M- Helminth Infections of the Gut Flashcards Preview

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Flashcards in M- Helminth Infections of the Gut Deck (55)
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How is enterobius vermicularus acquired?
What are features of its life cycle?
What organs are affected by adults?
What are the clinical features?
What is Dx?

1. Ingestion of eggs
2. develop in intestine, eggs deposit on perinal skin
3. colon
4. perianal pruritis
5. scotch tape test


Which 2 nematodes enter the human host via penetration of skin?

1. Strongyloides stercoralis
2. Hookworm (A. duodenale, N. americanus)


Which 3 nematodes have lung migration?

1. Strongyloides stercoralis
2. hookworms
3. ascaris lumbricoides


Which 2 nematodes preferentially affect the colon?

1. ponworm (e. vermicularis)
2. whipworm (trichuris trichiura)


Which nematode is associated with anemia?



What is the most common worm infection in the US?

pinworm (E. vermicularis)


A 10 year old comes to the office with perinanal itching. His mother says he hasn't been sleeping well and is quite irritable. He has experienced nausea and vomiting. Based on presentation, what do you think the child has?
What is the reservoir?
What is the mode of transmission?

Pinworm infection (E. vermicularis)

Reservoir: Humans (school age, preschool, mothers of children with pinworm)

1. ingestion of eggs by hand from anus to mouth
2. indirect via clothing, bedding, food


How is lab diagnosis made for enterobius?

1. Scotch tape test - examine for eggs in the morning before bathing or defacation

2. adult females on perianal skin at night with flashlight


What is the treatment for enterobius vermicularis?
How long should treatment be?

Treat the whole family with mebendazole and repeat the treatment in 2 weeks.


What is the largest human intestinal roundworm?

Ascaris lubricoides with adult works being 20-35cm long.
Eggs are 45-75 microns long


A pediatric patient is brought to your office because about a week ago, he began complaining about abdominal pain. It has been getting worse and he has progressed to having projectile vomiting. The abdomen was tense and tender with no stool in the rectal vault.
What nematode can present with these symptoms?
What could have been done a few weeks earlier to diagnose the problem before the child's intestines got obstructed?

How is this nematode treated?

It is consistent with Ascaris lubricoides because a serious side effect of an ascaris infection is bowel obstruction by a bolus of worms in children.

If you had done earlier lab tests, you could have identified eggs in feces by iodine wet mount or trichrome stain.

Treatment: albendazole


What group of people has the highest occurrence of ascaris lumbricoides infections?
What is the reservoir for this worm?
What is the mode of transmission?

It mostly affects recent immigrants from developing countries (usually children 3-8)

Reservoir: humans

Mode of transmission - ingesting infected eggs in soil contaminated with human feces (uncooked produce)


A woman from RGV presents with bloody/mucoid diarrhea. She has weight loss and weakness.
On physical exam you note abdominal tenderness and pain. She has rectal prolapse.
When you take a fecal sample, you note barrel-shaped eggs with bipolar opercula. What is the organism?
Where does it reside in humans?

This is trichuris trichiura (whipworm)

The whipworm resides in the colon of the human.


What population is most affected by whipworm?
What is the reservoir?
What is the mode of transmission?

Trichuris trichiura is prevalent in the south with warm, humid climate.
It affects mostly children and institutionalized mentally retarded.

Reservoir: humans

Mode of Transmission: ingestion of eggs from fecally contaminated soil


What is diagnostic for whipworm?
What is treatment ?

Diagnosis: barrel-shaped eggs with bipolar opercula

Treatment: albendazole


HTLV-1 predisposes to an infection by what helminth?

strongyloides stercoralis


What is unique about the life cycle of strongyloides stercoralis?

It can exist free-living in the soil OR in the small intestine of a host


An immunocompromised man presents with the following symptoms:
1. GI - ulceration, sloughing of mucosa
2. Pulm - coughing, infiltrate, Loeffler's
3. urticarial rash in trunk, buttocks, waist (larva currens)

Lab work shows an elevated IgE and blood eosinophilia.

What is the likely cause?
What is treatment?

Strongyloides starcoralis - Ivermectin


What is the pathogenesis of strongyloides starcoralis?

1. filariform larvae penetrate skin of host
2. Go to lungs-->alveoli--> coughed up and swallowed
3. In small intestine larvae molts x2 to become adult female

Hyperinfection (due to large passage of worms through the lungs) and
Autoinfection - dissemination of larvae to other body parts


What is laboratory diagnosis of S. starcolaris?
What is treatment?

1. rhabditiform larvae in ova¶site examination of stool [rarely if EVER see eggs]



What are the 2 human hookworm species?
What is the difference in their "hooks"?
What is the purpose of the hooks?

N. americanus - cutting plates
A. duodenale- teeth

The purpose of the hooks is to penetrate the intestinal mucosa.


A child presents with iron deficient anemia. He is small for his age and is malnourished.
He has been having epigastric pain and diarrhea (sometimes bloody/mucousy). He has pruritis on the bottom of his foot.
What is the likely worm?
Why does he have anemia?
What is causing the itching?

It is likely hookworm.
The Fe deficient anemia is due to blood loss at the site of intestinal attachment and is the most common symptom of hookworms

The pruritis is called "ground itch" and occurs at the site of penetration of the filariform larvae.


What is the pathogenesis of hookworm?

1. infective larvae (filariform) penetrate skin and are carried through blood to the lungs
2. coughed up, swallowed--> small intestine
3. In small intestine it matures to adult worm
4. adult worm lays eggs that hatch to rhabditiform larvae that are passed in fecal matter


In hookworms, there is elevated serum IgE and eosinophilia just like in ___________________. What is the difference between these two organisms?

Both hookworms and strongyloides have elevated serum IgE and eosinophils.

Strongyloides - autoinfection, reinfection, dissemination

Hookworms - no autoinfection or dissemination


What is lab diagnosis of hookworm?
What is treatment?

Diagnosis: ova¶site of the stool
Eggs cannot distinguish btwn n. americanus and a. duodenale.

Treatment: albendazole


How is Taenia saginata acquired?
What is the location in man?
How is it diagnosed?

T. saginata is acquired by ingesting undercooked beef.
It is located in the adult small intestine

Dx: proglottids in feces with over 15 branches


How is Taenia solium acquired?
What is the location in man?
How is it diagnosed?

T. solium is acquired by ingesting undercooked pork.
The adult form is in the adult small intestine.

Dx: proglottids in the feces with under 12 branches


How are the larvae of taenia solium acquired?
What is the location in man?
How is it diagnosed?

It is acquired by ingesting eggs from the environment or hands of infected individuals.

Cysticerci (larvae) are located in the muscle, brain and eyes

Dx: imaging (CT, MRI), serological tests


How are ecchinococcus granulosus acquired? What is the location in man?
How is diagnosis made?

Acquired via the ingestion of dog feces

Larvae are located in liver, lung, brain

Dx: serological and skin tests, cyst fluid (hydatid sand) in the operating room


How is diphyllobothrum latum acquired? What are clinical findings?

Acquired by ingesting fish.
Clinical findings - short and wide proglottids