Parasitic worms (soil-transmitted helminths)

Soil-transmitted helminths are parasitic worms that infect humans who come into contact (either by eating contaminated food or by walking barefoot in infected areas) with worm eggs or larva in soil. These worms live in the intestines (guts) and their eggs pass into soil from faeces (human waste) when infected humans defecate outside or when human waste is used as a crop fertiliser.

They are one of the commonest infections worldwide, especially in hot, humid areas where sanitation and hygiene are poor. There is no direct person-to-person spread or transmission via fresh faeces, as the eggs need about three weeks in soil before they become infectious.

The main soil-transmitted helminths that infect people are: hookworms (Necator americanus and Ancylostoma duodenale), roundworms (e.g. Ascaris lumbricoides) and whipworms (Trichuris trichiura).

Humans get infected with roundworm or whipworm by eating fruit and vegetables that have not been carefully cooked, washed or peeled. The eggs can also be spread by dirty cooking utensils and by putting hands or fingers contaminated with dirt into the mouth.

Symptoms include abdominal pain, appetite loss, diarrhoea and general weakness. Hookworms can also cause anaemia if bleeding from the intestines occurs. Long-term infection can stop food being absorbed properly and can cause complications, such as intestinal obstruction, that needs surgery.

A type of hookworm infection sometimes seen in travellers is Cutaneous Larvae Migrans. Skin contact with soil or sand contaminated with hookworm larvae in animal (e.g. dog or cat) faeces can result in an itchy, red tracking of the skin, which moves as the larvae migrate about the skin.

Drug treatment, with mebendazole or albendazole, is safe and effective.

Prevention

There is no vaccine or drug to prevent infection. Avoiding food that may be contaminated with soil or human faeces by following good food, water and personal hygiene advice helps protect against roundworm and whipworm infection.

Travellers should avoid walking barefoot in regions where hookworm is common, including beaches and any area that may have been contaminated with human and animal waste.

Travellers who are immunocompromised are at risk of overwhelming infection with Strongyloides stercoralis so good prevention measures are particularly important. 

Resources

First published : 15 July 2019 Last updated : 15 May 2024

Explore more

Hepatitis B

Hepatitis B is a viral infection of the liver transmitted by contact with the blood or body fluids of an infected person

Updated: 20 November 2024

Chikungunya

Chikungunya is a viral infection caused by the chikungunya virus (CHIKV) and is transmitted through the bite of an infected mosquito

Updated: 12 November 2024

Marburg virus disease

Marburg virus is an animal-borne (zoonotic) virus that can cause a severe and often fatal haemorrhagic fever called Marburg virus disease (MVD)

Updated: 06 November 2024

Leishmaniasis

Leishmaniasis is an infection transmitted by the bite of infected phlebotomine sandfly

Updated: 06 November 2024

Lassa fever

Lassa fever is an infectious disease caused by Lassa virus, a member of the arenavirus family

Updated: 06 November 2024

Featured Topics

Lassa fever

Lassa fever is an infectious disease caused by Lassa virus, a member of the arenavirus family

Updated: 06 November 2024

Malaria

Malaria is a serious and sometimes fatal disease, transmitted by the bite of an infected mosquito occurring in many tropical regions of the world

Updated: 20 January 2024

Measles

Measles is a highly infectious viral illness with the potential for serious and life threatening complications

Updated: 19 June 2024

Mpox

Mpox is an infectious disease caused by the virus MPXV

Updated: 17 September 2024

Oropouche virus disease

Oropouche virus disease is an arboviral disease caused by the Oropouche virus (OROV) spread to humans mainly through the bite of an infected midge

Updated: 24 October 2024

Pertussis

Pertussis, also known as whooping cough is typically spread by the respiratory route when, for example, an infected person coughs or sneezes

Updated: 09 March 2024