Nematoda

Pseudocoelomates. Body cavitypresent but not lined by mesoderm.

Mostly free living but parasites occur inplants and a variety of animal groups.

Encased in a cuticle which is moulted.Go through 5 stages separated by 4moults.

Parasitic Dorylaimida

• Free living predaceoussoil dwellers.

• Parasitic lineages– Mermithida– Trichurida– Dioctophymatida– Muspiceida

Mermithida:parasites ofarthropods

• Adults free living(sometimes nonfeeding). Matein externalenvironment.Femalescontaminate hosthabitat with eggs.Larvae (J1) infectinsects anddevelop to J4 oradult in host.

Muspiceida

• Parasites of diverse hosts: mice, bats,reindeer, Kangaroo, Koala, Crows.

• Biology poorly known.

Trichurida

• Prominent stichosome: glandular structureassociated with oesophagus.

• Includes:– Trichinella spp.: muscle and intestinal

mucosa/submucosa

– Trichuris spp.: Intestinal submucosa

– Capillaria spp.: variety of sites including intestinalsubmucosa

Trichinella

• Parasites of scavenging life cycles: involvingswine, carnivora (e.g. bear, hyaena), rats,depending on species.

• Humans a frequent accidental host especiallyof T. spiralis.

Capillaria• Parasites of various tissues of all

classes of vertebrates.• Capillaria philippinensis an

accidental parasite in humans inPhilippines.

Life cycles varied:some direct,some involveintermediatehosts.

Trichuris

• Parasites in the submucosaof the posterior gut ofmammals.

• Anterior end embedded intissues: posterior end inlumen.

• Direct life cycle

• Trichuris trichuri in humans; may attain veryhigh intensities (1000+ worms); rectalprolapse, finger clubbing

• T. vulpis in dogs.

• T. suis in swine.

• T. muris in mice.