Deck 50: Intestinal Nematodes Roundworms

Question 1

The most common and largest roundworm encountered is:

A) Trichuris trichiura.
B) Strongyloides stercoralis.
C) Ascaris lumbricoides.
D) Necator americanus.

Answer 1

C
A.lumbricoides is the most common and the largest roundworm.The parasite has a worldwide distribution with higher prevalence in the tropical regions.

Question 2

The eggs of the Ascaris lumbricoides worm are ingested and hatched in the duodenum, penetrate the intestinal wall, and migrate to the hepatic portal circulation.Its geographic distribution and infection rate are associated with:

A) institutional crowding.
B) poor sanitation.
C) day care centers.
D) moist warm soil.

Answer 2

B
The eggs of the organism A.lumbricoides are ingested and hatch in the duodenum, penetrate the intestinal wall, and migrate to the hepatic portal circulation.The adult worms live and reproduce in the lumen of the small intestine.Geographic distribution is associated with climate and poor sanitation.

Question 3

Löffler syndrome is associated with which roundworm infection?

A) Strongyloides stercoralis
B) Ancylostoma duodenale
C) Trichostrongylus spp.
D) Ascaris lumbricoides

Answer 3

D
Many A.lumbricoides infections are asymptomatic.The presentation of symptoms correlates with the length of infection, the number of worms present, and the overall health of the host.Intestinal symptoms range from mild-to-severe intestinal obstruction.Some patients develop pulmonary symptoms and with immune-mediated hypersensitivity pneumonia.The worms may cause an immune condition known as Löffler syndrome characterized by peripheral eosinophilia.

Question 4

Direct penetration of which of the following worms results in tissue damage at the site of attachment, blood loss, and an acute gastrointestinal phase demonstrated by an increased eosinophilia?

A) Whipworm
B) Pinworm
C) Threadworm
D) Hookworm

Question 5

The larvae of the worm Strongyloides stercoralis are the most common found in human stool specimens.Depending on the fecal transit time through the intestine and the patient's condition, both rhabditiform and rare filariform may be present.The treatment of choice for uncomplicated infections is:

A) metronidazole.
B) ivermectin.
C) pyrantel pamoate.
D) combination antihelminthic and board-spectrum antibiotics.

Question 6

Rhabditiform larvae measuring 275 mmicrons with a long buccal capsule and a small genital primordium was identified as hookworm.Which one of the following statements explains this discrepancy?

A) A technical error occurred in identification.
B) The larvae characteristics represent Strongyloides stercoralis; therefore the organism was incorrectly reported out.
C) The larvae characteristics represent pinworm; therefore the organism was incorrectly reported out.
D) No error occurred. Hookworm is the correct identification for an organism with these characteristics.

Question 7

A 36-year-old man entered the emergency department with bleeding and weight loss several weeks after returning from a trip to South America.A stool sample was taken and microscopically examined.Barrel-shaped eggs with bipolar plugs were observed.The organism can be identified as:

A) Trichuris trichiura.
B) Ancylostoma duodenale.
C) Necator americanus.
D) Strongyloides stercoralis.

Question 8

A 4-year-old boy attended day care 3 days per week.He was irritable, and his parents noticed that he had persistent perianal itching.A sticky paddle was pressed against the perianal region and sent to the laboratory for testing.The eggs microscopically observed would most likely have which one of the following morphologic features?

A) Long with a short buccal cavity
B) Thin shell with internal granules
C) Bipolar plugs
D) Flat-sided, football-shaped

Question 9

The infective larvae of the parasite Strongyloides stercoralis penetrate the skin and migrate through the circulatory system to the heart and lungs.The organism enters the bronchial tree and is then swallowed, entering the digestive tract, where the organism matures into an adult worm.This parasite is classified as which type of infection?

A) Pinworm
B) Threadworm
C) Whipworm
D) Hookworm

Question 10

A short buccal capsule, large bulb on the esophagus, and prominent genital primordium are all characteristics of which worm?

A) Trichuris trichiura
B) Capillaria philippinensis
C) Strongyloides stercoralis
D) Ascaris lumbricoides