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An Ascaris lumbricoides-roundworm seen in the common bile duct in an ERCP-examination
Ascariasis A disease caused by Ascaris lumbricoides, a parasitic roundworm. This is the most common parasitic worm disease in the world, very prevalent in tropical regions but found also in our country. In the United States about 4 million people are infected. The adult worm is 30 cm long and 2-6 mm wide. The female worm produces 200.000 eggs per day. The eggs (ova) are leave the body in the stools and they can be viable on the soil for years. After infective eggs are swallowed, the larvae hatch, invade the intestinal wall, and are carried via the blood circulation to the lungs . The larvae mature further in the lungs, penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed, once again. In the small instestine they then develop into adult worms Upon reaching the small intestine, they develop into adult worms.
An Ascaris lumbricoides-roundworm coming out throught the Papilla Vater
The patient can be completely free of symptoms, but in the larvae stage the infection can cause peritonitis or pneumonia and in the worm stage it can cause dyspeptic symptoms and weight loss and bowel obstruction especially in children. Cholangitis and pancreatitis can be caused by worms in the bile or pancreatic ducts. Drug treatment is effective, the two most commonly used drugs are mebendazole and piperazine. Good hygiene is the most important prevention.
The life cycle of the Ascaris lumbricoides
Adult worms (1) live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the feces (2). Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks (3), depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed (4) the larvae hatch (5), invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs (6). The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed (7). Upon reaching the small intestine, they develop into adult worms (1). Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years.
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