Life Cycles Flashcards
what can knowing the life cycle help with?
-diagnose disease & ID parasite
-predict what pathogenic changes may occur
-optimize treatment to improve control
-develop environmental control programs
-reduce cross-species (including zoonotic) infections
Define definitive (primary, principal, final) host
host in which the adult or sexually reproductive, stages of the parasite occur
Define intermediate (secondary) host
host required for parasite development but in which the parasite does not become sexually mature
Define paratenic (transport) host
host in which parasite does not undergo any required development but in which it remains alive & infective to another host
what is included in a direct life cycle?
definitive host and no intermediate host
define monoxenous parasite
parasites with direct life cycles
what types of parasites are monoxenous?
nematodes and protozoa
when might be the infective stage in a direct life cycle?
resting stage or active stage
what are the modes of transmission of a resting stage in the direct life cycle?
ingestion
what are the modes of transmission of the active stage in the direct life cycle?
ingestion, penetration of skin, direct contact
what are two parasites with direct life cycles?
Ascaris suum and Hyastrongylus rubidus
what is included in a indirect life cycle?
requires an intermediate host
what type of life cycles do heteroxenous parasites have?
indirect life cycle
what are some heteroxenous parasites?
trematodes, most tapeworms, and many parasitic nematodes, and protozoa
when might be the infective stage in an indirect life cycle?
resting stage
active stage
what are the modes of transmission in the resting stage of the indirect life cycle?
transmission via ingestion
what are the modes of transmission in the active stage of the indirect life cycle?
penetration of skin, via vector
what are two parasites with indirect lifecycles?
Spirurid nematode
Dirofilaria immitis
Are paratenic hosts required for completion of parasites life cycle?
Not required, facilitates transmission to definitive host
what is the paratenic host for Stephanurus dentatus (swine kidney worm)?
earthworm - carries infective larvae
what are the 4 modes of transmission with Stephanurus dentatus?
-ingestion of free infective larvae
-ingestion of earthworm (paratenic host) carrying infective larvae
-penetration of skin by infective larvae
-transplacental transmission