Virulence and pathogenicity-parasites

Question 1

ectoparasite vs. endoparasite

Answer 1

Ectoparasite: lives on host and causes infestations

Endoparasite: lives in host and causes infections

*** Arachnids= ectoparasites

***Helminths= endoparasites

Question 2

Definitive vs. Intermediate vs. Incidental hosts

Answer 2

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

Question 3

Factors influencing parasite virulence (5)

Answer 3

Factors influencing parasite virulence

• type of parasite/host
• host stage
• severity of infection
• duration of infection
• route of exposure

Question 4

Parasite Pathenogenesis (6)

Answer 4

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

Question 5

Routes of parasite exposure (6)

Answer 5

Routes of parasite exposure

• Ingestion
• Skin/mucosal penetration
• Transplacental (parental)
• Transmammary(milk)
• Arthropod bite (vector)
• Sexual contact

Question 6

Infective dose

Answer 6

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.

Question 7

Parasite attachment (2)

Answer 7

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.

Question 8

Cell and tissue damage (2)

Answer 8

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

Question 9

Loss of nutrients (3)

Answer 9

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

Question 10

Concomitant vs. Premonition Immunity

Answer 10

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.