e-Library of Evidence for Nutrition Actions (eLENA)

Deworming to combat the health and nutritional impact of helminth infections

Helminths are a group of parasites commonly referred to as worms and include schistosomes and soil-transmitted helminths. Schistosome and soil-transmitted helminth infections are among the most common infections in developing countries and can impair nutritional status by causing:

  • internal bleeding which can lead to loss of iron and aenemia;
  • malabsorption of nutrients;
  • diarrhoea; and
  • loss of appetite which can lead to a reduction in energy intake.

Infections can also cause cognitive impairment as well as tissue damage that may require corrective surgery.

The nutritional impairment caused by schistosome and soil-transmitted helminth infections during childhood has been shown to have a significant impact on growth and development of children. Periodic treatment (deworming) of children together with improvement of water and sanitation, and health education can reduce the transmission of schistosome and soil-transmitted helminth infections.

WHO recommendations

WHO recommends periodic treatment with anthelminthic (deworming) medicines, without previous individual diagnosis to all at-risk people living in endemic areas.

People at risk are:

  • preschool-aged children
  • school-aged children
  • women of childbearing age (including pregnant women in the second and third trimesters and breastfeeding women)

Treatment should be given once a year when the prevalence of soil-transmitted helminth infections in the community is over 20%, and twice a year when the prevalence of soil-transmitted helminth infections in the community exceeds 50%. This intervention reduces morbidity by reducing the worm burden.

In addition:

  • education on health and hygiene reduces transmission and reinfection by encouraging healthy behaviours;
  • provision of adequate sanitation is also important but not always possible in resource-constrained settings.


Additional information can be found in the guidance documents under 'WHO documents' below.

WHO documents

GRC-approved guidelines

Status: not currently available

Other guidance documents


Related Cochrane reviews
Other related systematic reviews
Clinical trials

Last update:

23 April 2016 16:12 CEST

Category 2 intervention

Systematic review(s) have been conducted but no recent guidelines yet available that have been approved by the WHO Guidelines Review Committee