Your Guide to
Neglected Tropical Diseases

Soil-transmitted helminthiasis is a parasitic infectious disease caused by roundworm, whipworm, hookworm that inhabit and parasitize the intestinal tract. It is a chronic disease that spreads from person to person in tropical, subtropical and temperate regions with poor sanitary conditions, either through ingestion of worm eggs present in human faeces or through penetration of the skin by infective larvae found in the soil. These infections damage intestinal health and can cause significant disability by impairing physical and cognitive development in children.

They cause abdominal pain, diarrhoea, weakness and loss of appetite. In severe cases, large masses of worms can accumulate in and block the intestines - sometimes passed in stool in numbers visible to the naked eye - or migrate to the lungs and cause breathing problems. In the case of hookworm infection in particular, blood loss from the intestines leads to chronic, severe anaemia, which is particularly dangerous for adolescent girls and women of childbearing age, and can even be life-threatening.

Three types of parasitic worms cause soil-transmitted helminthiases: roundworms, whipworms and hookworms. These parasites infect humans directly through eggs or larvae in contaminated soil, without passing through intermediate hosts like insects or snails. When infected people lack access to proper sanitation, worm eggs in their faeces contaminate the soil around homes, gardens and fields. The eggs of roundworms and whipworms mature in the soil over several weeks, where they can adhere to vegetables, contaminate water sources and coat children's hands during play. People are infected when they eat unwashed produce, drink contaminated water or touch their mouths with dirty hands. Once ingested, the eggs hatch in the intestines and develop into adult worms.

Hookworms spread differently; their eggs hatch in the soil and larvae penetrate bare feet to enter the bloodstream, maturing into adult worms that live for years in the intestines where they produce thousands of eggs each day.

Geographic scope:

• Among the most common infections worldwide.
• Endemic in more than 100 countries across sub-Saharan Africa, South and Southeast Asia, China, Latin America and the Caribbean.

Population affected:

• Approximately 1.5 billion people are infected with at least one type of soil-transmitted helminth, including over 870 million children requiring treatment.
• Each infects hundreds of millions of people, with roundworms traditionally being the most widespread.

Soil-transmitted helminthiases can be treated with safe, inexpensive medicines (albendazole and mebendazole) given periodically to at-risk populations. WHO recommends treating whole communities once yearly where infection rates exceed 20%, and twice yearly where rates exceed 50%. These medicines eliminate existing worms and reduce soil contamination with eggs, but reinfection occurs quickly after community treatment without improved living conditions.

Long-term prevention requires proper toilets, clean water, handwashing education and wearing shoes to prevent hookworm infection, while raising residents’ awareness through various awareness-raising activities. Deworming programs integrate with schools to prevent millions of infections and protect children from malnutrition and developmental delays. However, complete elimination requires sustained improvements to water, sanitation and hygiene infrastructure.