-2, a DELTAS Africa grant #DEL-15-011 from Wellcome Trust grant #107742/Z/15/Z and the UK Government. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Publisher Copyright:
© 2021 Witek-McManus et al.

Other keywords

  • Adolescent
  • Adult
  • Albendazole/therapeutic use
  • Ancylostomatoidea/drug effects
  • Animals
  • Anthelmintics/therapeutic use
  • Child
  • Child, Preschool
  • Communicable Disease Control/methods
  • Cross-Sectional Studies
  • Disease Hotspot
  • Female
  • Hookworm Infections/drug therapy
  • Humans
  • Infant
  • Ivermectin/therapeutic use
  • Malawi/epidemiology
  • Male
  • Mass Drug Administration/methods
  • Soil/parasitology
  • Surveys and Questionnaires


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