Parasitic roundworms

The nematodes or roundworms (Phylum Nematoda from Greek νῆμα (nema): "thread" + ode "like") are one of the most common phyla of animals, with over 20,000 different described species (over 15,000 are parasitic). Nematodes commonly parasitic on humans include whipworms, filarids, hookworms, pinworms, ascarids, and horsehair worms.

Hookworms

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  Hookworm lifecycle
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  A hookworm (Ancylostoma caninum) egg.
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  Hookworms

Pinworms

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  Life cycle of Enterobius vermicularis-pinworm
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  Enterobius vermicularis pinworm
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  Head of Enterobius vermicularis
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  Enterobius vermicularis
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  head of a pinworm, colored

See also Enterobius vermicularis

Ascarids

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  Life cycle of Ascaris lumbricoides
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  Fertilized egg of Ascaris lumbricoides
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  Ascaris lumbricoides - adult

Horsehair worms

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  Paragordius tricuspidatus, a horsehair worm-infects insects
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  Spinochordodes tellinii and its grasshopper host

Other

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  Canine roundworm egg.
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  Canine roundworm (Toxascaris leonina) egg.
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  A feline roundworm (Toxocara cati) egg.
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  Strongyloides stercoraliz larva cause of strongyloidiasis.
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  Meloidogyne incognita-plant parasite
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  Heterodera glycines- Root cyst nematode
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  Soybean cyst nematode and egg
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  Nematode teeth