RA#3 Flashcards
One organism benefits at the expense of the other. All infectious agents causing illness belong to this category
parasitism
Parasitic disease are infections that are usually caused by which organisms (3)?
1) helminths (worms)
2) protozoa
3) arthropods (insects, ticks, etc.)
These parasites live on surface of their host, usually arthropods
ectoparasite
These parasites live within the body of the host, mostly protozoa and helminths
endoparasite
These parasites must spend at least part of their life cycle in association with a host
obligate (majority)
These parasites are capable of leading both a free and parasitic existence
facultative
insect that transmits infectious agent from one host to the next
vector
unicellular eukaryotic microbe
protozoa
worm
helminth
roundworm
nematode
tapeworm
cestode
fluke (complex flatworms)
trematode
True or False. Parasitic infections currently account for greater morbidity and mortality than any other class of infectious agents
True
A host in which the parasite reaches sexual maturity (adulthood)
definitive host
A host that harbors larval or asexual stages of the parasite
intermediate host
Animal (definite host) that serves to maintain the parasite’s life cycle in the environment
reservoir
True or False. The more complicated an organism’s life cycle, the less likely chance of survival it has.
True, but many of these organisms usually offset this hazard by developing highly productive reproductive capabilities or some form of efficient multiplication during one of its stages of development
What are the four main classes of protozoa based on locomotion?
1) ameba –> pseudopodia
2) flagellates –> flagella
3) sporozoa –> gliding
4) ciliates –> cilia
Ameba, flagellates, and ciliates generally reproduce themselves asexually via …
binary fission
Multiple intracellular nuclear divisions (mitosis) that precede cytoplasmic division characterize ….
schizogony
Sexual form of reproduction that entails multiple nuclear divisions (meiosis) followed by cytokinesis after zygote formation
sporogony
What’s the function of a cyst?
protects the organism from the environment during passage from host to host
Multicellular organisms often having an elongated appearance
helminths
Helminths often have a thick membranous coating called ____
cuticle
Which type of helminths are segmented and lack digestive system?
cestodes
Which helminths are hermaphrodites?
cestodes and trematodes
Which helminths are non-segmented and have a leaf-shaped appearance?
trematodes
Which helminths have separate sexes?
nematodes
How many hosts do nematodes usually have?
one
How many hosts do cestodes and trematodes have?
one or more intermediate host (more complex life cycles than nematodes)
Transmission of a parasitic disease involves which three factors?
1) source of infection
2) mode of transmission
3) presence of susceptible host
What is the primary source of most parasitic diseases?
humans, animals frequently act as reservoirs or intermediate hosts
What are the different modes of transmission?
1) ingestion
2) penetration/inoculation
3) direct transmission
4) congenital transmission
5) transfusion and transplantation
Sexual contact is involved with which mode of transmission?
direct transmission
Which mode of transmission involves mother to infant transmission?
congenital transmission
Which mode of transmission involves blood or tissue dwelling parasite such as malaria?
transfusion and transplantation
Which mode of transmission involves larval forms of some helminths found in soil or water that have developed the ability to directly penetrate the skin of the host?
penetration/incoculation
Which modes of transmission involves consumption of food or water contaminated with parasite eggs or cyst?
ingestion
What are some mechanisms by which parasites produce pathology?
1) mechanical damage
2) damage caused by parasite products
3) immunopathology
Obstruction of the intestine by high worm burdens or blockage of the lymphatics by filarial worms are examples of which pathologic mechanism?
mechanical damage
What does it mean by immunopathology?
response of the host to parasitic infection can often result in or contribute to pathology
What are some examples of immunopathology?
1) formation of granulomas
2) autoimmune response triggered by parasite antigens that have structural similarity to host proteins
3) formation of circulating immune complexes leading to development of vasculitis or nephritis
4) previous exposure can result in hypersensitivity leading to anaphylactic shock, bronchospasm, or local inflammation
What are some immune response to protozoal infections (5)?
1) neutralizing Ab
2) Ab + complement
3) opsonization
4) activated macrophages
5) CD8+ (cytotoxic T cells)
What are some immune response to helminthic infections?
IgE and esosinophils
Eosinophilia is a hallmark of which type of infections?
helminthic infections
What are some ways parasites evade immune defenses?
1) size
2) anatomical location
3) intracellular sequestration
4) formation of cyst
5) avoidance of phago-lysosomal destruction
6) antigenic variation
7) antigenic masking
8) immuno-suppresion
What are some difficulties in treating parasites?
parasitic cells are eukaryotic cells and they carry out much of the same cellular and metabolic process as we do. Many drugs often exhibit a fair amount of toxicity to the host
Which drug treatment targets rapidly proliferating, metabolically active cells?
anti-protozoals
Anti-helminthics generally target what?
non-proliferating adult helminthes. Most affect neuromuscular sys, carb metabolism or egg production of adult worms
