What are soil-transmitted helminths?

Soil-transmitted helminths (STH) are intestinal worms transmitted through soil contaminated with human faeces. The three main species causing disease: Ascaris lumbricoides (roundworm — infects by ingesting contaminated soil or food); Trichuris trichiura (whipworm — eggs in contaminated soil, ingested); and hookworm (Ancylostoma, Necator — larvae penetrate skin from contaminated soil). Together they infect approximately 1.5 billion people — predominantly in LMICs with poor sanitation.

What is school-based deworming?

School-based deworming delivers albendazole or mebendazole to all school-aged children annually (or twice-yearly in high-transmission areas) through the school system — regardless of individual diagnosis. Schools provide a ready platform to reach the highest-burden age group (5-14 years). The Deworm the World Initiative (EvidenceAction) and WHO school health programmes coordinate school deworming globally. Over 700 million children receive preventive chemotherapy annually through these programmes.

Is deworming effective?

Individual-level treatment definitively cures STH infection and improves haemoglobin and nutritional status in heavily infected children. The controversy is around mass community deworming — the Cochrane review of deworming trials shows modest improvements in weight and haemoglobin in high-infection settings, but effects are smaller than initially expected. The strongest evidence for benefit is in populations with heavy infection and malnutrition. School-based deworming remains WHO-recommended as safe, cheap and beneficial in endemic areas.

How does hookworm cause anaemia?

Adult hookworms (Ancylostoma and Necator) attach to the small intestinal mucosa and feed on blood — each worm consuming approximately 0.03-0.15mL of blood per day. A heavy hookworm infection (1,000+ worms) can cause loss of up to 150mL of blood per day — far exceeding dietary iron replacement capacity. This causes progressive iron-deficiency anaemia, which in pregnant women increases maternal mortality risk and low birthweight.

Who is most affected?

School-aged children (5-14 years) have the highest worm burdens — partly because they play in soil and have more soil-hand-mouth contact. Preschool children (2-5 years) are also at risk. Pregnant women are particularly vulnerable — hookworm anaemia in pregnancy increases maternal and neonatal mortality. Agricultural workers (barefoot field work) are at high occupational risk for hookworm. Communities without latrines and clean water have the highest transmission.

How does GMJ News cover STH?

GMJ News covers WHO deworming programme data, J&J and GSK drug donation milestones, the deworming evidence debate, WASH integration and the STH-malnutrition nexus. STH is part of the GMJ's NTD and child health coverage — relevant to PHIG's global health programme.

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Soil-Transmitted Helminths

Q: How do STH harm children?

STH rarely cause acute illness but have profound cumulative effects: iron-deficiency anaemia (hookworm — causes up to 0.15mL blood loss per worm per day); protein malnutrition (all species compete for nutrients); stunted physical growth; impaired cognitive development and learning; reduced school attendance; and listlessness reducing productivity. The Cochrane review of deworming trials shows that treatment improves weight gain and haemoglobin in highly infected children.

Q: Can STH be eliminated?

WHO's 2030 target is elimination of STH morbidity — reducing heavy-intensity infections to <1% prevalence in children. Complete elimination of STH transmission requires universal access to sanitation (latrines preventing faecal soil contamination) and clean water (handwashing removing infective eggs). Without WASH improvements, dewormed children rapidly reacquire infection from contaminated soil. True elimination therefore requires integrated WASH and deworming — not deworming alone.

GMJ News knowledge hub · last reviewed September 2026 · Georgian Medical Journal

Summary Statistics Glossary GMJ news FAQ Documents Organizations Research

Soil-transmitted helminths (STH) — intestinal worms including roundworm (Ascaris lumbricoides), whipworm (Trichuris trichiura) and hookworm (Ancylostoma, Necator) — infect approximately 1.5 billion people globally, predominantly children who play in and around soil contaminated with human faeces (WHO). STH cause no acute disease but have profound cumulative effects: anaemia, malnutrition, stunted physical growth, impaired cognitive development and reduced school performance — silently stealing children's potential. School-based deworming with albendazole or mebendazole — safe, cheap and scalable — is WHO's primary strategy; over 700 million children per year receive preventive chemotherapy.

Key messages

1.5 billion people infected

Soil-transmitted helminths (STH) infect approximately 1.5 billion people — nearly one in five of the world's population — predominantly in tropical and subtropical low-income communities where open defecation contaminates soil (WHO).

Silent effects on children

STH cause no acute disease but have profound cumulative effects in children: iron-deficiency anaemia, protein malnutrition, stunted physical growth, impaired cognitive development and reduced school attendance and performance — silently stealing educational potential.

School-based deworming saves lives indirectly

WHO recommends school-based and community deworming with albendazole or mebendazole for all at-risk children in endemic areas — interrupting the cycle of infection, anaemia and malnutrition that perpetuates poverty.

WASH is the permanent solution

School-based deworming treats existing infections but children rapidly reacquire worms from contaminated soil. Permanent elimination requires universal WASH: access to latrines (preventing faecal soil contamination) and clean water (handwashing).

Drug donations

Johnson & Johnson donates mebendazole and GlaxoSmithKline donates albendazole for WHO preventive chemotherapy programmes — together enabling over 700 million children to receive deworming annually.

Hookworm and anaemia

Hookworm (Ancylostoma duodenale, Necator americanus) is particularly harmful — adult worms attach to the intestinal wall and feed on blood, each worm consuming approximately 0.03-0.15mL of blood per day. Heavy hookworm infection causes severe iron-deficiency anaemia.

Key statistics

1.5B

people infected with STH

WHO

700M+

children receive preventive chemotherapy/year

WHO

87%

of STH burden in Africa and Asia

WHO/GBD

5-14yr

age group with highest infection intensity

WHO

4.5M

DALYs lost annually to STH

GBD 2019

2030

WHO target: eliminate STH morbidity in children

WHO NTD Roadmap

Children requiring preventive chemotherapy for STH by region (millions) — WHO 2023

Source: WHO. Sub-Saharan Africa and South/Southeast Asia carry the majority of STH burden in children.

Glossary of key terms

Ascaris lumbricoides
WHOThe largest intestinal nematode (roundworm — up to 35cm long). Eggs in soil are ingested; larvae migrate to lungs (causing cough), then are swallowed to mature in the intestine. Heavy infection causes intestinal obstruction, malnutrition and impaired growth.

Trichuris trichiura
WHOWhipworm — infecting the large intestine. Eggs in soil are ingested; adult worms embed in the colonic mucosa. Heavy infection causes Trichuris dysentery syndrome — bloody diarrhoea, rectal prolapse, anaemia and stunted growth.

Hookworm
WHOAncylostoma duodenale and Necator americanus — hookworm larvae penetrate intact skin (from soil contact). Adult worms attach to the small intestinal wall and feed on blood, causing progressive iron-deficiency anaemia. The most anaemia-causing STH.

Preventive chemotherapy (PC)
WHOThe strategy of providing anthelmintic drugs to all members of at-risk groups regardless of individual diagnosis — primarily through school-based programmes. Annual (or twice-annual in high-prevalence areas) albendazole or mebendazole given to school-aged children.

Albendazole
WHO EML/GSKA broad-spectrum benzimidazole anthelmintic — a single 400mg dose treats roundworm and hookworm; less effective against whipworm. Safe from age 1 year. Donated by GlaxoSmithKline for STH and lymphatic filariasis programmes. WHO Essential Medicine.

Mebendazole
WHO EML/J&JA benzimidazole anthelmintic (500mg single dose or 100mg twice daily for 3 days) — treating roundworm, whipworm and hookworm. Donated by Johnson & Johnson for WHO preventive chemotherapy programmes. WHO Essential Medicine.