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Nematodes are very small, slender worms. Most are free-living, often less than 2.5 mm long and some only about 1 mm. Many nematodes are microscopic. Some soil nematodes can reach up to 7 mm in length, and some marine species can reach up to 5 cm. Some are parasitic and can reach lengths of 50 cm or more. [42]
Worms vary in size from microscopic to over 1 metre (3.3 ft) in length for marine polychaete worms (bristle worms); [1] 6.7 metres (22 ft) for the African giant earthworm, Microchaetus rappi; [2] and 58 metres (190 ft) for the marine nemertean worm (bootlace worm), Lineus longissimus. [3]
The pinworm has a worldwide distribution, [25] and is the cause of the most common helminthiasis (parasitic worm infection) in the United States, western Europe, and Oceania. [21] In the United States, a study by the Center of Disease Control reported an overall incidence rate of 11.4% among children. [ 21 ]
Diagnosis is often made by visible recognition of the worm moving through the tissue of the buccal cavity by either patient or doctor. Also, recovery of worm from patient is also a diagnostic technique. Microscopic identification of worm removed from patient's mouth or tissue is another diagnostic technique for determining the parasite infection.
Main article: Human parasite Endoparasites Protozoan organisms Common name of organism or disease Latin name (sorted) Body parts affected Diagnostic specimen Prevalence Source/Transmission (Reservoir/Vector) Granulomatous amoebic encephalitis and Acanthamoeba keratitis (eye infection) Acanthamoeba spp. eye, brain, skin culture worldwide contact lenses cleaned with contaminated tap water ...
Demodex folliculorum is a microscopic mite that can survive only on the skin of humans. [2] [3] Most people have D. folliculorum on their skin.Usually, the mites do not cause any harm, so are considered an example of commensalism rather than parasitism; [4] but they can cause disease, known as demodicosis.
The worms that reproduce through self-fertilization are at risk for high linkage disequilibrium, which leads to lower genetic diversity in populations and an increase in accumulation of deleterious alleles. [32] In C. elegans, somatic sex determination is attributed to the tra-1 gene. [33]
Nematomorpha (sometimes called Gordiacea, and commonly known as horsehair worms, hairsnakes, [1] [2] [3] or Gordian worms) are a phylum of parasitoid animals superficially similar to nematode worms in morphology, hence the name. Most species range in size from 50 to 100 millimetres (2.0 to 3.9 in), reaching 2 metres (79 in) in extreme cases ...