SK320 U8, Parasitic invertebrates

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SK320 U8, Parasitic invertebrates
2015-01-02 08:50:48

Unit 8, parasitic invertabrates
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  1. Cercaria
    • (Plural cercariae)
    • The larval form of the parasite, developed within the germinal cells of the sporocyst or redia. 
    • A cercariae has a tapering head with large penetration glands; motile carceriae find and settle in the intermediate host, where it becomes either an adult or a metacercaria (species dependent)
  2. Concomitant immunity
    • A condition where the host appears to resist further parasitic infections, even though the adult form survives in their blood.
    • New invading parasites will initiate the immune response.
  3. Cystericus
    Larval stage of the tape worm, consisting of a single invaginated scolex enclosed in a fluid filled cyst.
  4. Definitive host
    The host inside which the parasite reaches reproductive maturity.
  5. DNA Vaccine
    • Injection of "naked" (cell free) DNA encoding pathogenspecific antigens, into the vaccine recipient.
    • DNA is incorporated into muscle DNA, where enough pathogenspecific antigens are synthesised to induce a protective immune response.
  6. Helminths
    • Type of worm, some species of which are parasitic. 
    • Includes Platyhelminthes (flatworms, flukes and tapeworms) and Nematodas (roundworms)
  7. Hyditad cyst
    • Fluid-filled sac within a host tissue, formed by the oncosphere of a tapeworm Echinococcus
    • The sac enlarges gradually, producing protoscolices (juveline tapeworm larvae) which are eventually released from the cyst.
  8. Indirect life cycle
    A parasitic life cycle where an intermediate host of vector is involved; always the case for flukes and tapeworms.
  9. Intermediate host
    • One or more organisms parasitised by juvenile stages of a parasite with a complex life cycle. Harbours a series of larval changes. 
    • E.G shrimp and fish (first and second intermediate hosts) for Anisakis simplex, a nematoda causing abdo pain.
  10. Metacercariae
    • (Singular metacercariae)
    • Cercaria larvae encysted and resting, prior to the parasites being transferred to the definitive host.
  11. Miracidium
    One of the five morphological stages of a fluke. Free -living motile form with celia, which penetrates or is ingested by the intermediate host (mollusc) to become a sporocyte.
  12. Oncosphere
    Egg sac containing six-hooked (hexacanth) larva of tapeworm.
  13. Redia
    • (plural Rediae)
    • A fluke larval form with an oral sucker, it will produce wither more rediae or cercariae.
  14. Schistosomiasis
    • An important human parasitic disease caused by infection by blood flukes of a number of species of Schistosoma.
    • The disease was originally known as bilharzia.
  15. Sporocyst
    An elongated sac that produces a form of parasitic fluke larva (rediae) or, in some cases, more sporocysts.
  16. Vector
    • An agent such as a bacterial plasmid or disabled virus that is used to carry DNA into cells. 
    • The same term is used for an organism that carries a parasite or pathogen from one host to another.