Nematodes: Ascaris Lumbricoides

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Questions and Answers

During which stage can eosinophilia be found?

When the worms are in the abdomen

During adult worm migration

After the worms have been removed

During larval migration through the lungs (correct)

What type of imaging exam can help diagnose hepatobiliary or pancreatic ascariasis?

CT scan

MRI

Ultrasound (correct)

X-ray

What is ERCP used for in the diagnosis of ascariasis?

To diagnose intestinal blockage

To visualize the worms in the lungs

To extract the worm out of the patient (correct)

To visualize the worms in the abdomen

Which of the following is NOT a medication used to treat ascariasis?

Metronidazole Signup and view all the answers

Why is good sanitation important in preventing reinfection of ascariasis?

To prevent fecal contamination of soil Signup and view all the answers

What is the primary way that developing larvae are destroyed?

Sunlight and desiccation Signup and view all the answers

What is a way to reduce transmission of ascariasis in a community?

Mass treatment of children with single doses of mebendazole or albendazole Signup and view all the answers

What is the primary source of nutrition for the worms?

Semi-digested contents in the gut Signup and view all the answers

What is the primary symptom associated with larvae migration?

Cough and hemorrhagic pneumonia Signup and view all the answers

What is the role of eosinophils in the immune response?

Releasing granules on the worm's surface Signup and view all the answers

How do the worms enter the small intestine?

Through ingestion of raw foods Signup and view all the answers

What is the primary type of immune response involved in the infection?

Th2 immune response Signup and view all the answers

What is the primary way to diagnose the infection?

Stool microscopy Signup and view all the answers

What is the length of the adult female Ascaris lumbricoides?

45 cm Signup and view all the answers

What is the estimated number of people infected with Ascaris lumbricoides worldwide?

1 billion Signup and view all the answers

What is the fate of the worms in the small intestine?

They mature and mate, completing their life cycle Signup and view all the answers

How do Ascaris lumbricoides eggs mainly survive?

In warm, moist conditions Signup and view all the answers

What is the primary mode of transmission of Ascaris lumbricoides?

Ingestion of contaminated water or food Signup and view all the answers

What is the role of prior infection in Ascaris lumbricoides?

It has no effect on future infections Signup and view all the answers

What is the definitive host of Ascaris lumbricoides?

Humans or pigs Signup and view all the answers

How many eggs can a single female Ascaris lumbricoides produce daily?

200,000 Signup and view all the answers

How can Ascaris lumbricoides eggs be removed from water?

By filtration Signup and view all the answers

Study Notes

Nematoda: General Features

Ascaris lumbricoides is a common parasitic roundworm that infects humans, primarily in the intestines.
It is the largest nematode to infect humans, with adult females measuring up to 45 cm long.
An estimated 1 billion people are infected, with 25% of the world's population affected.

Host and Transmission

Definitive hosts: humans or pigs
No intermediate host
Transmission occurs mainly through ingestion of contaminated food or water, or inhalation of contaminated dust.
Children playing in contaminated soil can acquire the parasite from their hands.
Prior infection does not confer protective immunity.

Egg Characteristics

Eggs can survive for up to 10 years in warm, shaded, and moist conditions.
Eggs are resistant to chemical water purification methods, but can be removed by filtration and killed by boiling.
Developing larvae are destroyed by sunlight and desiccation.

Life Cycle

Females lay eggs in the small intestine, which are then passed out through feces.
Eggs develop into L1 larvae after 14 days, and L2 larvae after one week.
Ingestion of contaminated food or water leads to infection.
L2 larvae penetrate the intestinal wall, enter the portal blood stream, and migrate to the liver, heart, and lungs.
After several stages, the larvae mature and mate in the small intestine.

Food Habits

The parasite feeds on semi-digested contents in the gut.
It can also bite the intestinal mucus membrane and feed on blood and tissue fluids.

Symptoms

Larval migration can cause hemorrhagic pneumonia, cough, and breathing difficulties.
Adult parasites in the intestine can cause abdominal discomfort, nausea, and malnutrition.
In severe cases, the worm mass can block the intestine, leading to fatalities.

Host Immune Response

Innate immune response involves macrophages, neutrophils, and eosinophils.
Adaptive immune response involves a Th2 response with high IL-4 production, eosinophilia, and mastocytosis.

Diagnosis

Stool microscopy: eggs may be seen on direct examination of feces.
Eosinophilia: found during larval migration through the lungs.
Imaging: ultrasound or ERCP can detect worms in the abdomen or hepatobiliary/pancreatic ascariasis.

Treatment

Medications include mebendazole, albendazole, pyrantel pamoate, ivermectin, and piperazine citrate.

Prevention

Good sanitation is necessary to prevent fecal contamination of soil.
Limiting the use of human feces as fertilizer can help prevent infection.
Mass treatments of children with single doses of mebendazole or albendazole can reduce transmission.

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Description

Learn about Ascaris lumbricoides, a common parasitic roundworm found in human intestines, and its characteristics. Discover its impact on human health and the extent of its infection worldwide.