Lecture 6: Virulence and Pathogenicity of Parasites Flashcards
Three groups of eukaryotic organisms that afflict health and well-being
- Protozoa
- Helminths
- Arthropods
Ectoparasite
- Lives on host
- Causes infestations
Endoparasite
- Lives in host
- Causes infections
Definitive host
harbors adult (sexual) stage of parasite
Intermediate host
harbors larval stage (asexual) of the parasite
Incidental host
an unusual host, unnecessary for the maintenance of the parasite in nature
Parasites have specificity for particular definitive and intermediate hosts, meaning
often parasitic life cycles can only be completed in a particular host
In different hosts, disease manifestations may
differ
6 common routes of parasite entry
- Ingestion
- Skin/mucosal
- Transplacental
- Transmammary
- Anthropod bite
- Sexual contact
Protozoa multiply where?
in hosts
Do helminthes multiply in definitive host?
-Not in definitive host
Severity of Helminth disease is proportional to
worm load introduced in the host
Two methods of attachment
- Mechanical or biting mouthparts
- Molecular interaction
Three types of mechanical tissue damage
- Blockage of internal organs
- Pressure atrophy
- Migration through tissue
Three types of toxic parasite products
- Destructive enzymes
- Endotoxins
- Toxic secretions
Three ways to lose nutrients
- Competition with hosts
- Interference with nutrient absorption
- Nutrient loss
Natural or innate immunity
A defense mechanism that does not depend upon prior exposure to the invader
Three types of natural or innate immunities
- Cytokines/cytokine receptors
- Antimicrobial molecules and pattern recognition receptors
- Cellular defense/phagocytosis
Acquired immunity
Conferred by a host’s specific immunity response developed as a result of previous parasitic infection
Two types of acquired immunity
- Premunition
- Concomitant immunity
Premunition
Resistance to superinfection by presence of parasites in check by host immunity-malaria, toxoplasmosis
Concomitant immunity
a parasite elicits a protection against reinfection, but the parasite itself remains in the host, unaffected by the immune response
