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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
Q

Most infections with Stephanurus dentatus occur by which transmission method

A

Ingestion of free infective larvae

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26
Q

Stephanurus dentatus: how paratenic host contributes to life cycle

A

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

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27
Q

Stephanurus dentatus is what kind of parasite (hint: general classification and life cycle)

A

Monoxenous nematode

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28
Q

Example of paratenic host with heteroxenous parasite

A

Spirometra mansonoides tapeworm

29
Q

Arthropod ectoparasites serve as (2)

A

Parasites
Vectors

30
Q

2 main life cycles of arthropod ectoparasites (2 general names)

A

Holometabolous/complete metamorphosis
Hemimetabolous/incomplete metamorphosis

31
Q

Holometabolous metamorphosis: process, does morphology differ between larval and adult stages?, what stage molts during growth

A

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
Q

Hemimetabolous metamorphosis: 2 possible processes with examples of general ectoparasites

A

Egg —> larva —> nymph —> adults (ticks, mites)
Egg —> nymph —> adult (lice)

33
Q

Hemimetabolous metamorphosis: does morphology of larval stage differ from adult?, what stage molts during growth, variations that exist

A

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
Q

6 modes of transmission for parasites

A

Ingestion
Penetration of skin/mucous membranes
Vector
Direct contact/sexual
Transplacental
Transmammary

35
Q

Possible infective stages (7)

A

Egg
Larval worm
Protozoan cyst
Protozoan trophozoite
Arthropod larvae
Nymph
Adult

36
Q

The stage exiting the host is called

A

Diagnostic stage

37
Q

Predilection site definition

A

Preferred site of adult or sexually/asexually reproducing stage within or on host which is characteristic for particular parasite species

38
Q

Dirofilaria immintis: generic name

A

Canine heart worm

39
Q

Dirofilaria immitus: mode of transmission, infective stage, predilection site of adult, route to predilection site, mode of exit, exiting/diagnostic stage

A

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
Q

Ascaris suum: locations and timing/duration of different stages, when are first eggs passed in feces, how long do adults live

A

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
Q

Ascaris suum: pathology

A

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
Q

Prepatent period definition

A

Time between infection of definitive host and appearance of stage exiting host

43
Q

Ascaris suum: diagnosis

A

**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
Q

Main pathologic events occur during which stage of infection

A

Prepatent

45
Q

Ascaris suum: treatment (3)

A

Pyrantel and fenbendazole = kill migrating larvae
During respiratory phase of infection
Supportive care + tx for secondary infections

46
Q

How long is prepatent period for ascaris suum

A

6-8 weeks

47
Q

How to control prepatent period of ascaris suum

A

Deworming!!

48
Q

Locations of different stages external to host (6)

A

Soil
Water
Vegetation
Fomites
Intermediate host
Paratenic host

49
Q

Ascaricosis of swine: epidemiology

A

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
Q

What information is needed for parasite control (environment)

A

Distribution and numbers of infective stages

51
Q

Environmental assessment: ascaris suum eggs

A

Soil/vegetation samples from pastures
Soil samples from dry lots
Analyzed for eggs

52
Q

Control of ascaris suum (what is the name of this technique)

A

Cleanliness, deworm and wash sows before farrowing
“Dose and move” —> deworm before moving to clean areas, use pasture rotation

53
Q

Environmental conditions that promote development/survival of stages external to host (3)

A

Temperature
Humidity
Shade/exposure to UV light

54
Q

Development/survival of what 4 external stages are affected by environmental conditions

A

Eggs = helminths, ectoparasites
Helminth larvae
Larvae/nymphs of ectoparasites
Protozoan cysts

55
Q

Transmission hiatus

A

When environmental conditions are enough to inhibit growth/survival of parasites so anthelmintic tx not necessary

56
Q

Ascaris suum eggs: winter vs spring (and why this is important for prevention)

A

Winter = eggs accumulate but don’t develop
Spring = eggs develop and become infective
Move pigs to safe pasture before spring rise in temp

57
Q

Environmental conditions that promote and deter ascaris suum egg infection

A

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
Q

Ascaris suum: control strategies to reduce infection rates (2)

A

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
Q

When do ascaris suum eggs become infective

A

2 weeks

60
Q

Geomydoecus heaneyi: generic name, host

A

Chewing louse
1 species of gopher = Llano pocket gopher

61
Q

Eimeria onychomysis: type of parasite, host genus

A

Coccidian
3 known species of grasshopper mice = Onychomys genus

62
Q

Trichostrongylus axei: type of parasite, different hosts

A

Stomach hair worm
Adults in abomasum of ruminants + stomach of horses/swine/humans/rabbits

63
Q

Disease caused by toxoplasma gondii

A

Toxoplasmosis

64
Q

Toxoplasma gondii: definitive hosts, intermediate hosts

A

Definitive = sexual stages restricted to hosts in family Felidae (only felids can shed oocysts produced via sexual reproduction)
Intermediate = mammals and birds

65
Q

Disease caused by schistosoma japonicum

A

Schistosomiasis

66
Q

Schistosoma japonicum: definitive and intermediate hosts

A

Definitive = rodents, Carnivora, ungulates, primates
Intermediate = snails in genus Oncomelania

67
Q

Disease caused by plasmodium reichenowi

A

Malaria

68
Q

Plasmodium reichenowi: definitive and intermediate hosts

A

Definitive = mosquitos in genus Anopheles
Intermediate = chimpanzees

Parasitology (10 decks)

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