protozoan and helminth parasite Flashcards
what is parasitism
the parasite benefits at the expense of the host
what are obligate parasites
spend at least part of their life cycle in parasitic relationship
what are facultative parasites
free living but can become parasitic if enter a suitable host
what is a definitive host
where the parasite reaches sexual maturity
what is a intermediate host
host required for parasite development but no sexual development takes place
what is an incidental host
a host that can be infected but does not play a role in lifecycle
what is a paratenic host
no development takes place but parasite remains alive and infective to another host
what are helminths
parasitic worms
what are the 3 main groups of helminths
nematodes
cestodes
trematodes
what are nematodes
roundworms
what are cestodes
tapeworms
what are trematodes
flukes
what is the most common helminthic infection
whipworm
how does whipworm infect a host
eggs ingested from environment and sexual reproduction occurs in mammalian host
how do whipworms act once in host
larvae emerge in duodenum + females and males mate
what are the effects of the helminth (nematode) trichuris dysentery syndrome
cause diarrhea, intestinal bleeding, iron deficiency and rectal prolapse
what can filarial worms cause
can cause river blindness
what is taeniasis
adult worms found in the gut
how may cysticercrosis develop
after indigestion of eggs from environment and become larvae to penetrate intestinal wall
How can infecting hosts be a challenge for protozoal parasites
May involve migration and parasite motility to transport around host
What challenges may protozoal parasites encounter
Undergoing transmission
Gaining nutrients - having to adapt to different environments
Avoid being killed by host
Maintain balance between proliferation and forming long term infection
What is a sporozoite
Injected into the human host when mosquito feeds
What is a gametocyte
Sexual stages that form in the human
What is an Ookinete
Formed from macrogametocyte and microgametocyte
How is toxoplasmosis caused
By opportunistic infections, blurred vision caused by severe inflammation of retina
How can humans be infected by toxoplasma gondii infection
Contamination by cat faeces
Eating infected meat
How is the African trypanosomiasis transmitted
By the tsetse fly (definitive host)
How do African trypanosomiasis replicate
T. Brucei proliferates extracellularly in the host bloodstream and moves into CNS later into the infection
How can parasites evade host immune response
Hide in host cells
Live free in the bloodstream
Live in protected sites (e.g gut, brain)
What are the advantages of a parasite living within a red blood cell
Gain nutrients from host cell
Shielded from host immune system
Host cells (erythrocytes) are readily available and are accessible to mosquito vector
Transmission is v efficient
What are the disadvantages of a parasite living within a red blood cell
Remodelling of cell membrane by parasite causes inc. cell rigidity
Parasite must convert terminally-differentiated erythrocytes into cells with nutrient uptake system
Infected erythrocytes may be detected and removed by spleen
What do apicomplexan parasites use to invade host cells
Gliding motility
Where is gliding motility used during parasite invasion
Used by motile stages of lifecycle to migrate to host cell and propel themselves into host cell
What must intracellular parasites avoid to escape immune detection
Evade host cell killing mechanism
Prevent host cell apoptosis
How is pfEMP1 encoded
Encoded by around 60 members of the var gene family
How does PfEMP1 play a role in a parasite evading immune detection
A role in antigenic variation encoding var genes to allow about 60 different versions per individual parasite genome
What coat can shield parasites
Variant surface glycoprotein coat (VSG)
What are characteristics of the N-terminal of the VSG
Antigenic diversity
Highly variable sequence
Forms similar structure
What are characteristics of the C-terminal of the VSG
Surface packing
Conserved region
Anchored into plasma membrane
How many VSG can be activated at a time
One one promoter is active at a time
What are the 4 mechanisms of switching between different VSGs
Gene conversion
Segmental gene conversion
Telomere exchange
Transcriptional switch
How does a parasite infect a new host
Parasite must stop proliferating and differentiate into transmission-competent form
What does a slender form of a parasite allow for
Proliferation
What does a stumpy form of a parasite allow for
Transmission
