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Parasitology > Lecture 2: Life Cycles > Flashcards

Lecture 2: Life Cycles Flashcards

1
Q

definitive, intermediate and paratenic hosts apply to: endoparasites or ectoparasites?

A

endoparasites

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2
Q

definitive host

A

primary, principal final host
host in which the adult, or sexually reproductive, stages of parasite occur

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3
Q

intermediate host

A

host required for parasite development but in which parasite doesn’t become sexually mature

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4
Q

paratenic/transport host

A

parasite does not undergo any required development but it remains alive and infective to another host (could be the definitive host or a different species that serves as paratenic host)

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5
Q

what happens when definitive host ingests the paratenic host

A

parasite completes its development

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6
Q

do direct life cycles include intermediate hosts

A

no

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7
Q

does direct life cycle include definitive host

A

yes

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8
Q

Monoxenous parasites

A

Parasites with direct life cycles

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9
Q

Direct life cycle Infective stage: Resting vs active stage

A

Resting = mode of transmission is ingestion
Active = ingestion, penetration of skin, sexual contact

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10
Q

Direct life cycle: definition

A

Life cycle that includes a definitive host but no intermediate host

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11
Q

Indirect life cycle: definition

A

Requires an intermediate host

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12
Q

Heteroxenous parasites

A

Indirect life cycle with intermediate host

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13
Q

Examples of monoxenous parasites (2)

A

Nematodes and Protozoa

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14
Q

Examples of heteroxenous parasites (4)

A

Trematodes
Most tapeworms
Nematodes
Protozoa

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15
Q

Indirect life cycle infective stage: resting vs active stage transmission mode

A

Resting = ingestion
Active = penetration of skin, vector

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16
Q

Examples of spirurid nematodes found in pigs’ stomachs (2)

A

Ascarops strongylina
Physocephalus sexalatus

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17
Q

Where can you find/identify ascaris sum eggs

A

Swine feces

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18
Q

Pathogenic changes: ascarids

A

Larvae migrate through liver and lungs
Damage to lungs
Secondary bacterial infection risk

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19
Q

How to treat ascaris (swine)

A

Deworm confined sows 1 week before farrowing
If moved out of confinement, deworm every day for first 30 days then in 8 week intervals

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20
Q

Environmental control: ascaris

A

Eggs very resistant to environmental degradation and disinfectants
Can destroy eggs by intensive steam cleaning, flaming, prolonged exposure to full sunlight

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21
Q

Ascaris cross species infections

A

A. Suum (pigs) and A. Lumbricoides (humans)
People who work with pigs get swine ascarids and vice versa

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22
Q

Direct life cycle + paratenic host: definition

A

Paratenic NOT required for completion of parasite’s life cycle
But it does facilitate transmission to definitive host

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23
Q

Stephanurus dentatus is an example of parasite with what kind of life cycle

A

Direct with paratenic host

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24
Q

Stephanurus dentatus: 4 modes of transmission

A

Ingestion of free infective larvae
Ingestion of earthworm/paratenic host carrying infective larvae
Penetration of skin of pig by infective larvae
Transplacental transmission of pig by infective larvae

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25
Most infections with Stephanurus dentatus occur by which transmission method
Ingestion of free infective larvae
26
Stephanurus dentatus: how paratenic host contributes to life cycle
Earthworm not required for host to complete life cycle Earthworm ingest Stephanurus larvae and don’t develop further but are instead waiting for pig to eat earthworm
27
Stephanurus dentatus is what kind of parasite (hint: general classification and life cycle)
Monoxenous nematode
28
Example of paratenic host with heteroxenous parasite
Spirometra mansonoides tapeworm
29
Arthropod ectoparasites serve as (2)
Parasites Vectors
30
2 main life cycles of arthropod ectoparasites (2 general names)
Holometabolous/complete metamorphosis Hemimetabolous/incomplete metamorphosis
31
Holometabolous metamorphosis: process, does morphology differ between larval and adult stages?, what stage molts during growth
Egg —> larvae —> pupa —> adult Morphology of larval stage very different from adult Larval stage molts several times during growth Variation in what stage is parasitic
32
Hemimetabolous metamorphosis: 2 possible processes with examples of general ectoparasites
Egg —> larva —> nymph —> adults (ticks, mites) Egg —> nymph —> adult (lice)
33
Hemimetabolous metamorphosis: does morphology of larval stage differ from adult?, what stage molts during growth, variations that exist
Larval/nymphal morphology similar to adult Nymphal stages molt during growth Eggs can be laid on host or in environment, all active stages can be found on 1 host or different stages can be found on different hosts
34
6 modes of transmission for parasites
Ingestion Penetration of skin/mucous membranes Vector Direct contact/sexual Transplacental Transmammary
35
Possible infective stages (7)
Egg Larval worm Protozoan cyst Protozoan trophozoite Arthropod larvae Nymph Adult
36
The stage exiting the host is called
Diagnostic stage
37
Predilection site definition
Preferred site of adult or sexually/asexually reproducing stage within or on host which is characteristic for particular parasite species
38
Dirofilaria immintis: generic name
Canine heart worm
39
Dirofilaria immitus: mode of transmission, infective stage, predilection site of adult, route to predilection site, mode of exit, exiting/diagnostic stage
Vectored by mosquitos L3 —> deposited on skin then migrates through mosquito bite wound and into dog Pulmonary arteries, right ventricle Venous circulation from abdominal/thoracic muscles Blood ingested by mosquito Microfilaria in blood
40
Ascaris suum: locations and timing/duration of different stages, when are first eggs passed in feces, how long do adults live
Infective eggs ingested —> larvae hatch and migrate from small intestine —> liver (within 8-18 hrs of infection) —> lungs (4-6 days after infection) —> bronchial tree —> trachea —> pharynx —> small intestine (8-10 days after infection) —-> mature and mate in SI First eggs passed 6-8 weeks after infection Adults live 6-9 months
41
Ascaris suum: pathology
Larval migration through liver = hemorrhage, fibrosis, lymphocyte infiltration —> white spots(milk spots) Larval migration through lungs = hemorrhagic lesion, eosinophil infiltration, severe/repeated infections cause edema/pneumonia/emphysema/death Maturing and adult worms in small intestine = inflammation, diarrhea, rob host of nutrients, obstruction possible
42
Prepatent period definition
Time between infection of definitive host and appearance of stage exiting host
43
Ascaris suum: diagnosis
**prepatent period Clinical signs = chronic paroxysmal cough, abdominal breathing, weight loss Postmortem = liver/lung lesion, larval worms in lung tissue, large immature worms in SI Patent infection = eggs/adults in feces
44
Main pathologic events occur during which stage of infection
Prepatent
45
Ascaris suum: treatment (3)
Pyrantel and fenbendazole = kill migrating larvae During respiratory phase of infection Supportive care + tx for secondary infections
46
How long is prepatent period for ascaris suum
6-8 weeks
47
How to control prepatent period of ascaris suum
Deworming!!
48
Locations of different stages external to host (6)
Soil Water Vegetation Fomites Intermediate host Paratenic host
49
Ascaricosis of swine: epidemiology
Infective eggs are sticky/resistant/long lived and found in contained water, soil, water, vegetation, walls, floors, fomites Infective eggs transported by pigs, people, other mammals, insects, worms
50
What information is needed for parasite control (environment)
Distribution and numbers of infective stages
51
Environmental assessment: ascaris suum eggs
Soil/vegetation samples from pastures Soil samples from dry lots Analyzed for eggs
52
Control of ascaris suum (what is the name of this technique)
Cleanliness, deworm and wash sows before farrowing “Dose and move” —> deworm before moving to clean areas, use pasture rotation
53
Environmental conditions that promote development/survival of stages external to host (3)
Temperature Humidity Shade/exposure to UV light
54
Development/survival of what 4 external stages are affected by environmental conditions
Eggs = helminths, ectoparasites Helminth larvae Larvae/nymphs of ectoparasites Protozoan cysts
55
Transmission hiatus
When environmental conditions are enough to inhibit growth/survival of parasites so anthelmintic tx not necessary
56
Ascaris suum eggs: winter vs spring (and why this is important for prevention)
Winter = eggs accumulate but don’t develop Spring = eggs develop and become infective Move pigs to safe pasture before spring rise in temp
57
Environmental conditions that promote and deter ascaris suum egg infection
25 degrees C, moist, shade = become infective in 2-4 weeks Below 15 degrees C= will not develop Low humidity/heat/direct sunlight = reduce survival Resist freezing Remain viable for 10 years
58
Ascaris suum: control strategies to reduce infection rates (2)
Daily removal of feces from and thorough cleaning of indoor facilities, outdoors feeders/waterers Weaning and removing pigs from infected sows before the eggs that are shed from sows become infective
59
When do ascaris suum eggs become infective
2 weeks
60
Geomydoecus heaneyi: generic name, host
Chewing louse 1 species of gopher = Llano pocket gopher
61
Eimeria onychomysis: type of parasite, host genus
Coccidian 3 known species of grasshopper mice = Onychomys genus
62
Trichostrongylus axei: type of parasite, different hosts
Stomach hair worm Adults in abomasum of ruminants + stomach of horses/swine/humans/rabbits
63
Disease caused by toxoplasma gondii
Toxoplasmosis
64
Toxoplasma gondii: definitive hosts, intermediate hosts
Definitive = sexual stages restricted to hosts in family Felidae (only felids can shed oocysts produced via sexual reproduction) Intermediate = mammals and birds
65
Disease caused by schistosoma japonicum
Schistosomiasis
66
Schistosoma japonicum: definitive and intermediate hosts
Definitive = rodents, Carnivora, ungulates, primates Intermediate = snails in genus Oncomelania
67
Disease caused by plasmodium reichenowi
Malaria
68
Plasmodium reichenowi: definitive and intermediate hosts
Definitive = mosquitos in genus Anopheles Intermediate = chimpanzees

Parasitology (10 decks)

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