Virulence and pathogenicity-parasites Flashcards Preview

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Flashcards in Virulence and pathogenicity-parasites Deck (10):

ectoparasite vs. endoparasite


Ectoparasite: lives on host and causes infestations

Endoparasite: lives in host and causes infections


*** Arachnids= ectoparasites

***Helminths= endoparasites


Definitive vs. Intermediate vs. Incidental hosts

Host Specificity: parasites need specific hosts for certain stages of life cycle!


Definitive host: harbors adult stage of parasite.

Intermediate host: harbors larval stage of parasite

Incidental host: unusual host/unnecessary for survival of parasite


Factors influencing parasite virulence (5)

Factors influencing parasite virulence

-type of parasite/host

-host stage

-severity of infection

-duration of infection

-route of exposure


Parasite Pathenogenesis (6)

Parasite Pathenogenesis= pregression of disease

*** these arent really sequential steps, more so just stuff that is all part of the infection/infestation

1. exposure (infective dose)

2. attachment

3. cell and tissue damage

4. loss of nutirents

5. disruption, evasion and inactivation of host defenses


Routes of parasite exposure (6)

Routes of parasite exposure


-Skin/mucosal penetration

-Transplacental (parental)


-Arthropod bite (vector)

-Sexual contact


Infective dose

infective dose= how many/much parasite was host exposed to

Fun Fact: adult helmuths do not multiply in host.  Thus infective dose=severity of disease

protozoa do multiply in host, so severity of infection changes with legnth of exposure.


Parasite attachment (2)

Step 2 of parasite pathenogenesis= attachment

Mechanical attachment- biting, suction disks, attachment organs, ect. (ex. hookworm)

Molecular interaction- some parasites use molecular interactions to target cell.


Cell and tissue damage (2)

Step 3 parasite pathenogenesis= tissue damage

Mechanical tissue damage due to:

  • blockage of internal organs
  • pressure atrophy
  • migration through tissues

Toxic parasite products damage tissue with:

  •  destructive enzymes
  • endotoxins
  • toxic secretions


Loss of nutrients (3)

Step 4ish parasite pathenogenesis= loss of nutrients

Nutrient loss can be due to:

1. parasite competition with host for nutrients

2. interference with host nutrient absorption

3. direct nutrient loss- hookworm causes iron loss


Concomitant vs. Premonition Immunity

Aquired immunity

Concomitant Immunity: immunity defends against all stages of a parasite, even if parasite is eradicated from host. 


Premonition Immunity: immunity develeoped to current parasites.  when parasited are gone, immunity is lost.