M- Helminth Infections of the Gut Flashcards Preview

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Flashcards in M- Helminth Infections of the Gut Deck (55):

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


What are the anatomical parts of an adult Taenia worm?

What is meant by a gravid worm?

1. scolex - suckers and grooves
2. neck
3. proglottids - male/female reproductive parts

Gravid worms contain eggs in the uterus


Describe the larvae of taenia.

Cysticercus = cystic structure with inverted scolex and fluid


Between taenia solium and taenia saginata, which is more frequently symptomatic?

Saginata- mild abdominal symptoms with active AND passive passage of proglottids.

Taenia solium is less frequently symptomatic with the only symptoms being passive passage of proglottids


Which strain of Taenia is associated with cysticercosis?

Solium - the ingestion of eggs can lead to larval cysts in muscle and the brain.


What is the mode of transmission of T. saginata? T. solium?

T saginata is passed in the stool of an infected person. This stool is infectious to COWS ONLY. The next human gets infected by eating beef with cysticeri in it.

T solium is passed in the stool of an infected person. Humans get it again by eating undercooked/measly pork. Cystecercosis is from ingesting ova.


A patient presents with subcutaneous cysts. They are complaining of blurry vision.
They recently began getting seizures.
What are you suspicious of?

Cysticercosis due to the ingestion of taenia solium ova.

This tends to affect:
1. subcutanous
2. Ocular
3. CNS


How does one make a laboratory diagnosis of cysticercosis?

1. CT and MRI scans for cysts
2. serology for IgG to T. solium


What is treatment for cysticercosis?

asymptomatic cysts and easily controlled seizures do not require treatment.
- anti-inflammatories


Describe the structure of echinococcus granulosus.
How long is the worm?
Where do adult worms reside?
How many proglottids?

It is 3-6 mm long and resides in the small intestine of dogs or other canids.

The adult worm is small with 3 proglottids


Where do hydatid cysts most frequently develop?
What causes the symptoms?
If the cyst ruptures, what will happen?

They most frequently occur in the liver
[but also lungs, brain, kidney, spleen, bone, heart]

Symptoms occur because of:
1. space occupying mass
2. rupture --> severe allergic rxn/ anaphylaxis

Cysts can be secondarily infected with bacteria and older cyst can calcify.


What is the mode of transmission of echinococcos granulosos?

Infection in humans is acquired by accidental ingestion of eggs of the parasite from the dog.
1. dog feces contaminating environment
2. dog fur


What are the 3 tests/findings that are useful for diagnosing echinococcus granulosos?

1. CT/MRI/ultrasound to see the cyst
2. serological tests
3. presence of hydatid sand [protoscolices and hooks of protoscolices] at operation


What is the most common treatment for echinococcus granulosos?

1. surgery
2. albendazole to ensure there isnt recurrence


What is the geographic distribution of S. mansoni?
Where do adults live?
Where in the host are eggs deposited?

Africa, Middle East, Caribbean, S. America

The adult schistosomes live in the IMV.
Eggs get deposited in the rectum/colon


What is the geographic distribution of S. japonicum?
Where do adults live?
Where in the host are eggs deposited?

China, Phillipines, Japan

Adult schistosomes live in the SMV.
Eggs are deposited in the small intestine


What is the geographic distribution of S. hematobium?
Where do the adult schistosomes live?
Where in the host are eggs deposited?

Africa, Middle East
The adults live in the venous plexus near the urinary bladder.
Eggs are deposited in the urinary bladder


A patient from Africa presents with a rash, pulmonary infiltrate and portal hypertension causing hepatomegaly and splenomegaly.
What strain of schistosome is most likely at fault?

How would you diagnose?

S. mansoni

1. eggs in stool
2. rectal biopsy/scraping
3. serology


A patient presents with a rash, pulm. infiltrate, and portal hypertension with hepatomegaly and splenomegaly. They are starting to display neurologic symptoms and develop pulmonary hypertension/cor pulmonale. What strain of schistosome is most likely at fault?

What is diagnosis?

S. japonicum

1. eggs in stool
2. retal biopsy
3. serology


A patient presents with hematuria, dysuria, pyuria, and blood clots in the urine. What strain of schistosome is most likely at fault?
What are they at risk to develop?
What is diagnosis?

S. hematobium and they are at risk for bladder carcinoma

1. eggs in URINE
2. cystoscopy
3. bladder biopsy
4. serology


Describe the eggs of schistosomes.

1. non-percolate

2. possess a spine [terminal on hematobium, lateral on mansoni, japonicum]

3. miracidium- ciliated larva that hatches from schistosome egg and enters snail


Describe the pathogenesis of schistosomes.

1. eggs released from feces or urine
2. hatch to miracidia--> infect snail
3. 2 generations of sporocysts and make cercariae
4. cercariae are released from snail and penetrate the skin of human hosts
5. in the host it becomes schistosomulae--> veins


Describe the pathogenesis of acute schistosomiasis. (Katayama's fever).
What are the symptoms?
When does it occur after infection?
What happens if there is continuing infection?

fever, cough, ab pain, diarrhea, hepatosplenomegaly, eosinophilia

(serum sickness like illness due to the high worm and egg antigen stimuli. It occurs with the first egg laying 4-6 wks after infection )

If there is continuing infection-->granulomatous reactions and fibrosis.


What are cecarciae and schistosomula?

Cecariae - penetrates the skin --> allergic dermatitis at the site. If prior sensitation --> papular rash

Schistosomula - tailless cecariae that go through blood and lymphatics to the right side of heart and lungs (cough, fever, eosinophilia)


What causes Katayama fever and schistosomiasis?

The eggs are responsible for the pathology of schistosomes. The adult worms are very rarely pathogenic.

Katayama - high worm and egg antigen stimuli leads to immune complex formation and serum sickness-like illness

Schistosomiasis- immunological reaction to eggs in tissue that leads to a granulamatous reaction (T cells, macrophages, eosinophils)


What is diagnosis and treatment for schistosomiasis?

1. eggs in stool or urine
2. serology for Katamaya fever