Ascaris lumbricoides (E8, Week 14) Flashcards

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Questions and Answers

What class of microorganisms is Ascaris lumbricoides part of?

Nematodes (roundworms)

What group of nematodes is Ascaris lumbricoides?

GI nematodes 'HEATS'

Ascaris lumbricoides is AKA?

Giant roundworm

What makes a definitive host in parasitic infection?

Sexual reproduction of the parasites Signup and view all the answers

What is the appearance of the eggs of Ascaris lumbricoides?

Bumpy edged eggs, 'Crenelated', 'Mammilated' Signup and view all the answers

What is the appearance of the adult form of Ascaris lumbricoides?

Earthworm with sharper heads Signup and view all the answers

What is the transmission of Ascaris lumbricoides?

Fecal-Soil-Oral transmission Signup and view all the answers

Describe the life cycle of Ascaris lumbricoides?

<ol> <li>Eggs in feces must mature in soil for 1-2 weeks. 2. Contaminated foods or hands --> ingestion of egg. 3. Egg hatches into worm in GI. 4. Worm burrows out bowel wall into venous system. 5. Worm enters heart then lungs --> pneumonitis. 6. Cough and swallowed back into GI tract --> maturation. 7. Female parasite generates eggs that go into stool.</li> </ol> Signup and view all the answers

What locations in the world is Ascaris lumbricoides typically found?

Tropics with poor sanitation Signup and view all the answers

How many humans are infected with Ascaris lumbricoides?

25% worldwide Signup and view all the answers

What are the phases of illness with Ascaris lumbricoides infection?

Early and Late Signup and view all the answers

How does early illness with Ascaris lumbricoides present?

Asymptomatic or eosinophilic pneumonitis Signup and view all the answers

What is eosinophilic pneumonitis in Ascaris lumbricoides infection?

IgE-mediated immune response to larvae in lungs Signup and view all the answers

What is the clinical presentation of eosinophilic pneumonitis in Ascaris lumbricoides infection?

Cough, wheezing, chest pain, hemoptysis Signup and view all the answers

What are the imaging findings of eosinophilic pneumonitis in Ascaris lumbricoides infection? What does it mimic?

Lobar infiltrate on CXR; may mimic bronchopneumonia Signup and view all the answers

What are the sputum findings of eosinophilic pneumonitis in Ascaris lumbricoides infection?

Eosinophils, Charcot-Leyden crystals Signup and view all the answers

What is eosinophilic pneumonitis AKA?

Loeffler's syndrome Signup and view all the answers

How does late illness with Ascaris lumbricoides present?

Often asymptomatic or nausea, abdominal pain, diarrhea Signup and view all the answers

What are serious complications of Ascaris lumbricoides?

Bowel blockage, ectopic adults = migration: 1. Up biliary tree --> pancreatitis, biliary sepsis 2. Into peritoneum (peritonitis) 3. Other sites Signup and view all the answers

How is Ascaris lumbricoides diagnosed?

<ol> <li>Fecal 'Ova & Parasite' prep 2. Colonoscopy 3. Ultrasound 4. GI series (X-ray after swallowing barium)</li> </ol> Signup and view all the answers

What is the treatment for Ascaris lumbricoides?

'Bendazoles' (Albendazole, Mebendazole), Pyrantel Signup and view all the answers

Study Notes

Overview of Ascaris lumbricoides

Belongs to the class of nematodes, commonly referred to as roundworms.
Classified as gastrointestinal (GI) nematodes, often described using the mnemonic "HEATS."

Common Names and Host Information

Also known as the giant roundworm.
Definitive hosts are characterized by the sexual reproduction of parasites.

Egg and Adult Morphology

Eggs have a distinct appearance: bumpy edges, termed "crenelated" and "mammilated."
Adult form resembles an earthworm but features sharper heads.

Transmission and Life Cycle

Transmitted through fecal-soil-oral routes.
Life cycle involves:
- Eggs mature in soil for 1-2 weeks post-feces.
- Ingestion occurs via contaminated food or hands.
- Eggs hatch in the gastrointestinal tract, allowing worms to burrow into the venous system.
- Worms migrate to the heart and lungs, causing pneumonitis.
- Eventually, larvae are coughed up, swallowed, and mature in the GI tract, leading to egg production expelled in stool.

Geographic Distribution and Prevalence

Typically found in tropical regions with poor sanitation.
Approximately 25% of the global population is infected.

Phases of Illness

Infections present in two phases: early and late.
Early illness can be asymptomatic or show eosinophilic pneumonitis.

Eosinophilic Pneumonitis Details

An immune response mediated by IgE occurs due to larvae in the lungs, known as Eosinophilic pneumonitis.
Clinical presentation may include cough, wheezing, chest pain, and hemoptysis.
Imaging findings may show lobar infiltrates on chest X-ray, potentially mimicking bronchopneumonia.
Sputum analysis reveals the presence of eosinophils and Charcot-Leyden crystals.
This condition is also referred to as Loeffler's syndrome.

Late Illness Presentation

Often presents as asymptomatic or with symptoms such as nausea, abdominal pain, and diarrhea.

Complications

Serious complications include bowel blockage and the migration of adult worms to ectopic sites, which can cause:
- Up the biliary tree leading to pancreatitis and biliary sepsis.
- Peritoneal migration resulting in peritonitis.
- Migration to other organ sites.

Diagnosis and Treatment

Diagnosis methods include:
- Fecal examination for ova and parasites.
- Colonoscopy.
- Ultrasound imaging.
- GI series with barium swallow.
Treatment options include benzimidazoles like albendazole and mebendazole, and pyrantel.

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Test your knowledge about Ascaris lumbricoides with these flashcards. Learn about its classification, characteristics, and the role of definitive hosts in parasitic infections. Perfect for students studying microbiology or parasitology.