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Microbiology > Exam #5: GI Helminths > Flashcards

Exam #5: GI Helminths Flashcards

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Biology 101 flashcards
1
Q

What are nematodes? What are the general characteristics of roundworms?

A

Roundworms

  • Cylindrical shaped (ala round worms)
  • Non-segmented
  • Separate sexes
  • Complete digestive system
  • Covered in a protective cuticle

*Note that you need to be infected by BOTH sexes to have infection

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2
Q

How are helminth infections diagnosed?

A

Egg morphology

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3
Q

Where are helminth infections most common in the US & why?

A
  • Southeastern US

- Climate is best for egg growth

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4
Q

What does it mean that “adult worms do NOT replicate in man?”

A
  • Adult worms have “sex” in the intestines & you shed the eggs
  • However, the number of adults will NOT increase
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5
Q

What eosinophila an indication of?

A

Helminth infections i.e. Nematode infection that has passed to other tissues from the GI tract

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6
Q

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

A

Enterobius vermincularis (pinworm)

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7
Q

What are Geohelminths?

A

Nematode infections acquired through contact with infected soil

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8
Q

What is Enterobius vermincularis? What are the characteristic egg shape? What is enterobiasis?

A

Enterobiasis is the name of the disease caused by Enterobius vermincularis, or the pinworm.

  • Pinworm
  • Eggs are flat on one side

*This is the most common helminth infection in the US.

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9
Q

Describe the lifecycle of Enterobius vermincularis.

A
  • Infected individual sheds eggs into environment
  • Another individual ingests eggs
  • Eggs hatch in the small intestine & then travel to the large intestine, where they mature
  • Adult forms mate in the large intestine
  • At night females come out of the rectum & lay eggs

*Note that some eggs can become airborne

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10
Q

What is the mode of transmission for Enterobius vermincularis?

A
  • Fecal-oral
  • Children most commonly self-infect by ingestion after scratching the anal or perianal region

*Note that reinfection & transmission to family is common. Also, the pinworms of other animals e.g. dogs, do NOT transmit to humans

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11
Q

What are the symptoms of Enterobius vermincularis infection?

A
  • Typically asymptomatic

- Perianal itching (Pruritus)

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12
Q

How are Enterobius vermincularis infections diagnosed?

A

“Scotch tape test”

  • Identification of eggs in perianal region
  • Eggs are flatter on one side than the other

*Sometimes adult worms can be seen in the perianal region at night

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13
Q

How is Enterobius vermincularis infection treated?

A

Treatment is with several anti-helminthic compounds (mebendazole, pyrantel pamoate)–usually a single dose followed by another dose 2 weeks later

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14
Q

List the “Geohelminths.” How are these helminths commonly separated?

A

Ingestion of infectious eggs found in soil:

  • Ascaris
  • Trichuris

Active penetration of the skin:

  • Strongyloides
  • Hookworms
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15
Q

What is Trichuriasis? What causes Trichuriasis?

A

Trichuriasis is more commonly referred to as whipworm infection. Specifically, the causative organism is Trichuris trichuria.

*Name comes from the shape of the large female worm

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16
Q

Describe the life cycle of Trichuris trichiura.

A
  • Eggs are excreted out of an infected individual
  • Contamination of soil with infective eggs
  • Ingestion from soil
  • Eggs hatch in the small intestine & mature
  • Travel to large intestine & attach/ reproduce to make more eggs
17
Q

Where is Trichuris trichiura commonly seen in the US?

A

Mostly seen in the tropics, but can be found in the southeast US

18
Q

How is Trichuris trichiura transmitted?

A

Fecal-oral (contaminated soil)

19
Q

What are the symptoms of Trichuris trichiura infection?

A

90% are asymptomatic; however, in symptomatic patients:

  • Bloody, mucus containing diarrhea
  • Frequent stool
  • Tenesmus (urge to defecate) in absence of stool
  • Rectal prolapse
  • May contribute to growth retardation & anemia

*One of the most frequently identified causes of recurrent rectal prolapse & children with high worm loads can appear emaciated & anemic

20
Q

How is Trichuris trichiura diagnosed?

A

Identification of eggs in stool that are:

  • Thick walled
  • Barrel shaped with plugs at each end
21
Q

What is Ascaris lumbricoides? What does Ascaris lumbricoides cause?

A
  • Ascaris lumbricoides causes Ascariasis

- Largest nematode infection (foot long & diameter of a pencil)

22
Q

Describe the lifecycle of Ascaris lumbricoides.

A
  • Ingested eggs hatch & molt in the small intestine (like other nematode infections)
  • However, larvae penetrate the intestine & enter the bloodstream
  • From the bloodstream, larvae invade the lung alveoli
  • Larvae then “crawl” up the trachea to the glottis & are swallowed
  • Larvae then travel back to the small intestine where they mature into adults
23
Q

Ascaris lumbricoides is associated with migration out of the GI tract. How does this manifest?

A

Eosinophilia

24
Q

What are the symptoms caused by Ascaris lumbricoides infection? What are the clinical manifestations of intestinal & pulmonary infection?

A

Most are asymptomatic; however, symptoms can range from abdominal discomfort to death:

Intestinal symptoms are due to physical presence

  • Abdominal pain
  • dyspepsia
  • appetite loss
  • vomiting
  • diarrhea

Pulmonary symptoms

  • Mild cough
  • Pneumonitis resembling asthma attack
25
Q

How are Ascaris lumbricoides infections transmitted?

A

Fecal-oral; soil contaminated with human feces

26
Q

How is Ascaris lumbricoides infection diagnosed?

A

GI= eggs in stool that are oval with a bumpy surface
Pulmonary=
- Observation of larvae in sputum
- Eosinophils in sputum

27
Q

What causes Hookworm infections? Where are these organisms most endemic?

A
  • Necator americaus (Southeastern US)

- Ancylostoma duodenale (Tropics)

28
Q

Describe the lifecycle of the Hookworms.

A
  • Eggs hatch in soil, releasing larvae
  • Larvae in soil mature and become infectious forms (filariform)
  • Can attach to skin & penetrate into the tissue, or enter via hair follicle
  • Larvae migrate through the lymphatics to the bloodstream
  • From the bloodstream they travel to the alveoli
  • Like Ascaris they then ascend the trachea & are eventually swallowed, leading them to the small intestine
  • Production of eggs occurs in the small intestine

Worms consume blood!

29
Q

What can Hookworm infection cause?

A

Anemia (consumption of blood)

*Note that this is particularly concerning in children & pregnant women

30
Q

Can dog and cat hookworms can infect humans?

A

Yes, but they do not have the systemic effects that human hookworms do.

Rather, they cause “Cutaneous larval migrans”

31
Q

What are the clinical manifestations of Hookworm infection?

A
  • Iron-deficiency anemia
  • Protein malnourishment
  • Moderate dermaitis
  • Pneumonia
  • Eosinophila
32
Q

What does Strongyloides stercoralis cause?

A

Strongyloidasis

33
Q

What is unique about Strongyloides stercoralis ?

A

Facultative–can replicate in the host & in the environmentally, independently

  • Larvae shed
  • Replication in the soil
  • Smallest
34
Q

Describe the lifecycle of Strongyloides stercoralis .

A

Same as hookworms for parasitic infection, except there are NO MALES, ONLY FEMALES!

35
Q

What are the symptoms of Strongyloides stercoralis infection?

A
  • Little worm burden= little symptoms

- Pulmonary stage may provoke pulmonary inflammation & eosinophilia

36
Q

When is Strongyloides stercoralis hyper-infection most commonly seen?

A

Immunosuppressive therapy (glucocorticoides)

37
Q

What are the symptoms of Strongyloides stercoralis hyperinfection & disseminated infection?

A

Hyper-infection= worsening of pulmonary & GI symptoms

Disseminated infection= CNS, peritoneum, liver, & renal infection

Microbiology (49 decks)

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