PathologyLesson 4 of 4 in the course Digestive System Infections

Transmission, Life Cycles, and Complications of GI Helminths

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Helminths are parasitic worms with varied body forms and life cycles. This lesson introduces the major helminth groups and explains how three important soil-transmitted nematodes infect people.

Many helminths are well adapted to humans, so infection can occur with few or no obvious symptoms. Others can cause serious intestinal or systemic disease.

All flashcards

What are the three major groups of helminths?
Nematodes are round-bodied worms, cestodes are segmented flatworms, and trematodes are non-segmented flatworms called flukes.
What is the migration route of *Ascaris lumbricoides*?
After eggs are ingested and larvae hatch, larvae penetrate tissue, travel through the circulation to the lungs, move to the pharynx, are swallowed, and return to the small intestine to mature.
How does hookworm reach the human intestine?
Larvae in contaminated soil penetrate skin, travel through the circulation to the lungs, are coughed up and swallowed, and then mature in the intestine.
What is cutaneous larva migrans?
It is an itchy skin condition caused by certain animal hookworm larvae migrating through human skin and leaving winding tracks.
What is *Strongyloides* autoinfection, and why is it important?
Larvae reinfect the same host by penetrating intestinal tissue or skin around the anus. Autoinfection can sustain chronic infection and may accelerate dangerously during immunosuppression.

Quiz questions

  1. Which body form characterizes nematodes?Answer: Round-bodied worms
  2. How do people commonly acquire ascariasis?Answer: By ingesting embryonated eggs in contaminated food or water.
  3. After reaching the lungs, what happens to *Ascaris* larvae before they mature in the intestine?Answer: They move toward the pharynx, are swallowed, and return to the small intestine.
  4. Why can hookworm infection cause anemia?Answer: Adult worms attach to the intestinal wall and feed on blood.
  5. Why can strongyloidiasis become life-threatening after glucocorticoid treatment?Answer: Immunosuppression can accelerate autoinfection and cause widespread larval migration.

Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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