Podcast
Questions and Answers
Why is auto-infection a significant factor in the transmission cycle of Enterobius vermicularis?
Why is auto-infection a significant factor in the transmission cycle of Enterobius vermicularis?
- Because the eggs deposited in the perianal region cause intense itching, leading to scratching and subsequent transfer of eggs to the mouth. (correct)
- Because the filariform larvae can penetrate intact skin, initiating a new cycle of infection within the host.
- Because the adult worms migrate from the colon to the small intestine, releasing eggs that are then re-ingested.
- Because the parasite directly penetrates the intestinal wall, releasing eggs into the bloodstream for systemic distribution.
Which of the following best describes the unique reproductive strategy employed by female Strongyloides stercoralis worms?
Which of the following best describes the unique reproductive strategy employed by female Strongyloides stercoralis worms?
- Parthenogenesis, where female worms produce eggs that develop into larvae without fertilization. (correct)
- Hermaphroditic reproduction, where a single worm can produce both eggs and sperm.
- Asexual reproduction via binary fission within the intestinal submucosa.
- Sexual reproduction requiring both male and female worms within the host.
What is the primary mechanism by which filariform larvae of Strongyloides stercoralis initiate infection in humans?
What is the primary mechanism by which filariform larvae of Strongyloides stercoralis initiate infection in humans?
- Ingestion of contaminated food or water containing the larvae.
- Direct penetration of the skin by larvae present in contaminated soil. (correct)
- Inhalation of aerosolized larvae from contaminated soil.
- Transmission through the bite of an infected arthropod vector.
How does the life cycle of Strongyloides stercoralis increase the risk of hyperinfection syndrome in immunocompromised individuals?
How does the life cycle of Strongyloides stercoralis increase the risk of hyperinfection syndrome in immunocompromised individuals?
Why is the 'scotch tape test' specifically useful in diagnosing Enterobius vermicularis infections?
Why is the 'scotch tape test' specifically useful in diagnosing Enterobius vermicularis infections?
Which of the following is the most critical factor contributing to the differing clinical manifestations observed between Enterobius vermicularis and Strongyloides stercoralis infections?
Which of the following is the most critical factor contributing to the differing clinical manifestations observed between Enterobius vermicularis and Strongyloides stercoralis infections?
A patient is diagnosed with strongyloidiasis. What aspect of the Strongyloides stercoralis life cycle makes it necessary to consider a longer treatment duration, especially in immunocompromised individuals?
A patient is diagnosed with strongyloidiasis. What aspect of the Strongyloides stercoralis life cycle makes it necessary to consider a longer treatment duration, especially in immunocompromised individuals?
How would you distinguish a Strongyloides stercoralis infection from an Enterobius vermicularis infection based solely on microscopic examination of stool samples?
How would you distinguish a Strongyloides stercoralis infection from an Enterobius vermicularis infection based solely on microscopic examination of stool samples?
If a patient presents with perianal pruritus and a suspected Enterobius vermicularis infection, but initial 'scotch tape' tests are negative, what further diagnostic steps should be considered?
If a patient presents with perianal pruritus and a suspected Enterobius vermicularis infection, but initial 'scotch tape' tests are negative, what further diagnostic steps should be considered?
Why might treatment with corticosteroids increase the risk of disseminated strongyloidiasis?
Why might treatment with corticosteroids increase the risk of disseminated strongyloidiasis?
Flashcards
Enterobius vermicularis
Enterobius vermicularis
Commonly known as pinworm, infects humans exclusively, residing in the cecum, appendix, and ascending colon. Transmission occurs via contaminated fingers and auto-infection, especially in children.
Enterobius vermicularis Infection
Enterobius vermicularis Infection
Infection occurs through self-inoculation, transferring eggs from perianal area to the mouth via contaminated hands, or through contaminated surfaces.
Nocturnal Migration
Nocturnal Migration
Adult females migrate nocturnally outside the anus to lay eggs on the skin, causing intense perianal itching.
Strongyloides stercoralis
Strongyloides stercoralis
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Strongyloides Transmission
Strongyloides Transmission
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Strongyloides Diagnosis
Strongyloides Diagnosis
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Strongyloides Life Cycle
Strongyloides Life Cycle
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Enterobiasis Detection & Treatment
Enterobiasis Detection & Treatment
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Study Notes
- Two nematodes: Enterobius vermicularis and Strongyloides stercoralis.
Enterobius Vermicularis (Pinworm)
- Humans are the only host.
- Exists in two stages: adult worms and eggs.
- Found in the cecum, appendix, and adjacent ascending colon.
- Transmission: contaminated fingers and auto-infection, commonly in children.
- Causes perianal itching or pruritus due to worms and eggs in the perianal area.
- Diagnosed by observing eggs via the Scotch tape technique under a microscope or seeing adult worms in diapers.
- Eggs are elongated, thick-walled, and slightly flattened at one end.
- Mebendazole is an effective treatment.
Enterobius Vermicularis Life Cycle
- Gravid adult female pinworms deposit eggs on perianal folds.
- Infection occurs through self-inoculation, such as transferring eggs to the mouth via contaminated hands.
- Eggs can be exposed via contaminated surfaces and clothing.
- Upon ingestion, larvae hatch in the small intestine, and adults establish in the colon, especially the cecum.
- The time from ingestion to new egg-laying is about one month.
- Adult females measure 8-13 mm; males measure 2-5 mm.
- Adult lifespan is about 2 months.
- Gravid females migrate nocturnally outside the anus to lay eggs on the perianal skin, causing perianal pruritus.
- Larvae inside eggs develop in 4-6 hours under optimal conditions and become infective.
Strongyloides Stercoralis (Threadworm)
- Humans and dogs are the hosts.
- Exists in three stages: adult worms, eggs, and filariform larvae.
- Found in the small intestine, especially the duodenum and jejunum.
- Transmission: filariform larvae in contaminated soil penetrate the skin.
- Infection is often asymptomatic but may cause cutaneous, pulmonary, and intestinal manifestations, especially in immunocompromised individuals.
- Diagnosed by observing eggs, larvae, or adult forms in the stool.
- Often associated with eosinophilia.
- Ivermectin or thiabendazole are treatments for strongyloidiasis.
Strongyloides Stercoralis Life Cycle
- Filariform larvae in contaminated soil penetrate human skin via enzymes.
- Larvae migrate to the intestine through abdominal viscera or connective tissue.
- In the small intestine, larvae molt twice and become adult worms.
- Female adult worms embed in the submucosa of the small intestine and produce eggs through parthenogenesis (no parasitic males).
- Eggs hatch into rhabditiform larvae, which can be passed in the stool or cause auto-infection.
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