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
what ectoparasites serves as parasites and vectors?
arthropod ectoparasites
what are the two main life cycles for ectoparasites?
-holometabolous (complete) metamorphosis
-hemimetabolous (incomplette, simple) metamorphosis
Describe the holometabolous (complete) metamorphosis
egg -> larva -> pupa -> adult
Describe the hemimetabolous (incomplete, simple) metamorphosis
egg -> larva -> nymph -> adult
egg -> nymph -> adult
what type of metamorphosis has larval that is morphological different from the adult?
holometabolous (complete) metamorphosis
what type of metamorphosis has larval that is morphological similar to the adult?
hemimetabolous (incomplete, simple) metamorphosis
what type of metamorphosis do fleas and dipterans have?
holometabolous
what type of metamorphosis do tick, mites, and lice have?
hemimetabolous
what type of metamorphosis is this?
hemimetabolous
what type of metamorphosis is this?
holometabolous
what is the mode of transmission of Dirofilaria immitis
vectored by moquitoes
what is the infective stage of Dirofilaria immitis
third-stage larva, L3
How does Dirofilaria immitis get from the mosquito into the host?
L3 migrates through mosquito bite wound
What is the predilection site of the adult for Dirofilaria immitis?
pulmonary arteries, right ventricle
what is the route to the predilection site for Dirofilaria immitis?
venous circulation (from subcutis and abdominal/thoracic muscles)
what is the mode of exit of Dirofilaria immitis?
blood ingested by mosquito
what is the exiting/diagnostic stage of Dirofilaria immitis?
Microfilaria in blood
where is A. suum located in the pig throughout its life?
larva in lung tissue
larva in large intestinal wall and liver (migrate up to lungs)
larva in small intestine (prepatent week 6-8)
what pathogen might have caused this?
A. suum
Define prepatent period
time between infection of a definitive host and the appearance of stage exiting host
how is the prepatent period controlled with A. suum?
control through deworming
what is this a technique for?
collection of soil or vegetation samples to locate the different stages of the parasite external to host
what can locating the different stages of the parasite external to the host help with?
epidemiology, environmental assessment, and control
what environmental conditions that contribute to promoting development/survival of stage?
temperature, humidity, shade, etc.
How does knowing the time required for development of stages and longevity of stages help with for parasite external to the host?
epidemiology, control
ex. knowing what egg looks like that is infective vs non-infective
what parasite mostly develops and reproduces in only 1 host species?
lice
what parasite mostly develops and reproduces in more than 1 host species but are restricted to a genus or family of hosts?
most coccidia
what is a parasite that develops and reproduces in more than 1 family or order of hosts?
Trichonstrongylus axei
what are the definitive and intermediate hosts for Toxoplasma gondii - toxoplasmosis?
definitive hosts - felids
intermediate hosts - mammals and birds
what are the definitive and intermediate hosts for Schistosoma japonicum - schistosomiasis?
definitive hosts - rodents, carnivora, ungulates, primates, and other mammals
intermediate hosts - snails in genus Oncomelania
what are the definitive and intermediate hosts for Plasmodium reichenowi - malaria?
definitive hosts - mosquitoes in genus Anopheles
intermediate hosts - chimpanzees
what are the two main lifecycles for endoparasites?
direct and indirect
