en.wikipedia.org/wiki/Nematomorpha
3 corrections found
There are a few cases of accidental parasitism in vertebrate hosts, including dogs, cats, and humans.
Horsehair worms are not known to parasitize vertebrates. Reports from humans or pets are treated as accidental encounters or pseudoparasitism, not true infection.
Full reasoning
This sentence is misleading because it describes vertebrate cases as parasitism, but the evidence says horsehair worms do not parasitize vertebrates.
- The University of California IPM program states that horsehair worms "parasitize only invertebrates" and are "harmless to vertebrates," adding that they "can't parasitize people, livestock, pets, or birds" and that if humans ingest them, "infection never occurs."
- The Missouri Department of Conservation likewise says horsehair worms "do not parasitize vertebrate animals," specifically including "people, dogs and cats, livestock, and other mammals, birds, fish, reptiles, or amphibians."
- A 2022 peer-reviewed review/case report in Helminthologia states that published human cases were reviewed by Andreas Schmidt-Rhaesa and that, aside from a few unexplained reports, "there was no true parasitism and the association between humans and gordiids was accidental." The same paper concludes: "there is no evidence for a parasitation of humans by gordiid worms."
So while worms may occasionally be found near or in human-associated settings (or passed accidentally after ingestion), calling those vertebrate cases "parasitism" is incorrect.
3 sources
- Horsehair Worms / Home and Landscape / UC Statewide IPM Program (UC IPM)
Horsehair worms parasitize only invertebrates such as insects and are harmless to vertebrates... Horsehair worms are harmless to vertebrates, because they can't parasitize people, livestock, pets, or birds... infection never occurs.
- Horsehair Worms | Missouri Department of Conservation
Horsehair worms are not considered harmful to people, dogs and cats, livestock, and other mammals, birds, fish, reptiles, or amphibians, because they do not parasitize vertebrate animals.
- Human Encounter with a Horsehair Worm (Nematomorpha): Is There a Reason To Worry?
The reported cases were reviewed... who came to the conclusion that... there was no true parasitism and the association between humans and gordiids was accidental... In summary, there is no evidence for a parasitation of humans by gordiid worms.
The five marine species of nematomorph are contained in Nectonematoida.
This species count is out of date. A sixth marine Nectonema species, Nectonema shimadai, was described in 2026.
Full reasoning
This statement is no longer correct.
A 2026 Journal of Helminthology paper says that before its new description, "There are currently five named species" in the marine genus Nectonema. The same paper then says, "we here describe as a new species" Nectonema shimadai sp. nov. Because Nectonema is the sole marine genus of Nematomorpha, that publication raises the number of named marine nematomorph species from five to at least six.
So the article's claim that there are only five marine species in Nectonematoida is outdated and incorrect.
1 source
- A new Nectonema nematomorph species parasitic in an alpheid shrimp (Decapoda: Caridea)
There are currently five named species... During a faunal survey around Kikaijima Island, Japan, the second author collected one shrimp parasitised by a Nectonema nematomorph, which we here describe as a new species.
The approximately 320 remaining species are distributed between two families, within the monotypic class Gordioida.
The gordiid/freshwater side of Nematomorpha has more than 350 described species, not about 320.
Full reasoning
The species count here is too low.
A 2023 peer-reviewed paper in International Journal of Molecular Sciences summarizes the phylum as follows: marine Nectonematoida has "one genus, five species" and freshwater Gordioidea has "20 genera, more than 350 species." That directly contradicts the article's claim that the non-marine remainder is only "approximately 320" species.
In other words, the currently described freshwater/gordiid diversity is well above 320.
1 source
- Expression of Hairpin-Enriched Mitochondrial DNA in Two Hairworm Species (Nematomorpha)
Currently, the phylum Nematomorpha comprises two classes: marine Nectonematoida (one genus, five species) and freshwater Gordioidea (20 genera, more than 350 species).