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parasitology > Ch. 16 - Schistosomes > Flashcards

Ch. 16 - Schistosomes Flashcards

1
Q

What are the characteristics of schistosomes?

A
  • blood parasites –> feed on RBC
  • dioecious
  • cercariae penetrate skin of definitive host
  • no metacercaria
  • nonoperculate –> embryonated egg that hatches immediately after contacting water
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2
Q

How does the female enter the male schistosome?

A

gynecophoral canal

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3
Q

What 3 species infect humans?

A

1) S. mansoni
2) S. japonicum
3) S. haematobium

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4
Q

What are the differences in the types of schistosomiasis?

A

S. mansoni + S. japonicum:
- hepatic/intestinal

S. haematobium:
- urinary

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5
Q

What are the morphological differences between the 3 species that infect humans?

A

S. mansoni:
- 3-13 testes (male)
- grossly tuberculated tegument (male)
- long reunited ceca (male)
- short uterus (female)
- anterior ovary (female)
- vitelline glands (female)

S. japonicum:
- 6-8 testes (male)
- smooth tegument (male)
- short reunited ceca (male)
- long uterus (female)
- middle ovary (female)

S. haematobium:
- 4-5 testes (male)
- finely tuberculated tegument (male)
- intermediate reunited ceca (male)
- long uterus (female)
- posterior ovary (female)

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6
Q

Where is S. mansoni located in the world?

A

south america, caribbean, middle east, and africa

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7
Q

Where is S. japonicum located in the world?

A

china

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8
Q

Where is S. haematobium located in the world?

A

africa + middle east + india

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9
Q

What is the diagnostic stage?

A

eggs

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10
Q

what is the infective stage?

A

cercariae

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11
Q

What is the life cycle of schistosomas?

A

1) eggs shed in stools or urine
2) eggs hatch releasing miracidia
3) miracidia penetrate snail tissue
4) sporocysts in snail
5) cercariae released by snail into water + free swimming
6) penetrate human skin
7) cercariae lose tails during penetration + become schistosomulae
8) circulation
9) migrate to portal blood in liver + mature into adults

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12
Q

Will cooking food prevent infection of schistosomas?

A

no

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13
Q

What is the 2nd intermediate host of schistosomas?

A

none –> does not have one

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14
Q

What is the location in the definitive host that S. mansoni stays?

A

inferior mesenteric veins –> drain to liver via hepatic portal vein

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15
Q

What is the first intermediate host of S. mansoni?

A

Biomphalaria sp. (snails) –> aquatic

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16
Q

How many eggs per day are released from the oviposition?

A

200 eggs/day/female

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17
Q

what do granulomas do?

A

transport eggs to lumen in S. mansoni

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18
Q

Miracidium penetrates Biomphalaria spp. snails, and does what?

A

gives rise to 2 sporocyst generations:
- mother (1) sporocyst
- daughter (2) sporocyst

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19
Q

Which sporocyst produces cercariae by 30 days?

A

daughter sporocysts

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20
Q

What type of environment are cercaria attracted to?

A

warmth + skin lipids

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21
Q

Describe the “prepatent period”.

A

Adults migrate to mesenteric veins, produce eggs by 5-8 weeks post-infection

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22
Q

Where are the adult S. japonicum located in the human body?

A

superior mesenterics

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23
Q

What is the intermediate host of S. japonicum?

A

Oncomelania hupensis –> amphibious

24
Q

What is the egg production in S. japonicum?

A

2000 eggs/day

25
Q

Which schistosoma species has smaller eggs with small lateral spine?

A

S. japonicum

26
Q

Which schistosoma species has many reservior hosts (a zoonosis)?

A

S. japonicum

27
Q

What is the acute phase of pathogenesis in S. mansoni and S. japonicum?

A
  • Katayama fever
  • PI
  • fever, rash, enlarged liver + spleen
28
Q

What is the chronic phase of pathogenesis in S. mansoni and S. japonicum?

A
  • due to eggs
  • eggs washed into liver in portal circulation
  • soluble egg antigen –> granuloma –> fibrosis
  • hypersensitivity disease
29
Q

Describe Schistosomiasis due to S. mansoni and S. japonicum.

A

1) blockage of blood flow through liver
(8% of cases)
- hemorrhage
2) eggs enter systemic circulation
- blockage of lung capillaries
- CNS lesions
3) gastrointestinal hemorrhage + fibrosis

30
Q

Where are the adult S. haematobium located in the human body?

A

venous plexus surrounding urinary bladder

31
Q

What is unique about the egg morphology in the S. haematobium?

A

conspicuous terminal spine

32
Q

What is the intermediate host of S. haematobium?

A

Bulinus truncatus –> aquatic

33
Q

What is the pathogenesis of S. haematobium?

A
  • granulomas around eggs in wall of bladder + ureters
  • damage to epithelium
34
Q

What does Schistosomiasis due to S. haematobium look like?

A

1) hematuria –> very dangerous
2) fibrosis, calcification of bladder wall + ureters
3) increased pressure on ureters + kidneys –> hydronephrosis
4) squamous cell carcinoma of the bladder
5) increased HIV transmission due to lesions in genital tract –> infertility high among women

35
Q

What does the spine of S. mansoni egg look like?

A

prominent lateral spine

36
Q

What does the spine of S. japonicum egg look like?

A

inconspicuous lateral spine

37
Q

What does the spine of S. haematobium egg look like?

A

terminal spine

38
Q

What is the prevalence of schistosomiasis worldwide?

A

240 million

39
Q

what is the morbidity of schistosomiasis around the world?

A

100-200 million w/symptoms + 20 million w/severe disease

40
Q

what is the mortality of schistosomiasis around the world?

A

200,000/year in sub-sahara africa alone

41
Q

Despite an effective drug, why is schistosomiasis still a problem?

A

1) increased population
2) increased irrigation
3) increased dams

42
Q

What 2 factors contribute to transmission of schistosomiasis?

A

1) contamination of snail habitats w/waste
2) human water contact

43
Q

How can schistosomiasis be controlled?

A

1) snail control –> molluscicides
2) chemotherapy –> praziquantel
3) education

44
Q

What is the immune response?

A

IgE/complement-mediated eosinophil killing

45
Q

What is the immunopathology?

A

immune response to eggs in liver, intestine, and bladder causes disease (hypersensitivity)

46
Q

Describe schistosome dermatitis.

A
  • due to avian schistosomes
  • cercariae penetrate + die in skin –> inflammation –> accidental parasite
  • more severe response w/repeated exposures
47
Q

What does praziquantel do?

A

interferes w/ worm metabolism

48
Q

what does oxamniquine do?

A

works to paralyze worms

49
Q

what does metrifonate do?

A

interferes w/worm metabolism

50
Q

The black pigment in muscle is a response to _________ stage of schistosome.

A

metacercariae

51
Q

The 2nd intermediate host for many non-Schistosome flukes is:

A

fish

52
Q

What form is the Schistosome when it leaves the snail host?

A

cercaria

53
Q

What Schistosome species lives in Asia?

A

Schistosoma japonicum

54
Q

What Schistosome species lives in Brazil?

A

Schistosoma mansoni

55
Q

What Schistosome species lives in Egypt?

A

Schistosoma haematobium

parasitology (9 decks)

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