Quadrigyridae is the only family within Gyracanthocephala, an order of parasitic worms of class Eoacanthocephala. This family contains two subfamilies, ten genera and about 92 species.
The thorny-headed worm family Polymorphidae contains endoparasites which as adults feed mainly in fish and aquatic birds. When this taxon was erected by Meyer in 1931, a subfamily Polymorphinae was established in it. As the Polymorphidae as presently understood would then be monotypic, with no basal genera outside the Polymorphinae, the proposed subfamily is redundant for the time being and therefore most modern treatments simply omit it. Polymorphus minutus is an economically significant parasite in goose and duck farming.
Thelazia is a genus of nematode worms which parasitize the eyes and associated tissues of various bird and mammal hosts, including humans. They are often called "eyeworms", and infestation with Thelazia species is referred to as "thelaziasis". Adults are usually found in the eyelids, tear glands, tear ducts, or the so-called "third eyelid". Occasionally, they are found in the eyeball itself, either under the conjunctiva or in the vitreous cavity of the eyeball. All species of Thelazia for which the life cycle has been studied are transmitted by species of Diptera (flies) which do not bite, but which feed on tears.
Centrorhynchidae is a family of parasitic worms. Three species of these thorny-headed worms in the genus Centrorhynchus were found to parasitize birds of prey and owls Slovakia. These hosts include Buteo buteo, Buteo rufinus, Falco tinnunculus, Asio otus, Strix aluco, Strix uralensis and Tyto alba.
Plagiorhynchidae is a family of parasitic Acanthocephalan worms.
Opisthorchiidae is a family of digenean trematodes. Opisthorchiidae have cosmopolitan distribution.
Polymorphus is a genus of parasitic worms from the phylum Acanthocephala. This group uses amphipod crustaceans as intermediate hosts and various birds as final hosts.
Microcotyle is a genus which belongs to the phylum Platyhelminthes and class Monogenea. Species of Microcotyle are ectoparasites that affect their host by attaching themselves as larvae on the gills of the fish and grow into adult stage. This larval stage is called oncomiracidium, and is characterized as free swimming and ciliated.
Opecoelidae is a family of trematodes. It is the largest digenean family with over 90 genera and nearly 900 species, almost solely found in marine and freshwater teleost fishes. It was considered by Bray et al. to belong in the superfamily Opecoeloidea Ozaki, 1925 or the Brachycladioidea Odhner, 1905.
Camallanus is a genus of parasitic roundworms in the family Camallanidae.
Coitocaecum is a genus of trematodes in the family Opecoelidae. It has been synonymised to Ozakia Wisniewski, 1934, Paradactylostomum Zhukov, 1972 nec Toman, 1992, and Pseudocoitocaecum Bilqees, 1972.
Helicometrina is a genus of trematodes in the family Opecoelidae.
Opistholebes is a genus of trematodes in the family Opecoelidae.
Acanthogyrus is a genus of parasitic worms belonging to the family Quadrigyridae. The species of this genus are found in Africa.
Isthomosacanthidae is a family of parasitic spiny-headed worms.
Porrocaecum is a genus of nematodes belonging to the family Toxocaridae.
Porrorchis is a genus of worms belonging to the family Plagiorhynchidae.
Synhimantus is a genus of nematodes belonging to the family Acuariidae.
Procamallanus is a genus of nematodes belonging to the family Camallanidae.
