[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Gastrointestinal tract](https://durgical.com/en/general-pathology/areas/gi/) › Intestinal helminths # Intestinal helminths - Lesion Worms living in the gut can block it, bleed it, cause anaemia or itching, and some invade the wall and the whole body. Updated Nov 12, 2026 ## Key points - Ascaris: eggs from soil; larvae migrate through liver and lungs (pneumonitis), adults in the small bowel; masses of worms obstruct the bowel or bile ducts. - Strongyloides: larvae penetrate skin; autoinfection lets it persist for life; overwhelming hyperinfection with steroids or HTLV-1. - Hookworms (Necator, Ancylostoma): skin entry, attach to the duodenum and suck blood: iron deficiency anaemia. - Trichuris (whipworm) and Enterobius (pinworm) do not invade: heavy whipworm loads cause bloody diarrhoea and rectal prolapse in children; pinworms lay eggs on the perianal skin at night, causing itching (tape test). - Schistosoma: adults in mesenteric veins; eggs trapped in the wall cause granulomas, bleeding and fibrosis; also portal fibrosis. - Tapeworms (Diphyllobothrium, Taenia, Hymenolepis): stay in the lumen; fish tapeworm can cause B12 deficiency. ## What it is Parasitic infections affect more than half of the world's population on a chronic or recurrent basis. Soil-transmitted helminths (Ascaris, Strongyloides, hookworms and whipworm) are common where sanitation is poor, including rural Colombia. Worms that invade tissue provoke eosinophilia; those that stay in the lumen (pinworms, tapeworms) usually do not. Each worm leaves a characteristic lesion. ## Intestinal worms: route, lesion and consequence | Worm | Route | Tissue reaction | Main consequence | | --- | --- | --- | --- | | [Ascaris lumbricoides](https://durgical.com/en/conditions/soil-transmitted-helminthiasis/) | Eggs swallowed | Eosinophil-rich inflammation; lung passage | Bowel or biliary obstruction, liver abscess | | [Strongyloides stercoralis](https://durgical.com/en/conditions/strongyloidiasis/) | Larvae through skin; autoinfection | Eosinophilia, larvae in the mucosa | Lifelong infection, hyperinfection when immunosuppressed | | [Hookworms](https://durgical.com/en/conditions/iron-deficiency-anaemia/) | Larvae through skin | Erosions, focal haemorrhage | Iron deficiency anaemia | | [Trichuris trichiura](https://durgical.com/en/conditions/soil-transmitted-helminthiasis/) | Eggs swallowed | Little invasion | Bloody diarrhoea, rectal prolapse | | Enterobius vermicularis | Eggs, fingers to mouth | None (luminal) | Perianal itching | | Schistosoma (intestinal) | Cercariae through skin | Granulomas around trapped eggs | Bleeding, obstruction, portal fibrosis | | [Tapeworms](https://durgical.com/en/conditions/intestinal-tapeworm-infections/) | Raw or undercooked fish, beef, pork | None (luminal); no eosinophilia | Usually mild; fish tapeworm takes B12 | ## Clinical notes - Before steroids or other immunosuppression, people from endemic regions should be screened or treated for Strongyloides. - Diagnosis is usually by eggs or larvae in stool; pinworm by perianal tape; tapeworm by proglottids. ## Memory aid Invaders bring eosinophils; lodgers in the lumen do not. ## Test yourself Think of the answer, then tap the question to see it. ## Which intestinal worm can complete its life cycle inside the human host, causing lifelong infection? Strongyloides stercoralis, through autoinfection. ## Which worm causes iron deficiency anaemia by attaching to the duodenal mucosa and sucking blood? Hookworms (Necator americanus and Ancylostoma duodenale). ## Which tapeworm can cause vitamin B12 deficiency? Diphyllobothrium latum, the fish tapeworm, which competes for dietary B12. ## Why do tapeworm infections rarely cause eosinophilia? The worm stays in the lumen and does not invade tissue. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/general-pathology/intestinal-helminths/) [More Pathology questions →](https://durgical.com/en/practice/?f=pathology) ## Elsewhere in DurgiPedia - [Eosinophil](https://durgical.com/en/immunology/eosinophil/) ## Connections ## Related 4 - [Infectious enterocolitis](https://durgical.com/en/general-pathology/infectious-enterocolitis/) - [Intestinal protozoa: amoebic flask ulcers, Giardia and Cryptosporidium](https://durgical.com/en/general-pathology/intestinal-protozoa-amoebic-flask-ulcers-giardia-and-cryptosporidium/) - [Acute appendicitis](https://durgical.com/en/general-pathology/acute-appendicitis/) - [Liver infections: bacterial, fungal and parasitic](https://durgical.com/en/general-pathology/liver-infections-bacterial-fungal-and-parasitic/) ## Related conditions 6 - [Soil-transmitted helminthiasis (ascariasis, hookworm, trichuriasis)](https://durgical.com/en/conditions/soil-transmitted-helminthiasis/) - [Strongyloidiasis](https://durgical.com/en/conditions/strongyloidiasis/) - [Intestinal tapeworm infections (taeniasis, hymenolepiasis, diphyllobothriasis)](https://durgical.com/en/conditions/intestinal-tapeworm-infections/) - [Iron deficiency anaemia](https://durgical.com/en/conditions/iron-deficiency-anaemia/) - [Megaloblastic anaemia (B12 or folate deficiency)](https://durgical.com/en/conditions/megaloblastic-anaemia/) - [Rectal prolapse](https://durgical.com/en/conditions/rectal-prolapse/) ## Microorganisms 6 - [Ascaris lumbricoides](https://durgical.com/en/microbiology/ascaris-lumbricoides/) - [Strongyloides stercoralis](https://durgical.com/en/microbiology/strongyloides-stercoralis/) - [Necator americanus / Ancylostoma duodenale](https://durgical.com/en/microbiology/necator-americanus-ancylostoma-duodenale/) - [Trichuris trichiura](https://durgical.com/en/microbiology/trichuris-trichiura/) - [Enterobius vermicularis](https://durgical.com/en/microbiology/enterobius-vermicularis/) - [Schistosoma mansoni / S. haematobium / S. japonicum](https://durgical.com/en/microbiology/schistosoma-mansoni-s-haematobium-s-japonicum/) [← All of general pathology](https://durgical.com/en/general-pathology/) Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Soil-transmitted helminth infections](https://www.who.int/news-room/fact-sheets/detail/soil-transmitted-helminth-infections) (World Health Organization, 2023); [Tapeworm Infections and Cysticercosis](https://www.ncbi.nlm.nih.gov/books/NBK537154/) (StatPearls (NCBI Bookshelf), 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/general-pathology/intestinal-helminths/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/intestinal-helminths/