PARASITOLOGY Flashcards
Symbiosis
living together of phylogenetically different organisms
Mutualism
beneficial to both organisms
Commensalism
beneficial to one organism, neutral to the other
Parasitism
beneficial to one organism, harmful to the other
Definitive Host
harbors the adult or sexual stage of a parasite
Examples of Definitive Host
- Cat - DH of T. gondii
- Mosquito (Female anopheles) - DH of Plasmodium spp.
Intermediate Host
Harbors the larval or asexual stage of a parasite
Examples of Intermediate Host
- Mosquitoes - IH of Filarial worms
- Snail - IH of ALL trematodes (schistosomes and hermaphrodites)
- Man - IH (accidental) host of Echinococcus spp. (Dog is DH)
Paratenic Host
Harbors a parasite that does not develop but remains alive and if infective to the next host. Carries or bridges the parasite to the next host.
Examples of Paratenic Host
- Large fish - PH of D. Latum
- Snake, bird - PH of G. spinigerum
Obligate Parasite
Depends entirely upon its host for existence. MOST PARASITES ARE OBLIGATE PARASITES.
Reservoir
Allows the parasite’s life cycle to continue and serves as a source of human infection
Example of Reservoir
- Pig - RH of B. coli (also considered zoonotic)
Facultative Parasite
Capable of parasitic and free-living existence
Examples of Facultative Parasite
- S. stercoralis
- FLAs (Naegleria, Acanthamoeba spp.)
Classification of parasite according to number of host required
Transitory, Permanent, Periodic
Transitory parasite
Larval stage is passed in a host while the adult is free living in only 1 host
Example of transitory parasite
S. stercoralis (INDIRECT LIFE CYCLE ONLY)
Permanent parasite
Completes its life cycle in 1 host for all the life stages
Example of permanent parasite
H. nana - the only cestode that is capable of this. Also called monoxenous or homoxenous (DIRECT LIFE CYCLE ONLY)
Periodic parasite
Requires 2 or more hosts (heteroxenous) for the larval and adult stages
Example of periodic parasite
Trematodes and cestodes (Except H. nana)
Zoonotic parasite
Primarily infects animals and may be acquired by man and causes infection in man
Examples of zoonotic parasite
- B. coli
- D. immitis
- Agents of larva migrans
Accidental parasite
Occurs in an unusual host
Examples of accidental parasites
- Echinococcus
- Agents of larva migrans (maturation is arrested at larval stage - meaning life cycle will not continue)
Erratic parasite
Occurs in an unusual organ or habitat
Example of erratic parasite
- A. lumbricoides - can cause ectopic ascariasis (it is supposed to be in the small intestine)
Spurious or coprozoic parasites
Passes through the intestinal tract without causing any disturbance (DON’T CAUSE INFECTION)
Examples of spurious or coprozoic parasite
- F. hepatica unembryonated eggs - not infectious, metacercaria is the infective stage in man
- C. hepatica unembryonated eggs
Endoparasite
Lives inside the body of a host (MOST PARASITES ARE ENDOPARASITES)
What is it called when an endoparasite invades a host?
INFECTION
Ectoparasite
Lives on body surfaces
What is it called when an endoparasite invades a host?
INFESTATION
Examples of ectoparasites
- Lice (Pediculus humanus capitis, P. h. humanus, Phthirus pubis)
- Itch mite (Sarcoptes scabei)
Intermittent parasites
Visits the host only during feeding time
Examples of intermittent parasite
- Bed bug
- Mosquito
- Flea
- Tick
- Biting fly
Arthropods are considered as?
Ectoparasite, Intermittent parasite, vectors
Biologic Vector
transmits a parasite only after the latter has completed part of its development; may also serve as a host
Mechanical or Phoretic
not essential in the parasite’s life cycle and is responsible only for transporting the parasite via appendages or external surfaces