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Microbiology Exam 3 > 37 - Parasitic Roundworm Infections of the GI Tract > Flashcards

37 - Parasitic Roundworm Infections of the GI Tract Flashcards

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Biology 101 flashcards
1
Q

What are helminths?

A

Worms

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2
Q

What are Nematodes?

A

Round worms

  • Non-segmented bodies
  • Separate sexes
  • Complete digestive systems
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3
Q

What are Cestodes?

A

Tapeworms

  • Segmented bodies
  • Hermaphroditic
  • Absorb nutrients
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4
Q

What are Trematodes?

A

Flukes

  • Non-segmented (leaf)
  • Hermaphroditic
  • Primitive gut
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5
Q

What is the most common type of parasitic helminth in the US and the world?

A

Nematodes

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6
Q

Are nematodes typically fatal?

A

No, however they do contribute to malnutrition and a diminished work capacity

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7
Q

Where do we most commonly see Nematodes?

A
  • Areas of poor sanitation
  • Developing countries
  • Tropics
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8
Q

What population is most likely to develop a symptomatic nematode infection?

A

Children

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9
Q

What is disease typically caused by?

A

The presence of adult forms of the worms in the GI tract

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10
Q

Are these infections common in the US?

A

Yes, relatively common

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11
Q

What stages does the life cycle of a nematode consist of?

A
  • Egg
  • Multiple larval
  • Adult stages
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12
Q

Are there different sexes in nematodes?

A

Yes - the female is usually larger than the male

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13
Q

What needs to happen in order for an individual to be shedding INFECTIOUS eggs?

A

There needs to be a male and a female, 2 or more worms

A female alone can shed eggs, but not fertilized, infectious eggs

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14
Q

Do adult worms replicate themselves in humans?

A

No - worms lay eggs, but the adult worms do NOT replicate

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15
Q

How do we identify and diagnost nematodes?

A

They are identified by the characteristic morphology of their EGGS

KNOW YOUR EGGS!

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16
Q

Some GI nematodes pass through other tissues. What other tissues can be infected during development?

A

Lungs and skin

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17
Q

What is a good laboratory clue that your patient is infected with a nematode?

A

Increased levels of eosinophils

They are an immune response that fight off helminth infections

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18
Q

What is the most comon helminthic infection encountered in the US?

A

Pinworm or Enterobius vermicularis

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19
Q

What types of nematode infections fall in the category of Geohelminths?

A
  • Nemotode infections that are acquired through contact with infected soil
  • Larvae or eggs require a period of time to develop in warm, moist soil
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20
Q

There are two groups of geohelminths. What are they?

A

Ingestion of an infectious egg

  • Ascaris
  • Trichuris

Penetration of the skin by an infectious larvae found in the soil

  • Strongyloides
  • Hookworms
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21
Q

How do these helminths get in the soil?

A

Inadequate disposal of human waste, contamination of water supplies with sewage or the use of human waste as fertilizer

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22
Q

What is the life cycle of a Pinworm or Enterobius vermicularis?

A

1 - Ingestion of an embryonated egg in the infective stage
2 - Egg hatches in the small intestine and the larva moves to the large intestine
3 - The larva penetrates the mucosa and develops there
4 - They mature to adults within 2-6 weeks
5 - Females migrate to the perianal region to lay eggs at night
6 - Males live in the cecum of the lumen
7 - Eggs are laid on the perianal folds, allowing for diagnosis of the infection

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23
Q

How is a Pinworm or Enterobius vermicularis infection transmitted?

A

Fecal-oral route

- By the ingestion of eggs

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24
Q

Why is reinfection common?

A

It can be easily transmitted within families

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25
Q

Can pinworms of other animals (the family dog) infect humans?

A

No

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26
Q

Are most Pinworm or Enterobius vermicularis symptomatic or asymptomatic?

A

Asymptomatic

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27
Q

When you do have a symptomatic infection, what will you see?

A
  • Perianal itching
  • Possibly a secondary bacterial infection from a lesion
  • Some studies show appendicities (possible)
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28
Q

How do you diagnose a Pinworm or Enterobius vermicularis infection?

A

Identification of eggs or the appearance of adult worms in the perianal region

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29
Q

What does an egg from a Pinworm or Enterobius vermicularis infection look like?

A

Flat sided eggs

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30
Q

How can you see the eggs?

A

The scotch tape prep

View with microscope

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31
Q

How do you control and prevent a Pinworm or Enterobius vermicularis infection?

A
  • Several anti-helminthic compounds
  • Usually a single dose, repeated again 2 weeks later
  • Good hygiene and housekeeping
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32
Q

What drugs can you use to treat a Pinworm or Enterobius vermicularis infection?

A
  • Mebendazole

- Pyrantel pamoate

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33
Q

Should you treat all household members?

A

Used to be the recommendation, not really anymore

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34
Q

The pinworm poem…

A

The pinworm is a parasite
That makes a journey every night,
From the intestine where it resides
To lay its eggs on the outside.

The usual symptom is an itchy bottom
Though in the appendix it can cause a problem.
It generally resides in tiny tots,
But can infect both moms and pops.

Its thin walled eggs float in the air
So they can end up anywhere.
So if tonight you start to squirm,
remember it might be this worm.

But, this nematode’s easy to diagnose
By affixing scotch tape to the host;
Then examining the microscopic slide
For eggs that are flatter on one side.

So if you have him, don’t be embarrassed
Anyone can have Enterobius vermicularis.

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35
Q

What is the trichuris trichiura parasite commonly called?

A

Whipworm because of its “whip-like” appearance

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36
Q

How much of the world’s population is infected with whipworm or trichuris trichiura?

A

One quarter (25%)

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37
Q

What regions in the US do we see whipworm or trichuris trichiura infections?

A

Mostly tropical - found in Southeast US

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38
Q

How do you transmit whipworm or trichuris trichiura?

A

The fecal-oral route

  • Contaminated soil
  • Warm, moist soil promotes the development of eggs
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39
Q

What percent of infections of whipworm or trichuris trichiura are asymptomatic?

A

90%

40
Q

What do you see in a symptomatic infection of whipworm or trichuris trichiura?

A
  • Heavy worm burden (more than 200 worms in the body)
  • Bloody, mucus containing diarrhea
  • Frequent stools
  • Rectal prolapse in children
  • May contribute to growth retardation and anemia in children
41
Q

How do you diagnose whipworm or trichuris trichiura?

A

Identification of eggs in the stool

42
Q

How do you control or prevent whipworm or trichuris trichiura?

A

Proper sanitation and personal hygiene

43
Q

What is ascaris lumbricoides commonly called?

A

Ascariasis

44
Q

What is the life cycle of ascariasis or ascaris lumbricoides like?

A

Complicated

  • Ingestion of eggs that have developed in the external environment over the course of 10-14 days
  • The ingested eggs are in the infective stage
  • They live in the lungs for 10-14 days
  • They are coughed up and swallowed
  • Adult ascariasis worms develop in the lumen of the small intestine
  • Adults begin producing eggs
  • Unfertilized eggs are found in feces and used for diagnosis
  • The egg becomes fertilized in the environment, forms a two cell-stage, then undergoes advanced cleavage before being ingested in the infective stage
45
Q

What is a key feature of a ascariasis or ascaris lumbricoides infection?

A

They are the largest, longest type of roundworm

You can actually see them and they’re big

46
Q

How many people in the world are infected?

A

1 billion

Including a few million Americans in the Southeast

47
Q

How are ascariasis or ascaris lumbricoides transmitted?

A

Via the fecal-oral route

  • Contaminated human feces
  • Eggs need to develop in the soil before they are infective
48
Q

Are humans the only reservoir for ascariasis or ascaris lumbricoides?

A

YES

The pig form rarely infects humans

49
Q

Are most ascariasis or ascaris lumbricoides infections symptomatic or asymptomatic?

A

Asymptomatic

50
Q

What will you see in the symptomatic disease?

A

A range from abdominal discomfort to death (rare)

51
Q

What intestinal disease will you see with ascariasis or ascaris lumbricoides?

A
  • The physical presence of adult worms in the small intestine
  • Abdominal pain, indigestion, loss of appetite, vomiting, diarrhea
52
Q

What will heavy ascariasis or ascaris lumbricoides infections cause?

A

A physical obstruction

53
Q

What is the main concern when children have a ascariasis or ascaris lumbricoides infection?

A

Nutritional deficiency and growth retardation

54
Q

What pulmonary disease will ascariasis or ascaris lumbricoides cause?

A

A combination of the physical presence and the immune response to the worms results in the following symptoms:

  • Mild cough
  • Pneumonitis (inflammation of the alveoli)
55
Q

Why will we see these pulmonary symptoms?

A

Because parasite antigens are highly allergenic

Repeated exposure can cause an asthmatic attack

56
Q

What is another clinical diagnostic test you can use to help with identification?

A

Eosinophilia is common

57
Q

How do you diagnose ascariasis or ascaris lumbricoides specifically?

A
  • Eggs found in stool

- Larvae or eosinophils found in the sputum

58
Q

How do you control and prevent ascariasis or ascaris lumbricoides infections?

A

Sanitation and hygiene

59
Q

What do we commonly call a Necator americanus or Ancylostoma duodenale infection?

A

Hookworm

60
Q

How many people in the world are infected with hookworm?

A

1 billion

61
Q

What is hookworm (Necator americanus or Ancylostoma duodenale) a major contributor to?

A

Anemia in children and pregnant women

62
Q

Where is Necator americanus found?

A

Southeast US

63
Q

How is hookworm (Necator americanus or Ancylostoma duodenale) transmitted?

A

Larvae from fecal contamination of soil that are able to penetrate intact skin

64
Q

Are there any animal reservoirs for human hookworms?

A

NO

65
Q

What causes the anemia in hookworm?

A

Iron-deficiency anemia due to blood loss from hookworm feeding. If infection is severe enough this can result in fatigue, exertional dyspnea, koilonychias (brittle, spoon shaped nails), pale sclera, and heart murmurs.

66
Q

What can happen to children infected with hookworm?

A

Children with severe infection can become protein malnourished due to blood loss.

67
Q

What is “ground itch”?

A

Penetration of the skin - moderate dermatitis (“ground itch”).

68
Q

What are two diseases that may accompany the larval passage though the lungs in a hookworm infection?

A

Pneumonia and eosinophilia

69
Q

Which form of hookworm (Ancyclostoma or Necator) is more pathogenic?

A

Ancyclostoma

Ancylostoma consumes more blood than Necator; therefore it is usually considered more pathogenic.

70
Q

How do you diagnose hookworm?

A

Presence of egg in the stool

71
Q

How do you distinguish between Necator and Ancylostoma?

A

Distinguishing between Necator and Ancylostoma requires and examination of adult worms or larvae.

72
Q

How do you prevent hookworm?

A

Sanitation and wearing shoes!

73
Q

What do we commonly call a Strongyloides stercoralis infection?

A

Strongyloidiasis

74
Q

What is the patient shedding in the stool?

A

Actual larvae

They will develop into free living eggs in the SOIL, not in your intestine

75
Q

How big is a Strongyloidiasis or Strongyloides stercoralis worm?

A

It is the smallest of all nematodes (1-2 mm)

76
Q

How many people world wide are infected with Strongyloidiasis or Strongyloides stercoralis?

A

50-100 million people

Mostly in the Southeast US and appalachia regions

77
Q

What is a UNIQUE feature of Strongyloidiasis or Strongyloides stercoralis?

A

It can multiply in the host and in the environment

It is FREE living

78
Q

How is a Strongyloidiasis or Strongyloides stercoralis infection transmitted?

A

Penetration of the skin by infectious larvae

79
Q

What is meant by auto-infection or re-initiate infection of Strongyloidiasis or Strongyloides stercoralis?

A

Infectious form larvae can develop in the intestine, penetrate the intestine, enter the bloodstream, and re-initiate infection (auto-infection).

80
Q

Are the symptoms of Strongyloidiasis or Strongyloides stercoralis typically severe?

A

No

There is a low worm burden, resulting in little symptomology

81
Q

What are they symptoms of Strongyloidiasis or Strongyloides stercoralis if they arise?

A

Non-specific symptoms

  • Epigastric pain and tenderness
  • Bloating
  • Heartburn
82
Q

What will you see in the pulmonary stage of infection in Strongyloidiasis or Strongyloides stercoralis?

A

Pulmonary inflammation (eosinophilia)

83
Q

What results in a hyperinfection from Strongyloidiasis?

A

Abrogation of the immune defenses

84
Q

What is the process of abrogation of the immune defense?

A

increased numbers of filariform larvae leave the intestine resulting in a worsening of intestinal (diarrhea) as well as pulmonary symptoms.

85
Q

What will result when a hyperinfection leads to a disseminated infection?

A

hyperinfection can develop into disseminated infection, resulting in the migration of larvae not only to the lungs and GI tract, but also the CNS, peritoneum, liver and kidney.

86
Q

What populations do we see a disseminated strogyloidiasis infection in?

A

Individuals undergoing immunosuppressive therapy (glucocorticoides)

87
Q

How do you diagnose strongyloidiasis infections?

A

Detection of LARVAE in the stool… Not eggs

** This is UNIQUE **

88
Q

How do you prevent a strongyloidiasis infection?

A

Sanitation
Hygiene
Wear shoes

89
Q

What type of infection will present with eggs that are flat on one side?

A

Pinworm

Enterobius vermicularis

90
Q

What type of infection will present with eggs that are lemon or barrel shaped?

A

Trichuris trichiura

91
Q

What type of infection will present with lumpy, bumpy eggs?

A

Ascaris lumbricoides (fertile)

92
Q

What type of infection will present with boring/plain eggs?

A

Hookworm

93
Q

A 36-year-old woman with a history of travel to Puerto Rico submitted a routine stool specimen. The images below were captured during wet mount examination of the concentrate from a stool specimen. The images are not on the same scale (see below). What is your diagnosis? Based on what criteria?

A

Ascaris and Trichuris

94
Q

A 30-year-old woman discovered a worm in her stool (Figure A). She took the specimen to her doctor, reporting no symptoms or international travel. The specimen was preserved in 10% formalin and sent to CDC for identification.

Long, big worm

A

Ascaris

95
Q

A concentrate (formalin-ethyl acetate technique) of a stool specimen was preserved in formalin. Figures A and B show a bright-field examination of the wet mount. The objects measured approximately 300 micrometers in length. What is your diagnosis? Based on what criteria?

A

Strongyloides

larvae, NOT eggs

Microbiology Exam 3 (8 decks)

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