What are intestinal worms?

Intestinal worms, also called ‘soil-transmitted helminth infections’ or STH, are part of a group of parasitic and bacterial conditions known as neglected tropical diseases.

A woman crouches in a stream using a bucket to collect water in Nigeria.

Helminths are worm-like intestinal parasites that live inside the digestive tract and feed off nutrients from their host, causing the infected person to become malnourished and susceptible to disease and chronic illness.

Adult worms live in a person’s intestine, where they produce thousands of eggs each day. The infection is spread when eggs, passed in human faeces, contaminate soil – a problem that is particularly prevalent in poor communities with inadequate sanitation. The eggs can be ingested when contaminated soil is found on unwashed vegetables, water sources or unwashed hands. In some cases, hookworms can penetrate the skin, typically on the hands and feet, and cause infection.

At first, symptoms of intestinal worms may be mild or non-existent, but infections can lead to diarrhoea, abdominal pain, weakness, impaired cognitive and physical development, anaemia and nutritional problems. In severe cases, STH can cause death.

As well as the significant physical symptoms, intestinal worms can decrease the quality of life of people affected, with negative long-term effects on employment, education, fertility and happiness. Children may be forced to miss school, damaging their education and development.

1.5 billion
people worldwide are infected with intestinal worms
aged about three to eight are most at risk
600 million
school-age children live in at-risk areas

How are intestinal worms treated?


STH is treated through a single dose of deworming medicine, either Albendazole® donated by GlaxoSmithKline, or Mebendazole® donated by Johnson and Johnson.

Volunteer community drug distributors are shown how to use measuring sticks to calculate drug dosages.


Medication is distributed to schools and communities. Specially trained school teachers play a key role in distributing and administering these vital treatments.

A close-up of a child washing their hands under a water tap.


We incorporate hygiene education into our deworming programmes. Access to clean water and sanitation, as well as good hygiene behaviour, is vital to prevent STH spreading.

What we’re doing

Sightsavers aims to control intestinal worms by 2020 in the countries in which we’re running deworming programmes. These countries include Cameroon, Democratic Republic of Congo, Nigeria and Guinea.

Soil-transmitted helminths can cause symptoms such as anaemia, intestinal obstruction, inflammation of the colon, impaired development, and death. These significantly decrease the quality of life of those affected and can have negative long-term effects on employment, education, fertility and happiness. We aim to use our NTD programmes to target entire communities of at-risk men, women and children to eliminate these diseases.

In 2016, Sightsavers treated more than 16.5 million people for soil-transmitted helminths. In the same year we trained more than 235,000 volunteer community drug distributors to distribute treatments to everyone in their local communities. Medication is distributed to schools and communities to kill and prevent the spread of helminths. The disease is often treated at the same time as schistosomiasis.

Sightsavers also incorporates hygiene education into community and school-based programmes, and coordinates with WASH (water, sanitation and hygiene) programmes. Access to and use of clean water and sanitation, along with following good hygienic behaviours such as wearing shoes, is critical to the prevention and control of intestinal worms.

Find out about other diseases we treat

Neglected tropical diseases

More about intestinal worms

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