Test 3-10 (Clinical Parasitology)

Question 1

Symbiosis (or mutualism):

Answer 1

Both partners of the association benefit from each other

Question 2

Commensalism

Answer 2

One partner benefits; the other is unaffected

Question 3

Parasitism:

Answer 3

One organism benefits at the expense of the other. All infectious agents causing illness belong to this category.

Question 4

Ectoparasite

Answer 4

live on surface of their host. Usually arthropods (eg. ticks and mites)

Question 5

Endoparasite:

Answer 5

live within the body of the host. Mostly protozoa and helminths.

Question 6

Obligate parasite

Answer 6

• majority fall in this group
• must spend at least part of their life cycle in association with a host. (e.g. Schistosoma (trematode) and Filaria (nematodes))

Question 7

Facultative parasite

Answer 7

are capable of leading both a free and parasitic existence. (e.g. Naegleria (ameba) and Strongyloides (nematode))

Question 8

Trematode

Answer 8

fluke (complex flatworms)

Question 9

Cestode

Answer 9

tapeworm

Question 10

Nematode

Answer 10

roundworm

Question 11

Helminth:

Answer 11

worm

Question 12

Protozoa:

Answer 12

unicellular eukaryotic microbe

Question 13

Vector:

Answer 13

insect that transmits infectious agent from one host to the next

Question 14

how do parasitic diseases occur in non-endemic countries

Answer 14

• Americans traveling to countries where parasites are enderic
• immigration of individuals from endemic countries
• immunocompromised people usually get it first

Question 15

Definitive host definition

Answer 15

a host in which the parasite reaches sexual maturity (adulthood)

Question 16

intermediate host definition

Answer 16

a host that harbors larval or asexual stages of the parasite

Question 17

reservoir host definition

Answer 17

animal (definitive host) that serves to maintain the parasite’s life cycle in the environment.

Question 18

the definitive host is…

Answer 18

the species in which the parasite reproduces sexually

Question 19

parasite reproduction is

Answer 19

sexual and asexual

SOME protoza are ONLY asexuqal though

Question 20

how are protozoa classified

Answer 20

-means of their locomotion

Question 21

trophozoite

Answer 21

term for a protozoa that is metabolically active, motile, and in the parasitic “feeding stage”

Question 22

how are helminths classified

Answer 22

-classified by their body shape: roundworms or flatworms

Question 23

whcih parasite can form cysts and what do the cystsdo?

Answer 23

• protozoa

- produce environmentally resistant cysts that facilitate transmission to their hosts

Question 24

schizogony define

Answer 24

asexual reproduction process (that is different from binary fission) done by sporozoans and some amoebas

Question 25

sporogony

Answer 25

sexual form of reproduction that entails multiple nuclear divisions (meiosis) followed by cytokinesis after zygote formation

Question 26

cuticle

Answer 26

thick membranous coating that covers helminths

Question 27

alimentary canal

Answer 27

basically a digestive system - way to distinguish cestodes and termatode: cestodes do NOT have a digestive system -they abs nutrients directly from host

Question 28

common protals of parasitic entry into host:

Answer 28

-Ingestion: Oral transmission is often due to the consumption of food or water contaminated with parasite eggs (helminths) or cyst (protozoa). Fecal contamination is frequently implicated in the transmission of many parasitic diseases.-Penetration / Inoculation: The larval forms of some helminths (hookworms, schistosomes) found in soil or water have developed the ability to directly penetrate the skin of the host. Many protozoans (malaria, trypanosomes) and a few helminths (filaria) are inoculated into a host by the bite of an insect vector.

Question 29

less common modes of transmission:

Answer 29

• congenital
• direct transmission via sexual contact
• transfusion and transplantation

Question 30

mechanisms of parasitic disease

Answer 30

direct damage caused by the physical presence of the parasite or its products, and immunopathology caused by the host’s response to infection.

Question 31

Mechanical damage to host due to parasite

Answer 31

caused by physical presence of parasite or parasite movement within the host.
Ex: obstruction of the intestine by high worm burdens (Ascaris), blockage of the lymphatics by filarial worms, damaged caused by the migration of helminth larvae through tissues, and lysis of RBC by malaria parasites.

Question 32

Damage caused by parasite products:

Answer 32

-production of products that aid in the establishment and persistence of infections. -Often these products cause severe damage to host tissues and organs, and include hydrolytic enzymes such as proteases, phospolipases, collagenases and hyaluronidases.

Question 33

host’s Immunopathology that causes damage

Answer 33

• formation of granulomas due to parasitic eggs
• molecular mimicry of host proteins = autoimmune diease
• chronic infection= antigen and antibody immune complexes that can get stuck in blood vessels and kidneys

Question 34

immmune responses mounted against parasitic infection: (PROTOZOAL INFECTION)

Answer 34

1. ) neutralizing antibody. e.g. block entry of parasite into host cells
2. ) antibody + complement. e.g. lysis of blood dwelling parasites
3. ) antibody/complement opsonization (plus neutrophils or macrophages) e.g. phagocytosis and clearance of pathogens
4. ) Activated macrophages. e.g. destruction of intracellular protozoa such as Leishmania, Toxoplasma, and Trypanosoma cruzi
5. ) CD8+ cytotoxic T cells. e.g. lysis of parasite infected host cells

Question 35

immmune responses mounted against parasitic infection: (HELMINTH INFECTION)

Answer 35

• difficult for immune system to handle due to size, protective cuticle protects from complement-mediated lysis
• IMMUNE SYSTEM USES IgE and EOSINOPHILS which dump cytotoxic granules on the parasite

Question 36

halmark of helminthic infections:

Answer 36

eosinophilia

Question 37

parasitic evasion of immune response:

Answer 37

• ->Size: The large size of parasitic helminths makes it unlikely that they can be phagocytosed and destroyed by macrophages or neutrophils.
• ->Anatomical location: The fact that many protozoa and helminths reside in the lumen of the gut make it difficult for effector mechanisms of the immune system to reach them.
• ->Intracellular sequestration: parasites hiding from immune system in specific cell types
• ->Formation of cyst: parasites will form cysts that provide an impenetrable barrier to the immune system.
• ->Avoidance of phago-lysosomal destruction: parasites that live inside macrophages and avoid the lysosomal destruction
• ->Antigenic variation: due to genetics and such things
• ->Antigenic masking: coat themselves with host cellular or serum proteins or lipids as a way of masking their own antigens from the immune system.
• ->Immuno-suppression: he exact mechanisms which trigger this suppression are not fully understood, it is thought to involve the production of immuno-suppressive cytokines by macrophages and T-cells in response to parasitic antigens or infection

Question 38

main treatment issue

Answer 38

parasites are eukaryotic and look like the “host”… similar metabolic and cellular processes == the drugs used have toxicity to host

Question 39

Anti-protozoals:

Answer 39

Generally, these compounds target rapidly proliferating, metabolically active cells.

Question 40

Anti-helminthics:

Answer 40

Generally, targeted at non-proliferating adult helminthes. Most affect the neuromuscular system, carbohydrate metabolism, or egg (larvae) production of adult worms.

Question 41

how is differential toxicity achieved:

Answer 41

commonly achieved by preferential uptake of drug by the parasite, metabolic alteration of the drug by the parasite, or differences in the susceptibility of functionally equivalent sites in the parasite and the host.