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Microbiology > Parasitology Exam 2: Nematodes > Flashcards

Parasitology Exam 2: Nematodes Flashcards

1
Q

What is another name for nematodes?

A

Roundworms

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2
Q

Describe nematodes as a whole.

A

Nonsegmented
Elongate
Cylindrical
Well-developed digestive tract and reproductive system

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3
Q

How do nematodes reproduce?

A

Sexually; there are separate nematode sexes (males and females).
- Males smaller than females

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4
Q

List the intestinal nematodes:

A

Ascaris lumbricoides
Enterobius vermicularis (pinworm)
Strongyloides stercoralis (threadworm)
Trichuris trichiura (whipworm)
Ancylostoma duodenale (old world hookworm)
Necator americanus (new world hookworm)

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5
Q

What is a general name for E. vermicularis? What type of helminth is this?

A

Pinworm
Intestinal nematode

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6
Q

What is a general name for S. stercoralis? What type of helminth is this?

A

Threadworm
Intestinal nematode

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7
Q

What is a general name for T. trichiura? What type of helminth is this?

A

Whipworm
Intestinal nematode

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8
Q

What is a general name for A. duodenale? What type of helminth is this?

A

Old World hookworm
Intestinal nematode

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9
Q

What is a general name for N. americanus? What type of helminth is this?

A

New World hookworm
Intestinal nematode

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10
Q

What is the most common and largest roundworm?

A

Ascaris lumbricoides

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11
Q

Describe the life cycle of A. lumbricoides including the transmission, hosts, any important facts

A

Eggs are ingested and hatch in duodenum, penetrate intestinal wall, migrate to hepatic portal circulation, adult worms live and reproduce in the lumen of the small intestine
*Indirect life cycle because transmission is not via a direct route from one host to the next
Transmission: Fecal-oral route

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12
Q

What disease does A. lumbricoides cause?

A

Can cause Loffler syndrome (accumulation of eosinophils in the lungs) or Hepatic ascariasis (hepatic abscesses, obstructive cholangitis)

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13
Q

Laboratory diagnosis of A. lumbricoides

A

ID of eggs or adult worms in feces

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14
Q

What is the infective/diagnostic stage of A. lumbricoides?

A

Infective stage: Ingestion of eggs
Diagnostic stage: ID of eggs in stool

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15
Q

Standout features/morphology of A. lumbricoides eggs

A

Fertile eggs have a thick mamillated shell
Infertile eggs have a thin decorticated shell

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16
Q

Describe the life cycle of E. vermicularis

A

At night, female worm migrates out of anus and lays eggs in perianal region, eggs mature, larvae develop
**Direct life cycle because transmission occurs from an infected host to another individual

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17
Q

How is E. vermicularis transmitted?

A

Ingestion or inhalation of eggs

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18
Q

Which worm discussed most commonly affects school aged children?

A

E. vermicularis

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19
Q

Most common complaint of E. vermicularis

A

perianal itching

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20
Q

Retroinfection of E. vermicularis

A

May occur when eggs hatch and third-stage larvae return to intestine (anus to colon)

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21
Q

Autoinfection of E. vermicularis

A

Embryonated eggs released into the air or hands and are placed into the mouth and swallowed by an already infected patient (anus to mouth)

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22
Q

Infective/diagnostic stage of E. vermicularis

A

Infective: eggs ingested by humans
Diagnostic: eggs on perianal folds

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23
Q

Lab diagnosis of E. vermicularis

A

Microscopic ID of the egg; best obtained using the Scotch tape method

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24
Q

E. vermicularis egg/worm

A

Female has pin shaped tail
Egg is transparent and flat on one side
Gravid = entire body is filled with eggs

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25
Q

Transmission of S. stercoralis

A

Direct penetration of larvae, or person to person

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26
Q

Differentiate filariform vs rhabditiform larvae

A

Filariform: infective larvae that penetrate skin
Rhabditiform: noninfective larvae that can develop into filariform larvae

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27
Q

Describe the life cycle of S. stercoralis

A

Can have a direct, indirect, or autoinfection life cycle. They typically penetrate skin of humans

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28
Q

What is pathenogenesis?

A

A mechanism in which female produces eggs as a form of asexual reproduction in which growth and development occur without fertilization
**Associated with S. stercoralis

29
Q

What is hyperinfection?

A

Increased worm burden in lungs and intestines, can lead to damage to those organs

30
Q

What disease does S. stercoralis cause?

A

Strongyloidiasis, urticarial or serpiginous rash

31
Q

Lab diagnosis of S. stercoralis?

A

Rhabditiform larvae (noninfective form) in stool

32
Q

What organism is associated with “short and sexy”?

A

S. stercoralis because of the short buccal cavity and large genital primordium

33
Q

Which organisms may be identified by their rhabditiform larvae forms? How are they differentiated?

A

S. stercoralis

34
Q

What organism is associated with tracks on agar plates seen as an incidental finding in respiratory specimens?

A

S. stercoralis

35
Q

Trichuris trichiura coinfections can occur with _______ or _______

A

A. lumbricoides or hookworm

36
Q

Transmission of trichuris trichiura

A

Ingestion of eggs

37
Q

Life cycle of T. trichiura

A

Ingestion of eggs –> larvae released into intestine –> mature into adult worms –> eggs passed in feces
NO tissue or pulmonary migration stage, unlike other intestinal nematodes

38
Q

Lab ID of T. trichiura

A

ID of eggs in feces

39
Q

Describe T. trichiura egg (standout words)

A

Barrel shaped, hyaline polar plugs at each end

40
Q

What is the second most common helminthic infection in humans?

A

Hookworms

41
Q

What are the two most common hookworm species and how are they differentiated?

A

A. duodenale (old world hookworm) - well developed mouth parts (looks like teeth)
N. americanus (new world hookworm) - cutting plates
Cannot differentiate species by ID of eggs

42
Q

How are hookworms transmitted?

A

Direct skin penetration by filariform larvae

43
Q

Lab diagnosis of hookworms?

A

Presence of eggs or rhabditiform larvae in stool. Cannot distinguish species by eggs, only know that they are hookworm eggs

44
Q

How to differentiate hookworms from S. stercoralis?

A

Hookworm has a longer buccal cavity and smaller genital primordium

S. stercoralis has a short buccal cavity and large genital primordium

45
Q

List the types of tissue nematodes discussed:

A

Trichinella spp.
Toxocara canis (causes VLM)
Toxocara cati (causes OLM)
A. braziliense/A. caninum (causes CLM)
D. medinensis (Guinea worm)

46
Q

Transmission of Trichinella spiralis

A

Eating undercooked meat, typically pork

47
Q

Key factor of Trichinella spiralis life cycle

A

Parasite remains in striated muscle
Pigs involved in life cycle (ingestion of undercooked pork containing parasite)

48
Q

Trichinosis

A

Disease of the muscle caused by Trichinella infection

49
Q

How is Trichinella spiralis diagnosed in the lab?

A

Encysted larvae via muscle biopsy
Most common way is detection of Ab to Trichinella antigen

50
Q

Infective/diagnostic stage of Trichinella sp.

A

Infective: ingestion of undercooked meat
Diagnostic: larva in striated muscle

51
Q

What disease does T. canis and T. cati cause?

A

Toxocariasis (includes VLM, OLM, CT, NT described on different flashcards)

52
Q

Transmission of T. canis and T. cati

A

Ingestion of eggs

53
Q

Definitive hosts of T. canis and T. cati

A

T. canis = dogs
T. cati = cats

54
Q

Which species states that they CANNOT mature in human host, so wander throughout the body and cause migratory syndromes?

A

T. canis and T. cati

55
Q

What is VLM?

A

Visceral (tissue) larva migrans - may see high eosinophilia
Seen with T. canis/T. cati infections in children

56
Q

What is OLM?

A

Ocular larva migrans - development of granulomatous reaction in retina seen in children with T. canis/T. cati infections

57
Q

What is Covert/common toxocariasis? (CT)

A

Nonspecific symptoms, eosinophilia, positive Toxocara serology (children and adults affected)

58
Q

What is neurotoxocariasis? (NT)

A

Invasion of Toxocara larvae to the brain and spinal cord (seen in childrens and adults)

59
Q

Lab ID of Toxocara infections

A

Visualization of migrating larvae in tissue biopsy, CSF, or ocular fluids

60
Q

What is the diagnostic/infective stage of Toxocara?

A

Diagnostic: larvae in tissues
Infective: ingestion of eggs

61
Q

What are common hookworms of cats and dogs? (aka zoonotic hookworms)

A

A. braziliense and A. caninum

62
Q

What disease does A. braziliense and A. caninum cause, the zoonotic hookworms?

A

CLM (cutaneous larva migrans) aka creeping eruption

63
Q

Definitive host of Toxocara and Ancylostoma

A

Cats and dogs

64
Q

Infective and diagnostic stage of A. caninum and A. braziliense

A

Infective: Skin penetration of worm
Diagnostic: larvae in skin

65
Q

Lab ID of Ancylostoma braziliense and Ancylostoma caninum

A

Evidence of visible tracks and a patient history of possible exposure is usually sufficient

66
Q

What disease does D. medinensis cause and what is another name for it?

A

Guinea Worm
Causes dracunculiasis, blisters caused by gravid female leading to burning and itching

67
Q

Transmission of D. medinensis?

A

Ingestion of freshwater from stagnant ponds containing larvae-infected copepods

68
Q

Lab ID of D. medinensis

A

ID of larvae or adult worms in clinical specimens

Microbiology (24 decks)

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