Ascaris lumbricoides (giant roundworm)

Ascaris lumbricoides is a soil-transmitted helminth (parasitic) worm. It is common in tropical and sub-tropical regions and causes a disease called ascariasis.

People become infected when they ingest worm eggs from soil.

It lives and reproduces inside its human host.

The worm cleverly works its way through the body from the gut, via the liver and heart, to the lungs and back to the gut.

Symptoms of the disease vary, and some people don’t even realise they are infected (they are 'asymptomatic').

People infected with multiple worms experience diarrhoea, abdominal pain, general malaise and weakness. These symptoms can affect people’s ability to work and learn, and can impair physical growth.

Species detail

The ascaris worm can reach half a metre in length.

  • A fertilised egg of the Ascaris lumbricoides
    Biology

    Discover how these highly successful worms reproduce in their human hosts and find out more about the ascariasis - the disease they cause.

  • Ascaris worms
    Behaviour

    Ascaris worms have  infected over a billion people world-wide. But how do they do it, and what’s being done to control them?

Images

Life cycle of Ascaris lumbricoides

Life cycle of Ascaris lumbricoides.

© CDC
Global distribution of soil-transmitted helminths including Ascaris

Global distribution of soil-transmitted helminths including Ascaris.

© World Health Organization
A fertilised egg of the Ascaris lumbricoides

A fertilised egg of the Ascaris lumbricoides - fertilised eggs are round and have a thick shell.

© CDC
Ascaris worms

Ascaris worms from one child in Uganda.

© Russell Stothard
Ascaris worms

Ascaris worms.

Ascaris worms

Ascaris worms.

About the author

Dr Martha Betson

Former Post-doc research assistant
Zoology biomedical parasitology research
Department of Zoology

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