<B>Ascariasis </B>

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Ascariasis

Etiology:

• Ascaris lumbricoides is an intestinal roundworm.

Pathogenesis:

• Infection occurs by ingestion of embryonated eggs either in fluids or food.
• The larvae emerge in the duodenum and migrate to the lungs via the portal circulation.
• About two weeks after ingestion symptoms of pneumitis develop with fever, sputum production and radiographic infiltrates.
• The larvae migrate through the alveoli in the bronchopulmonary tree, and arrive in the pharynxwhere they are swallowed.
• The larvae arrive in the small intestine where development into mature worms occur.

Epidemiology:

• Ascaris lumbricoides has a worldwide distribution.
• Infection rates are particularly high in warm humid tropical regions.

General Gross Description:

• Ascaris is a large roundworm more than 20 cm. in length.
• They are seen most commonly in the small intestine, or secondarily in the appendis. Rarely they migrate to the bile ducts.
• Multiple worms may be seen and these can cause obstructing balls.
• The worms may elicit little reaction, but can cause in inflammatory reaction with reddening and edema of the wall.

General Microscopic Description:

• The histologic findings are quite variable ranging from little to quite marked inflammatory reactions or hypersensitivity reactions.
• If perforation has occured the findings are those of acute peritonitis.

Clinical Correlations:

• The presence of few worms may be asymptomatic.
• The most common symptoms are vague abdominal pain or colicky pain.
• Large numbers of worms may present signs and symptoms of obstruction.
• Migration of adult worms may cause signs and symptoms of perforation, peritonitis, appendicitis or extrahepatic biliary obstruction.

References:
Sleisenger