Principles of parasitism Flashcards
commensalism
reproduce in the host but not a true parasite
parasitism
interferes with host
metabolic dependency of one organism upon a second
fitness characterized by parasite’s ability to:
become established in host
resist environmental stresses
survive host defenses
reproduce and disseminate its progeny
obligatory parasite
cannot complete its lifecycle without spending part or all of its time on or within a host
may use successive series of different hosts
may have free-living stages
facultative parasite
become parasitic when eaten or opportunistically enter host
endoparasite
organism living within host environment
ectoparasite
organism living on host
aberrant parasite
organisms found in locations where they do not normally occur
-do not mature/ facilitate transmission, result in disease state
accidental/ incidental parasite
enter or attach to host species different from ones which normally associated
repeated successful colonization can develop new host association
may not survive on host
pseudoparasite
diagnostic parasite stages that resemble protozoan cysts in feces, blood or urine
hyperparasite
when parasitic organism is host to another parasite species
definitive host
parasite attains reproductive maturity
circulation or passage of progeny capable of colonizing additional host species
intermediate host
larval or intermediate stage parasite must undergo development to become infective for final host
often required developmental stage for completion of life cycle
paratenic host
host used by larvae/ intermediate stage to facilitate transmission to final host
do not undergo development!!
bridges ecological gap between passage of infective stages and successful transmission
reservoir host
maintain a parasite in population at sufficient levels to facilitate its transmission between hosts
may be definitive, intermediate, or paratenic
emphasis on population rather than individual!!
vectors
organisms that facilitate transmission of infective parasite stages between individuals
direct lifecycle
parasites infect host indirectly
stages passed from host in feces/ other tissues
infective to another definitive host
may require period of development to infective stage
indirect lifecycle-obligate
require intervention of intermediate host
stages passed from host in feces/other tissues
infective to intermediate host
requirement for development to infective stage
indirect transmission to definitive host
may involve paratenic host
indirect lifecycle-facultative
indirect transmission to definitive host
optional intervention of intermediate/ paratenic host
stages passed from host in feces/ other tissues
infective to definitive host or optional host
horizontal transmission
parasites colonize susceptible individuals by usual routes
infection across different generations of host population not required
vertical transmission
transmission of parasites from mother to offspring by transplacental or lactogenic routes
trans-generational requirement
high specificity for host
limited number of hosts capable of completing lifecycle
low specificity for host
wide variety of species capable of hosting parasite
typical of intermediate and paratenic host
endemic
normal or usual distribution of parasites in host population or geographical area
epidemic
excess number of parasite cases, far exceeding normal distribution
prevalence
occurrence of parasite in a population defined by time and space
incidence
rate at which new cases are added to new host population defined by time and space
roundworm characteristics
bilaterally symmetrical, cylindrical and elongate
body size ranges
worm-like bodies covered w cuticle
longitudinal muscles only
females larger and males w/ elaborate apparatus
pseudo-coelomate
cuticle fxn
collagenous tissue that resist fluid loss and dehydration
support as flexible exoskeleton
pseudo-coelomate
cross-sectional view “tube w/in tube”
fluid filled body cavity under hydrostatic pressure
complete digestive tract w defined oral opening
female repro tract has varying ovary morphology
