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

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

Periodic deworming can be easily integrated with child health days or vitamin A supplementation programmes for preschool-aged children, or integrated with school-based health programmes.

Schools provide an important entry point for deworming activities, as they provide easy access to health and hygiene education components, such as the promotion of hand washing and improved sanitation.

In 2011, over 300 million preschool-aged and school-aged children were treated with anthelminthic medicines in endemic countries, corresponding to 30% of the children at risk.