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Parasitology > Lecture 2: Life Cycles > Flashcards

Lecture 2: Life Cycles Flashcards

1
Q

Definitive host (endoparasites)

A

Host in which adult or sexually reproductive, stages of the parasite occur

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2
Q

Intermediate host (endoparasites)

A

Host required for parasite development but in which parasite does NOT become sexually mature

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3
Q

Paratenic host

A

Host in which the parasite does not undergo any required development but in which it remains alive and infective to another host

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4
Q

Direct life cycle includes a ____ host but no ___ host

A

Includes a definitive host but no intermediate host

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5
Q

What is a monoxenous parasite

A

Parasite with direct life cycles

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6
Q

Are nematodes and Protozoa monoxenous and heteroxenous

A

Monoxenous

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7
Q

What are the two infective stages of a direct life cycle

A

Resting and active stage

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8
Q

Are nematode eggs and protozoan cysts part of the resting stage or active stage for direct life cycle

A

Resting

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9
Q

What is the mode of transmission for resting stage for direct life cycle

A

Ingestion

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10
Q

Are nematode larva and protozoan trophozoite resting or active stage in direct life cycles

A

Active

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11
Q

What is the mode of transmission in active stage of direct life cycle

A

Ingestion, penetration of skin, direct contact

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12
Q

Does an indirect life cycle require an intermediate host?

A

Yes!

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13
Q

Do monoxenous or heteroxenous parasites have an indirect life cycle

A

Heteroxenous

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14
Q

T or F: all trematodes, tapeworms and many parasitic nematodes and Protozoa are monoxenous

A

False! These are all heteroxenous

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15
Q

What are the two infective stages of an indirect life cycle

A

Resting and active

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16
Q

Is an encysted larvae in the resting infective stage for indirect life cycle or active stage

A

Resting

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17
Q

What is the mode of transmission for resting stage indirect life cycle

A

Ingestion

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18
Q

Are helminth larva and protozoan trophozite in active or resting infective stage

A

Active

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19
Q

What is the mode of transmission for parasites in active stage indirect life cycle

A

Penetration of the skin, via a vector

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20
Q

Describe the basic pathway of direct life cycle

A
  1. Animal ingest infective egg
  2. Larvae are established in the small intestine and become patent over a specific period of time
  3. Unembryonated eggs passed in feces
  4. Cycle repeats
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21
Q

Describe the basic indirect life cycle

A
  1. Parasite infects or is ingested by intermediate host
  2. Intermediate host is either ingested by definitive host or bites definitive host
  3. Definitive host gets parasite
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22
Q

Are paratenic host required for completion of parasites life cycle

A

No!

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23
Q

What is the main role of paratenic host

A

Facilitates transmission to definitive host

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24
Q

What is stephanurus denatatus

A

Swine kidney worm

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25
Q

Is stephanurus dentatus monoxenous or heteroxenous

A

Monoxenous nematode

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26
Q

What nematode do earthworms act as paratenic hosts and how does this work

A

Earthworms are paratenic host for Stephanurus dentatus (swine kidney worm)

Paratenic hosts facilitate transmission so definitive host will ingest earthworm and therefore S. dentatus

27
Q

What are the 4 modes of transmission for stephanurus denatatus

A
  1. Ingestion of free infective larvae (main mode)
  2. Ingestion of earthworm (paratenic host) carrying infective larvae
  3. Penetration of skin by infective larvae
  4. Transplacental transmission
28
Q

Arthropod ectoparasites serve as ____ and ___

A

Parasites and vectors

29
Q

What are the two main life cycles for ectoparasites

A
  1. Holometabolous (complete) metamorphosis
  2. Hemimetabolous (incomplete, simple) metamorphosis
30
Q

What is holometabolous metamorphosis

A

Egg—> larva—> pupa—> adult

31
Q

Which type of ectoparasites metomorphosis has differing larval and adult morphology

A

Holometabolous

32
Q

What is hemimetabolous metamorphosis

A

Egg—> larva—> nymph—> adult

OR

egg—> nymph—> adult

33
Q

Which type of ectoparasites metamorphosis has similar larval and adult morphology

A

Hemimetabolous

34
Q

Are fleas and dipeterans holometabolous or hemimetabolous

A

Holometabolous

35
Q

Are ticks, mites and lice holometabolous or hemimetabolous

A

Hemimetabolous

36
Q

What 6 key points can we gain from life cycles of parasites

A
  1. Mode of transmission to host
  2. Stage infecting/infesting the host
  3. Predilection site of adult stage in/on host
  4. Route of predilection site
  5. Mode of exit from host
  6. Stage exiting host
37
Q

What is dirofilaria immitis

A

Canine heartworm

38
Q

What is the mode of transmission for dirofilaria immitis

A

Vectored by mosquitoes (Culex, aedes, anopheles)

39
Q

What is the infective stage for dirofilaria immitis

A

Third stage larva (L3); migrates through mosquito bite wound

40
Q

What is the predilection site of adult with dirofilaria immitis

A

Pulmonary arteries, right ventricle

41
Q

What is the route to the predilection site for dirofilaria immitis

A

Venous circulation (from subcutis and abdominal/thoracic muscles)

42
Q

What is the mode of exit for dirofilaria immitis

A

Blood ingested by mosquito

43
Q

What is the exiting/diagnostic stage for dirofilaria immitis

A

Microfilaria in the blood

44
Q

Ascaris suum causes what pathology to the liver and lung

A

Milk spots to liver and severe lung damage

45
Q

How can the pathology caused by Ascaris suum in the lungs, liver and small intestine be helpful in identifying life cycle and treatment

A

Milk spots in liver:LARVAE- migrating through liver causing hemorrhage, fibrosis and lymphocyte infiltration

Lung damage: LARVAE- migrating causing hemorrhage, eosinophilic infiltration, edema, pneumonia

Small intestine: MATURING AND ADULT WORMS- cause inflammation, diarrhea, perforate small intestine, loss of nutrients

46
Q

What is the prepatent period

A

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

47
Q

What stage/how would parasite appear during prepatent period

A

Egg, cyst

48
Q

What is the best method to control life cycles during prepatent period

A

Deworming

49
Q

What are some different locations where parasite stages can occur external to the host

A

Soil, water, vegetation, intermediate host

50
Q

What environmental conditions promote development of survival stages

A

Temperature, humidity, shade

51
Q

How can you use the environment to control and prevent parasitic diseases

A

Exposure to intense sunlight, suboptimal temperatures (temps below 15 degrees Celsius decrease egg survival)

52
Q

What type of parasite usually only occur in 1 host species

A

Many lice

53
Q

What type of parasites can occur in more than 1 host species but are restricted to family or species

A

Coccidia

54
Q

What type of parasite can occur in more than 1 family or orders or hosts

A

Trichostrongylus axei

55
Q

what are 3 examples of parasites with indirect lifecycles that can have varying host specificity at different stages

A
  1. Toxoplasma gondii
  2. Schisotosoma japonicum
  3. Plasmodium reichenowi
56
Q

What is the definitive host for toxoplasma gondii

A

Felids

57
Q

What is the intermediate host for toxoplasma gondii

A

Mammals and birds (broad host range)

58
Q

What is the definitive host for schistosoma japonicum

A

Rodents, carnivores, ungulates, primates and other mammals (broad host range)

59
Q

What is the intermediate host for schistosoma japonicum

A

Snails in the genus oncomelania (narrow host range)

60
Q

What is plasmodium reichenowi

A

Malaria

61
Q

What is the definitive host for plasmodium reichenowi

A

Mosquitoes in the genus anopheles (narrow host range)

62
Q

What is the intermediate host for plasmodium reichenowi

A

Chimpanzees (narrow host range)

63
Q

Why is it important to know the life cycle

A
  1. Diagnose disease and ID parasite
  2. Predict what pathogenic changes occurs
  3. Optimize treatment to improve control (which animals to treat/when to treat)
  4. Develop environmental control programs
  5. Reduce cross-species (including zoonotic) infections

Parasitology (28 decks)

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