[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › Nematodes [Microbiology](https://durgical.com/en/microbiology/) · [Parasites](https://durgical.com/en/microbiology/#d-parasite) # Nematodes - Parasites Roundworms: gut worms caught from soil (soil-transmitted helminths), pinworms, and tissue worms such as filariae, Toxocara and Trichinella. Updated 2026-11-01 ## What they are Nematodes are cylindrical, unsegmented worms with separate sexes and a complete gut. Some live in the bowel and spread through soil or hand to mouth; others live in tissues and arrive through insects or undercooked meat. ## What they share - Cylindrical, unsegmented body with a cuticle. - Separate sexes (except the parthenogenetic Strongyloides female). - Soil-transmitted helminths: Ascaris, Trichuris, hookworms and Strongyloides. - Several pass through the lungs (Ascaris, hookworms, Strongyloides). - Filariae are insect-borne and many carry the bacterium Wolbachia. ## Key points - Ascaris, hookworms and Strongyloides pass through the lungs (Löffler); Trichuris and Enterobius do not. - Through the skin: hookworms and Strongyloides; by mouth: Ascaris, Trichuris and Enterobius. - Benzimidazoles for soil-transmitted helminths; ivermectin for Strongyloides and onchocerciasis. - Periodic school deworming is the WHO and Colombian strategy. - Eosinophilia: a clue to helminths migrating through tissue. ## Microorganisms in this group - [**Ascaris lumbricoides** The largest human gut worm. People swallow its eggs from soil; in children with many worms it can block the bowel. Exam priority: high](https://durgical.com/en/microbiology/ascaris-lumbricoides/) - [**Necator americanus / Ancylostoma duodenale** Worms that enter through bare feet, latch onto the gut and suck blood: they cause iron-deficiency anaemia, mostly in children. Exam priority: high](https://durgical.com/en/microbiology/necator-americanus-ancylostoma-duodenale/) - [**Strongyloides stercoralis** A worm that reinfects its host and can live in the body for decades. Under steroids it multiplies out of control and can cause fatal infection. Exam priority: high](https://durgical.com/en/microbiology/strongyloides-stercoralis/) - [**Trichuris trichiura** A whip-shaped colon worm, the commonest soil-transmitted helminth in Colombian schoolchildren; heavy loads cause dysentery and rectal prolapse. Exam priority: high](https://durgical.com/en/microbiology/trichuris-trichiura/) - [**Enterobius vermicularis** A tiny white worm that lays eggs around the anus at night and causes itching. Very common in children; it spreads at home and at school. Exam priority: high](https://durgical.com/en/microbiology/enterobius-vermicularis/) - [**Toxocara canis / Toxocara cati** A roundworm of dogs and cats. A child who swallows its eggs from soil can have larvae wandering through liver, lung or eye, with no adult worm. Exam priority: medium](https://durgical.com/en/microbiology/toxocara-canis-toxocara-cati/) - [**Ancylostoma braziliense / Ancylostoma caninum** A dog and cat hookworm. Its larva enters the skin on sandy beaches and leaves a red, winding, very itchy track. Exam priority: medium](https://durgical.com/en/microbiology/ancylostoma-braziliense-ancylostoma-caninum/) - [**Wuchereria bancrofti / Brugia malayi** A mosquito-borne worm that lives in lymph vessels. Over the years it causes massive leg swelling (elephantiasis) and hydrocele. Exam priority: medium](https://durgical.com/en/microbiology/wuchereria-bancrofti-brugia-malayi/) - [**Onchocerca volvulus** A worm spread by a blackfly of fast rivers; it damages skin and eyes and can blind. Colombia was the first country in the world to eliminate it. Exam priority: medium](https://durgical.com/en/microbiology/onchocerca-volvulus/) - [**Trichinella spiralis** A tiny worm that comes with undercooked pork or game. Its larvae encyst in muscle and cause fever, muscle pain and swollen eyelids. Exam priority: medium](https://durgical.com/en/microbiology/trichinella-spiralis/) - [**Mansonella ozzardi / Mansonella perstans** An Amazonian filaria spread by biting midges. It rarely causes symptoms, but its microfilariae show up on thick smears and must be told apart. For completeness](https://durgical.com/en/microbiology/mansonella-ozzardi-mansonella-perstans/) ## Test yourself Think of the answer, then tap the question to see it. ## Which intestinal nematodes pass through the lungs? Ascaris lumbricoides, hookworms and Strongyloides stercoralis. ## Which soil-transmitted helminths enter through the skin? Hookworms and Strongyloides stercoralis, via filariform larvae in soil. ## Which drugs are used in mass school deworming? Benzimidazoles: albendazole or mebendazole. ## Which filarial endosymbiont is targeted by doxycycline? Wolbachia. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/groups/nematodes/) [← All of microbiology](https://durgical.com/en/microbiology/) Educational content on microorganisms; not a 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) (WHO, 2023); [Geohelmintiasis](https://minsalud.gov.co/salud/publica/PET/Paginas/geohelmintiasis.aspx) (Ministerio de Salud y Protección Social de Colombia, 2014); [Lymphatic filariasis](https://www.who.int/news-room/fact-sheets/detail/lymphatic-filariasis) (WHO, 2024); [CDC - DPDx - Strongyloidiasis](https://www.cdc.gov/dpdx/strongyloidiasis/index.html) (CDC, 2019). ## **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/microbiology/groups/nematodes/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/groups/nematodes/