Soil Transmitted Helminths (STH)

The efforts of Children Without Worms (CWW) all center on reducing the global burden of infection by soil-transmitted helminths (STH), a group of intestinal parasites that includes roundworms (Ascaris lumbricoides), whipworms (Trichuris trichuria) and hookworms (Ancylostoma duodenale and Necator americanus). STH infection spreads when people come into contact with feces of an infected individual through dirty hands and contaminated food, or in the case of hookworms, when larvae penetrate the skin. The diagram below demonstrates how STH infection spreads.

STH Transmission












A Disease of Poverty

Globally, up to two billion people are estimated to be infected with one or more of the soil-transmitted helminths (STH). These worms thrive where the soil is warm and humid and where sanitation is inadequate. As a result, this disease disproportionately affects the poor in tropical and sub-tropical countries.

Long-term Impacts of STH Infections

Although the World Health Organization (WHO) estimates that STH infections cause as many as 135,000 deaths a year, the greatest public health significance is the chronic and disabling effects of these infections. Effects include abdominal pain and distension, intestinal obstruction, iron-deficiency anemia, increased susceptibility to other serious infections, stunted growth and impaired cognitive development in children. Ultimately, these conditions may have socio-economic consequences such as poor school performance in children, which in turn leads to decreased labor productivity when these children become adults.

STH Resources

WHO Fact sheet on STH

The Global Atlas of Helminth Infections

Helminth control in school-age children: A guide for managers of control programs (WHO) - PDF file [English] [French] [Russian]

Eliminating STH as a public health problem in children: Progress report 2001-2010 and strategic plan (WHO) - PDF file

WHO Preventive Chemotherapy Databank for STH

World Health Assembly Resolution 54.19 - PDF file [English] [French] [Spanish]