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Microbiology > Parasitology Exam 2: Nematodes > Flashcards

Parasitology Exam 2: Nematodes Flashcards

(68 cards)

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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
Transmission of S. stercoralis
Direct penetration of larvae, or person to person
26
Differentiate filariform vs rhabditiform larvae
Filariform: infective larvae that penetrate skin Rhabditiform: noninfective larvae that can develop into filariform larvae
27
Describe the life cycle of S. stercoralis
Can have a direct, indirect, or autoinfection life cycle. They typically penetrate skin of humans
28
What is pathenogenesis?
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
What is hyperinfection?
Increased worm burden in lungs and intestines, can lead to damage to those organs
30
What disease does S. stercoralis cause?
Strongyloidiasis, urticarial or serpiginous rash
31
Lab diagnosis of S. stercoralis?
Rhabditiform larvae (noninfective form) in stool
32
What organism is associated with "short and sexy"?
S. stercoralis because of the short buccal cavity and large genital primordium
33
Which organisms may be identified by their rhabditiform larvae forms? How are they differentiated?
S. stercoralis
34
What organism is associated with tracks on agar plates seen as an incidental finding in respiratory specimens?
S. stercoralis
35
Trichuris trichiura coinfections can occur with _______ or _______
A. lumbricoides or hookworm
36
Transmission of trichuris trichiura
Ingestion of eggs
37
Life cycle of T. trichiura
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
Lab ID of T. trichiura
ID of eggs in feces
39
Describe T. trichiura egg (standout words)
Barrel shaped, hyaline polar plugs at each end
40
What is the second most common helminthic infection in humans?
Hookworms
41
What are the two most common hookworm species and how are they differentiated?
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
How are hookworms transmitted?
Direct skin penetration by filariform larvae
43
Lab diagnosis of hookworms?
Presence of eggs or rhabditiform larvae in stool. Cannot distinguish species by eggs, only know that they are hookworm eggs
44
How to differentiate hookworms from S. stercoralis?
Hookworm has a longer buccal cavity and smaller genital primordium S. stercoralis has a short buccal cavity and large genital primordium
45
List the types of tissue nematodes discussed:
Trichinella spp. Toxocara canis (causes VLM) Toxocara cati (causes OLM) A. braziliense/A. caninum (causes CLM) D. medinensis (Guinea worm)
46
Transmission of Trichinella spiralis
Eating undercooked meat, typically pork
47
Key factor of Trichinella spiralis life cycle
Parasite remains in striated muscle Pigs involved in life cycle (ingestion of undercooked pork containing parasite)
48
Trichinosis
Disease of the muscle caused by Trichinella infection
49
How is Trichinella spiralis diagnosed in the lab?
Encysted larvae via muscle biopsy Most common way is detection of Ab to Trichinella antigen
50
Infective/diagnostic stage of Trichinella sp.
Infective: ingestion of undercooked meat Diagnostic: larva in striated muscle
51
What disease does T. canis and T. cati cause?
Toxocariasis (includes VLM, OLM, CT, NT described on different flashcards)
52
Transmission of T. canis and T. cati
Ingestion of eggs
53
Definitive hosts of T. canis and T. cati
T. canis = dogs T. cati = cats
54
Which species states that they CANNOT mature in human host, so wander throughout the body and cause migratory syndromes?
T. canis and T. cati
55
What is VLM?
Visceral (tissue) larva migrans - may see high eosinophilia Seen with T. canis/T. cati infections in children
56
What is OLM?
Ocular larva migrans - development of granulomatous reaction in retina seen in children with T. canis/T. cati infections
57
What is Covert/common toxocariasis? (CT)
Nonspecific symptoms, eosinophilia, positive Toxocara serology (children and adults affected)
58
What is neurotoxocariasis? (NT)
Invasion of Toxocara larvae to the brain and spinal cord (seen in childrens and adults)
59
Lab ID of Toxocara infections
Visualization of migrating larvae in tissue biopsy, CSF, or ocular fluids
60
What is the diagnostic/infective stage of Toxocara?
Diagnostic: larvae in tissues Infective: ingestion of eggs
61
What are common hookworms of cats and dogs? (aka zoonotic hookworms)
A. braziliense and A. caninum
62
What disease does A. braziliense and A. caninum cause, the zoonotic hookworms?
CLM (cutaneous larva migrans) aka creeping eruption
63
Definitive host of Toxocara and Ancylostoma
Cats and dogs
64
Infective and diagnostic stage of A. caninum and A. braziliense
Infective: Skin penetration of worm Diagnostic: larvae in skin
65
Lab ID of Ancylostoma braziliense and Ancylostoma caninum
Evidence of visible tracks and a patient history of possible exposure is usually sufficient
66
What disease does D. medinensis cause and what is another name for it?
Guinea Worm Causes dracunculiasis, blisters caused by gravid female leading to burning and itching
67
Transmission of D. medinensis?
Ingestion of freshwater from stagnant ponds containing larvae-infected copepods
68
Lab ID of D. medinensis
ID of larvae or adult worms in clinical specimens

Microbiology (24 decks)

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