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Nematoda
Pseudocoelomates. Body cavity present but not lined by mesoderm. Mostly free living but parasites occur in plants and a variety of animal groups.
Encased in a cuticle which is moulted. Go through 5 stages separated by 4 moults.
Parasitic Dorylaimida
• Free living predaceous soil dwellers.
• Parasitic lineages – Mermithida – Trichurida – Dioctophymatida – Muspiceida
Mermithida: parasites of arthropods
• Adults free living (sometimes non feeding). Mate in external environment. Females contaminate host habitat with eggs. Larvae (J1) infect insects and develop to J4 or adult in host.
Muspiceida
• Parasites of diverse hosts: mice, bats, reindeer, Kangaroo, Koala, Crows.
• Biology poorly known.
Trichurida
• Prominent stichosome: glandular structure associated with oesophagus.
• Includes: – Trichinella spp.: muscle and intestinal mucosa/
submucosa – Trichuris spp.: Intestinal submucosa
– Capillaria spp.: variety of sites including intestinal submucosa
Trichinella
• Parasites of scavenging life cycles: involving swine, carnivora (e.g. bear, hyaena), rats, depending on species.
• Humans a frequent accidental host especially of T. Spiralis.
Capillaria • Parasites of various tissues of all
classes of vertebrates. • Capillaria philippinensis an
accidental parasite in humans in Philippines.
Life cycles varied: some direct, some involve intermediate hosts.
Trichuris
• Parasites in the submucosa of the posterior gut of mammals.
• Anterior end embedded in tissues: posterior end in lumen.
• Direct life cycle
• Trichuris trichuri in humans; may attain very high intensities (1000+ worms); rectal prolapse, finger clubbing
• T. vulpis in dogs.
• T. suis in swine.
• T. muris in mice.