SGU Parasit 1

  1. What is a parasite?
    • An organism that lives in or on another organism of a different species (host).
    • Usually harmful

  2. What is parasitism?
    A kind of symbiotic relationship between two different species of organisms in which the parasite is metabolically dependent on the host.
  3. What is a facultative parasite?
    • An organism that is capable of living either a free or parasitic existence.
    • The threadworm Strongyloides stercoralis in dogs or humans.
  4. What are helminths?
    Roundworms or nematodes (e.g., ascarids) and flatworms (e.g., tapeworms or cestodes) and flukes or trematodes.
  5. What is a pseudoparasite?
    An object (e.g., pollen) or nonparasitic organism (e.g., grain mite) that is mistaken for a "true" parasite.
  6. Definitive host
    An obligatory host in which a parasite develops to sexual maturity.
  7. Intermediate host
    An obligatory host in the life cycle of a parasite in which immature or asexual stages undergo essential development and/or proliferation before transmission to the definitive host (e.g., mosquitos).
  8. Mechanical vector
    A nonessential host which passively carries infective parasite stages on its body; source of parasite contamination (e.g., boot, syringe).
  9. Biological vector
    Usually an arthropod (e.g., face fly); may be an intermediate host or mechanical vector.
  10. Paratenic host
    • AKA Transport host - a nonessential host (e.g., rodents, roach), in the life cycle of a parasite capable of harboring and maintaining immature stages
    • Parasites undergo NO development or proliferation within these hosts but are merely carried within the body until consumed by its proper definitive host.
  11. Reservoir host
    A population of infected hosts which serve as a potential source of infection for other species of susceptible domestic animals or humans (e.g., wild [feral] animals)
  12. Infective stage
    Developmental stage of a parasite capable of initiating a new infection within another host (e.g., eggs, oocysts, larvae).
  13. Direct life cycle
    Transmission of parasitic infection from one host to another without the requirement of an intermediate host; one-host life cycle.
  14. Indirect life cycle
    Transmission of parasitic infection from one host animal to another through one or more essential intermediate hosts; multi-host life cycle.
  15. Pre-patent period
    The time between ingestion and invasions of infective stages of a helminth parasite in its definitive host until eggs or larvae are first produced (e.g., the time between ingestion of infective L3 nematode larvae until the appearance of eggs in the feces).
  16. Patent period
    The life span of the adult parasite in the host.
  17. Infection
    Establishment of a parasite within a host, with or without clinical signs; genrally endoparasites infect their hosts (e.g., nematodes, cestodes and flukes).
  18. Infestation
    Establishment of a parasite on the surface of a host with or without development of clinical signs. Ectoparasites infest their hosts (e.g., insects and arachnids).
  19. Acute disease
    • Rapid onset
    • Large parasite numbers
    • Usually dramatic clinical signs (e.g., anemia, death)
  20. Chronic disease
    • Slow debilitation
    • Small to moderate parasite numbers
    • Clinical signs usually slow in developing
  21. Subclinical infection
    • No clinical signs are manifested
    • May be detected by decreased growth, loss of production, etc.
    • 85% subclinical
  22. Ways parasites injure their hosts
    • They feed on blood, lymph or exudate (e.g. mosquitoes, flies)
    • They feed on solid tissues
    • They compete with the host for nutrition by ingestion or absorption through the body wall
    • They may cause mechanical obstruction of intestines, etc.
    • They may produce pressure atrophy
    • They may destroy host cells by growing in them
    • They may produce toxic substances
    • They may produce allergic reactions, e.g. flea allergy
    • They may produce host reactions
    • They may directly/indirectly promote the neoplastic transformation of cells
    • They may carry diseases and parasites, e.g. malaria, heartworm
    • They may reduce their host’s resistance to other diseases and parasites
  23. Characteristics of insects
    • Antennae: single pair
    • Body segments: 3
    • Legs: 6
    • Wings: often found
  24. Characteristics of arachnids
    • Antennae: none
    • Body segments: 2
    • Legs: 8
    • Wings: wingless
  25. Simple metamorphosis
    • Egg > Nymph > Adult
    • Nymphal stage resembles the adult
    • Nymphs are smaller and do not possess wings
    • Nymphs are not sexually mature, they cannot reproduce
    • Ex: the cockroach
  26. Complex metamorphosis
    • Egg > Larva > Pupa > Adult
    • Each of these developmental stages bears no resemblance to the adult
    • The larva is worm-like (maggot)
    • The pupal stage is a resting stage (may have a cocoon)
    • The adult emerges from the pupa
    • Ex: housefly or butterfly
  27. "Modified" Complex metamorphosis
    Female fly retains larvae in her body and they are laid on the host instead of eggs. The larvae quickly pupate after being laid (e.g., Sarcophaga, Oestrus ovis, Melophagus & other hippoboscid flies)
  28. Characteristics of all flies
    • One pair of wings (halteres are vestigial wings; organ of balance)
    • Complex or "modified" complex metamorphosis
Card Set
SGU Parasit 1
SGU Parasitology terms