According to the World Health Organization, Approximately 1.5 billion people worldwide are infected with soil-transmitted helminths.

Soil-transmitted helminths (STH) refer to intestinal worms that are transmitted to humans through contaminated soil. The three main species that infect humans are Ascaris lumbricoides (roundworm), Trichuris trichiura (whipworm), and Necator americanus and Ancylostoma duodenale (two species of hookworm). Soil-transmitted helminths live in the intestines, where they produce thousands of eggs a day that are then passed in the feces of infected persons, contaminating the soil in areas where sanitation is poor.

Morbidity resulting from STH infection is directly related to worm burden: Light STH infection usually has no symptoms, while heavy infection contributes to anemia, malnutrition, growth stunting and low birth weight. Moderate to heavy STH infection also leads to impairment of physical and mental growth, delayed educational advancement, and a negative impact on economic development.

Currently, the World Health Organization (WHO) estimates that 267.5 million preschool-aged children and 568.8 million school-aged children require treatment across 103 countries endemic to STH.


  • The greatest burden of disease for STH occurs among the populations in areas that lack access to clean water and sanitation.
  • Moderate to high intensity infections can cause a range of symptoms including diarrhea, abdominal pain, general malaise and weakness, which can then lead to impaired cognitive and physical development.
  • The highest rates of infection occur among pre-school aged children, school-aged children, women of childbearing age, and adults in high-risk occupations such as tea-pickers or miners.
  • The impact of STH infection on women of childbearing age includes maternal anemia, low birth weight and high infant mortality.

Learn more at the WHO Soil Transmitted Helminths page

Control of soil-transmitted helminth infections can be achieved through regular mass drug administration (MDA) with a single dose albendazole or mebendazole.

The WHO recommended strategy for STH control is to conduct regular periodic treatment of all at-risk populations in endemic areas, without previous individual diagnosis.

Currently, USAID provides technical and financial support to 19 STH endemic countries in their efforts to control STH infection. Control efforts for STH within Agency-supported countries have benefited from an integrated MDA strategy, which treats multiple NTDs simultaneously through the combined distribution of safe and effective donated drugs.

This strategy has resulted in significant gains of scaling up MDA and reducing prevalence over the last decade of the Agency program. Looking to the future, the primary focus of Agency support will be to continue to assist countries in maintaining these gains with sustainable STH programs.

The successes achieved to date in the control of STH could not have been achieved without dynamic public-private partnerships. The Agency works closely with a broad range of public and private partners dedicated to the global control of STH. Among these partners are the pharmaceutical companies Johnson & Johnson and GlaxoSmithKline, who provide mebendazole and albendazole through their global donation program to national ministries of health.

Stars At a Glance

Provide support to 19 countries
Provide support to 19 countries