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Intestinal nematodes


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What are two ways that pinworm can be diagnosed?
1. Scotch tape on perianal skin
2. Eggs present in stool
In what patient population are pinworms most common? Why?
*poor hygeine, low immunity
How is pinworm treated?
*household cleaning to get rid of eggs
How is pinworm acquired? Where in the body does it live? How large is the adult?
*Eggs are ingested
*In the large intestine
*1 cm
What symptoms are seen with infection by Ascaris?
*usually asymptomatic
*high worm burden may result in pneumonitis or obstructive disorders
Ascaris passes eggs in the stool of its host.
True - this is often a means of diagnosis.
Ascaris can be transmitted by fecal-oral contact.
False: the eggs require a period of embryonation in warm, most soil before they may become infective.
Describe the life cycle of Ascaris once the embryonated eggs have been ingested.
1. Eggs hatch, larvae penetrate GI mucosa
2. Larvae travel to lung tissue and undergo two molt changes
3. Larvae penetrate alveoli and are coughed up and swallowed
4. Larvae mature into adults in the gut
How does Ascaris attach to the intestinal wall?
It does not attach to the wall and must move constantly to maintain position.
How big are adult hookworms?
What is the pathogenic nature of the hookworm?
*abrades the intestinal lining to obtain a blood meal
*blood loss causes anemia, thrombocytopenia, leukopenia
How is a hookworm infection acquired?
*eggs hatch on the ground
*larvae penetrate unbroken skin and enter bloodstream
*worms migrate to lungs and penetrate alveoli
*worms are coughed up and swallowed to inhabit the gut
What is "ground itch"?
A hypersensitivity reaction caused when a hookworm penetrates unbroken skin.
How is a strongyloides infection acquired?
*larvae penetrate unbroken skin
*organ donation
Where do the larvae of Strongyloides hatch and mature?
*eggs hatch in the intestine
*larvae pass in stool and mature in the soil
How does auto re-infection with strongyloides occur?
*larvae mature in intestine or on perianal skin
What is larva currens?
When the larvae of strongyloides migrate to the skin and cause itching.
How does immunosuppression affect a latent infection with strongyloides?
It can cause a hyerinfection that can include strongyloides pneumonia and be life-threatening.
Strongyloides are able to pass their life cycle in the soil outside of the host.
What happens in a larva migrans infection?
*humans are infected by species-specific round worm larvae
*larvae are unable to complete their life cycle
*fibrotic lesions form around the larvae
Name four varieties of larva migrans and their site of infection.
1. Visceral: liver
2. Ocular: retina
3. Neuro: brain
4. Cutaneous: skin
What type of worm is typically responsible for larva migrans infection?
*dog/cat ascaris
*dog/cat hookworm has been known to cause cutaneous larva migrans

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