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Ascariasis
An estimated 807 to 1221 million people in the world are infected with Ascaris lumbricoides, the largest helminth to infect humans. The adult male measures 15 to 25 cm and is smaller than the female, which may be as large as 35 cm. These helminths may live for 10 to 18 months and usually copulate in the lumen of the small intestine; the mature female may produce up to 200,000 eggs daily.
The infection occurs when eggs are ingested from contaminated food or water. The eggs pass into the duodenum, where they liberate a larva that penetrates the small intestine and may reach the lungs ( Fig. 119.1 ; see also Fig. 123.1 ).
Ascariasis: Life Cycle of Ascaris lumbricoides.
A patient may have hypersensitivity reaction in the lung, causing the clinical manifestation of Löffler syndrome, which is usually self-limiting. Löffler syndrome manifests as an eosinophilic accumulation in the lung as a response to a parasitic infection. The larvae pass into the bronchi and are swallowed. They mature in the small intestine, where they copulate, and their eggs are passed into feces to complete the life cycle.
Clinical Picture
Once the worms reach the lower intestine, the symptoms of ascariasis develop depending on the worm load and the location of the parasite. Most of the patients with ascaris infection are asymptomatic or have mild abdominal discomfort, nausea, dyspepsia, or loss of appetite. A heavy worm load may cause weight loss or malnutrition. Complications of chronic ascariasis include intestinal obstruction, obstruction of bile and pancreatic ducts, appendicitis, intestinal perforation, intussusception, and bowel necrosis requiring emergent surgical intervention. The worms can also migrate to the pancreatic and biliary systems, resulting in duct obstruction with jaundice, cholecystitis, cholangitis, and/or pancreatitis, referred to as hepatobiliary ascariasis. Intestinal obstruction is common in children. Live worms have been noted in sputum and vomitus.
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