Clinical Parasitology- RA3 Flashcards
Parasitism
One organism benefits at the expense of another
Symbiosis/ Mutualism
Both partners benefit from each other
Commensalism
One partner benefits, the other is unaffected
Ectoparasite
Lives on surface of the host (e.g. arthropods)
Endoparasite
Lives within the host (e.g. protozoa & helminths)
Obligate parasite
Must spend at least part of the lifecycle associated with host
Faculative parasite
Capable of living a free & parasitic existence
Vector
Insect that transmits infectious agent
Protozoa
Uunicellular eukaryotic microbe
Helminth
Worm
Namatode
Roundworm
Cestode
Tapeworm
Trematode
Fluke (flatworm)
Describe the prevalence of parasitic diseases worldwide & especially in developing/under-developed countries.
“Parasitic infections currently account for greater morbidity & mortality than any other class of infectious agent in developing or under-developed countries.”
List the characteristics of protozoa.
- Single celled eukaryotes
- Nucleated
- Contain organelles
- Many encyst themselves
List the characteristics of helminths.
- Multicellular
- Elongated appearance
- Covered by a thick membranous coating called a cuticle
How are protozoa classified?
Based on locomotion
What are the four classes of protozoa?
Ameba
Flagellates
Sporozoa
Ciliates
Ameba
Pseudopodia
Flagellates
Flagella
Sporozoa
Gliding
Ciliates
Cilia
What is special about the reproductive mechanism of the sporozoa?
Reproduction by schizogony
What is Schizogony?
Multiple intracellular nuclear divisions prior to cytoplasmic divison
How are Helminths classified?
Roundworm vs. Flatworm
What group belongs to the roundworms?
Namatodes
What groups belong to the flatworms?
Cestodes & Trematodes
What is the difference between Cestodes & Trematodes?
Cestodes= Tapeworm that is segmented & lacks a digestive tract
Trematode= non-segmented “Fluke”
List the modes of parasitic transmission.
- Ingestion
- Direct penetration of skin
- Inoculation by vectors
- Congenital transmission
- Transmission by transfusion or transplantation
What are the mechanisms of parasitic disease?
- Mechanical damage
- Damage caused by parasitic products
- Damage caused by the immune response to the parasite
How does the immune response to protozoa differ from the response to helminths?
Protozoa= typical response similar to what would be seen against virus or bacteria
Helminths= IgE & eosinophil dominated
How do parasites evade the immune system?
- Size = often too large to be phagocytosed
- Anatomical Location= residence in the gut makes it difficult for immune system to reach them
- Intracellular sequestration
- Formation of a cyst
- Avoidance of phago-lysosomal destruction
- Antigenic variation
- Antigenic masking
- Immunosuppression
What is the major challenge to chemotherapeutic & immunological interventions to parasitic disease?
- Parasitic organisms are eukaryotic cells & are very similar to human cells
- Thus, treatment often results in toxicity to the host
- Differential toxicity is achieved by using drugs that are metabolically altered only by the parasite
What are the two major drug groups used in treating parasitic infections?
- Anti-protozoals= target rapidly proliferating, metabolically active cells
- Anti-helminths= Affect the neuromuscular system, carbohydrate metabolism, or egg production of adult worms
