Lecture 46 - Intro to Protozoa Flashcards
T/F: all protozoa are free-living
FALSE - some are parasitic
how do protozoa reproduce
- binary fission
- budding
- multiple fission
- sexual
symbionts
2 organisms that live in close association with each other
parasitic protozoa life-cycle
infection of hosts and reproduction
parasite
a symbiont that is dependent on host organisms
parasitic protozoa pathology
mechanisms that cause disease in the host
direct life cycle
requires single host species
indirect life cycle
requires an intermediate host species
facultative indirect life cycle
can use an intermediate host but not required
transmission to new hosts
route, infectious immediately or need to develop
stages of protozoa
- cysts (resistant)
- trophozoite (growing)
- tachyzoite (fast-growing)
T/F: high host specificity is important for zoonosis
FALSE - low host specificity
definitive host
supports protozoa asexual and sexual reproduction
intermediate host
supports asexual multiplication
indirect - through the food chain
REQUIRED
facultative intermediate (paratenic) hosts
supports asexual multiplication
indirect - through the food chain
NOT required to complete a life cycle
accidental/aberrant/dead-end host
supports asexual multiplication
won’t complete its lifecycle
giardia
direct or indirect?
immediately infectious?
stages?
direct
yes - immediately infectious
cysts and trophozoite
toxoplasma
direct or indirect?
immediately infectious?
different hosts?
both direct and indirect
no - not immediately infectious
definitive (cat)
facultative intermediate (opossum)
accidental host (human)
what are 4 reasons we need to know life cycles
- control disease
- diagnose
- educate
- treatment
what are the 4 main mechanisms of protozoa pathogenesis
- direct
- indirect
- immunomodulation
- excretion of toxins
describe direct pathogenesis
asexual reproduction inside the host cells causing cellular and organ trauma
describe indirect pathogenesis
proliferation on the host cell surface
impairment, damage or apoptosis
describe immunomodulation pathogenesis
- autoimmune reactions (generate autoantibodies against self)
- suppression (alters immune response for longevity)
describe the excretion of toxin pathogenesis
secrete toxic substances
cause inflammation and host cell apoptosis
what is the best way to describe an indirect life-cycle
when a parasite’s life cycle must include an intermediate host species
