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Liz's Parasitology Course > Intestinal Nematodes > Flashcards

Intestinal Nematodes Flashcards

1
Q

List the general characteristics of nematodes

A
  • Nonsegmented
  • Tapered at both ends
  • Tough, protective coating of cuticle
  • Separate sexes
  • Fairly long-living (years)
  • Diagnosis usually by finding eggs in feces
  • Severity often related to the # of worms
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2
Q

Life cycle of nematodes

A
  • Some have free-living form of larvae (rhabditiform larva) → infective form (filariform larva)
  • Some can’t be free-living → infective stage is shed (person to person)
  • No intermediate hosts (human is the definitive host for medically important roundworms)
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3
Q

Common name for Ascaris

A

None

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4
Q

Diagnostic form of Ascaris

A

Eggs

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5
Q

Infective form of Ascaris

A

Eggs ingested from soil, food, water

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6
Q

Which stage of the Ascaris life cycle is most commonly seen in the clinical specimen from an infected patient?

A

Adults can emerge from human nose, mouth, or anus

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7
Q

Clinical manifestation of Ascaris

A
  • Sometimes asympatomatic
  • Asthmatic (allergic rxn to parasite)
  • Pneumonitis
  • Bowel obstruction
  • Adults may migrate to other tissues
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8
Q

Describe the microscopic appearance of Ascaris

A
  • Oval eggs, often stain brown in stool
  • Infertile eggs are elongated, bizarre shaped (no male present)
  • Mammilated coat = lumpy bumpy
  • Decorticated = lost coat
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9
Q

Common name for the Ancylostoma duodenale/Necator americanus

A

Hookworm

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10
Q

Diagnostic form of Ancylostoma duodenale/Necator americanus

A

Eggs, rhabditiform larvae

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11
Q

Infective form of Ancylostoma duodenale/Necator americanus

A

Filariform larvae

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12
Q

Which stage of Ancylostoma duodenale/Necator americanus is most commonly seen in clinical specimens from an infected patient?

A

Adult worms secrete anticoagulant and ingest blood → anemia

- Hemorrhages at site of attachment

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13
Q

Clinical manifestation of Ancylostoma duodenale/Necator americanus

A
  • Bronchitis (large #s) but no sensitization like Ascaris
  • Diarrhea, fever, nausea, vomiting
  • Can cause mental/physical development impairment in children
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14
Q

Describe the microscopic appearance of Ancylostoma duodenale/Necator americanus

A
  • Eggs in stool → oval, colorless, thin-shelled
  • Filariform larvae → pointed tail
  • Rhabditiform larvae → small genital primordium and longer buccal cavity
  • Adult
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15
Q

Differentiate Ancylostoma and Necator in diganosis of hookworm adults

A
  • Ancylostoma has two pairs of cutting teeth

- Necator has cutting plates

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16
Q

What intestinal nematode causes “creeping eruption”/”cutaneous larvae migrans” in humans?

A

Ancylostoma duodenale/Necator americanus

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17
Q

Clinical manifestation of “creeping eruption”

A
  • Larvae migrate through subcutaneous tissues causing irritation
  • Dog or cat hookworm
  • Secondary infections
  • Animals, beaches/sandboxes and bare feet
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18
Q

Common name for Strongyloides stercoralis

A

Threadworm

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19
Q

Diagnostic form of Strongyloides stercoralis

A

Rhabditiform, sometimes eggs

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20
Q

Infective form of Strongyloides stercoralis

A

Filariform

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21
Q

Which stage of Strongyloides stercoralis is most commonly seen in clinical specimens from an infected patient?

A

Rhabitiform larvae

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22
Q

Clinical manifestation of Strongyloides stercoralis

A
  • Usually mild/no symptoms unless immunocompromised (disseminated strongyloidiasis or hyperinfection)
  • Nausea, vomiting, sharp pains (ulceration)
  • Rarely skin irritation at site of entry
  • Non-bacterial pneumonia w/ eosinophilia, respiratory failure (immunocompromised patients)
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23
Q

Describe the microscopic appearance of Strongyloides stercolaris

A
  • Eggs rarely seen in stool (resembles hookworm)!
  • Rhabditiform larvae sometimes in stool; short buccal cavity, large genital primordium (SHORT AND SEXY)
  • Use sedimentation technique
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24
Q

Common name for Enterobius vermicularis

A

Pinworm (sharply pointed tail of female)

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25
Q

Diagnostic form of Enterobius vermicularis

A

Eggs (no fecal specimens)

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26
Q

Infective form of Enterobius vermicularis

A

Eggs (no external maturation required)

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27
Q

Which stage of Enterobius vermicularis is most commonly seen in clinical specimens from an infected patient?

A

Eggs

28
Q

Clinical manifestation of Enterobius vermicularis

A
  • Often asymptomatic
  • Anal itching (pruritus), loss of sleep
  • May be loss of appetite, nausea, vomiting
29
Q

Describe the microscopic appearance of Enterobius vermacularis

A
  • Eggs = oval, slightly flattened, w/ thin, smooth, colorless shell; usually internal larvae can be seen
  • Adult female = pointed tail (male tail is curved), alae (3 lips)
30
Q

Common name for Trichuris trichiura

A

Whipworm

31
Q

Diagnostic form of Trichuris trichiura

A

Eggs

32
Q

Infective form of Trichuris trichiura

A

Eggs

33
Q

Which stage of Trichuris trichiura is most commonly seen in clinical specimens from an infected patient?

A

Eggs passed in stool (occasionally adult)

34
Q

Clinical manifestation of Trichuris trichiura

A
  • Light infections may be asymptomatic

- Heavy infections: diarrhea, weight loss, pain, bleeding, anemia, PROLAPSED RECTUM in repeated infections

35
Q

Describe the microscopic appearance of Trichuris trichiura

A

Barrel-shaped eggs, w/ polar plugs at each end, unembryonated

36
Q

Common name for nematodes

A

Roundworms

37
Q

Know the sizes of the eggs for each Nematode discussed

A
  • Strongyloides stercolaris (40-85um)
  • Ascaris (45-75um)
  • Trichuris trichiura (50um)
  • Hookworm (50-60um)
  • Enterobius vermicularis (55um)
38
Q

Arrange the adult nematode worms from smallest to largest in relative size

A
  • Strongyloides stercolaris
  • Enterobius vermicularis
  • Hookworm
  • Trichuris trichiura
  • Ascaris
39
Q

Describe the method of choice for obtaining pinworm specimens

A

Cellophane tape preparation or paddle

  • When first wakening (before showering)
  • Clear tape (not frosted) placed over end of tongue depressor (sticky side out)
  • Perianal area touched with sticky tape, then tape stuck to slide
40
Q

Widespread (warm climates, associated w/ poor sanitation

A

Ascaris

41
Q

Which type of hookworm is still prevalent in rural areas of U.S. (Kentucky and South)

A

Necator americanus

42
Q

Which nematode is associated w/ lung involvement?

A
  • Hookworm
  • Ascaris
  • Strongyloides stercoralis
43
Q

Which nematode is associated w/ ground itch at site of penetration?

A

Hookworm

44
Q

Which Nematode is found in some areas of Appalachia or rural Southeastern U.S. and doesn’t need a host?

A

Strongyloides stercoralis

45
Q

How do we get autoinfection in Strongyloides stercoralis?

A

Larvae penetrate intestine or perianal skin → circulation

46
Q

The only organism that is agar plate cultured

A

Strongyloides stercoralis

47
Q

Describe the Agar plate culture in Strongyloides stercoralis

A
  • Stool is placed on agar plate
  • Incubate @ RT for 2 days
  • Larvae will migrate over agar, carrying bacteria, leaving visible tracks
  • Wash plate with formalin & examine larvae for ID
48
Q

Most common Nematode in the U.S

A

Enterobius vermicularis

49
Q

This nematode mostly found in families or crowded conditions by inhalation or ingestion of eggs or retroinfection and children most often infected.

A

Enterobius vermicularis

50
Q

This Nematode is found worldwide and southern U.S.

A

Trichuris trichiura

51
Q

Which Nematode is associated w/ infections acquired through the skin?

A
  • Hookworm

- Strongyloides stercolaris

52
Q

Which Nematode is associated w/ “ground itch”?

A

Hookworm

53
Q

Which Nematode is associated w/ anal pruritis?

A

Enterobius vermicularis

54
Q

Which Nematode is associated w/ prolapsed rectum?

A

Trichuris trichiura

55
Q

Which Nematode is associated w/ “creeping eruption” or cutaneous larvae migrans (CLM)?

A

Ancylostoma duodenale/Necator americanus

56
Q

Which Nematode is associated w/ bowel obstruction?

A

Ascaris

57
Q

Which Nematode is associated w/ anemia from adult worms excreting anticoagulant?

A

Ancylostoma duodenale/Necator americanus

58
Q

Which Nematode is associated w/ appearance of adult from human mouth or nose?

A

Ascaris

59
Q

Which Nematodes are seen in patients who have NOT been outside the U.S.

A

??

60
Q

How is Ascaris acquired??

A

(D) Eggs passed → develop into infective stage (embryonated eggs) →(I) eggs ingested → hatch in intestine → larvae penetrate intestines → blood or lymphatics → liver, heart → filtered by lungs → esophagus (swallowed) → small intestine → mature to adults and lay eggs

61
Q

How is Ancylostoma duodenale/Necator americanus acquired??

A

(D) Eggs passed → moist soil → (D) rhabditiform larvae → (I) filariform larvae → penetrate skin of humans (foot) or ingested → circulation → lung, trachae, esophagus (swallowed) → attachment in intestine → mature to adults that lay eggs

62
Q

How is Strongyloides stercoralis acquired??

A

(D) Rhabditiform larvae passed in feces → adults produce eggs in soil → (I) filariform larvae penetrate skin → circulation → lung, trachae, esophagus (swallowed) → adults produce eggs in intestines → eggs hatch into rhabditiform larvae OR autoreinfection

63
Q

How is Enterobius vermicularis acquired?

A
  • Female migrates outside of anus at night to lay eggs

- Eggs are infective w/in hours (no external maturation required) → USE LAB CAUTION!

64
Q

How is Trichuris trichiura acquire??

A

(D) Eggs passed → eggs embryonate in soil → (I) eggs ingested → larvae released in intestine → larvae mature to adult → adult female attaches to intestine and lays eggs

65
Q

This Nematode has the thickness of a pencil; cuticle has circular striations and is creamy white

A

Ascaris

66
Q

Since eggs and larvae of two genera are indistinguishable in hookworm, how can we report that?

A

Report as “hookworm”

67
Q

Which form of Strongyloides stercoralis is seen in sputum in immunocompromised patients?

A
  • Filariform larvae → notched tail; seen in sputum (immunocompromised patients)

Liz's Parasitology Course (8 decks)

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