Most infections with Ascaris lumbricoides are asymptomatic, although moderate to heavy infections may lead to malnutrition and nonspecific gastrointestinal tract symptoms. During the larval migratory phase, an acute transient pneumonitis (Löffler syndrome) associated with fever and marked eosinophilia may occur. Acute intestinal obstruction has been associated with heavy infections. Children are prone to this complication because of the small diameter of the intestinal lumen and their propensity to acquire large worm burdens. Worm migration can cause peritonitis, secondary to intestinal wall perforation, and common bile duct obstruction resulting in biliary colic, cholangitis, or pancreatitis. Adult worms can be stimulated to migrate by stressful conditions (eg, fever, illness, or anesthesia) and by some anthelmintic drugs. A lumbricoides has been found in the appendiceal lumen in patients with acute appendicitis.

Etiology

A lumbricoides is the most prevalent of all human intestinal nematodes (roundworms), with more than 1 billion people infected worldwide.

Epidemiology

Adult worms live in the lumen of the small intestine. Female worms produce approximately 200 000 eggs per day, which are excreted in stool and must incubate in soil for 2 to 3 weeks for an embryo to become infectious. Following ingestion of embryonated eggs, usually from contaminated soil, larvae hatch in the small intestine, penetrate the mucosa, and are transported passively by portal blood to the liver and lungs. After migrating into the airways, larvae ascend through the tracheobronchial tree to the pharynx, are swallowed, and mature into adults in the small intestine. Infection with A lumbricoides is widespread but is most common in the tropics, in areas of poor sanitation, and where human feces are used as fertilizer. If infection is untreated, adult worms can live for 12 to 18 months, resulting in daily fecal excretion of large numbers of ova. Female worms are longer than male worms and can measure 40 cm in length and 6 mm in diameter.

The incubation period (interval between ingestion of eggs and development of egg-laying adults) is approximately 8 weeks.

Diagnostic Tests

Ova can be detected by microscopic examination of stool. Occasionally, patients pass adult worms from the rectum, from the nose after migration through the nares, and from the mouth, usually in vomitus. Adult worms sometimes are detected by computed tomographic scan of the abdomen or by ultrasonographic examination of the biliary tree.

Treatment

Albendazole taken with food in a single dose, mebendazole for 3 days, or ivermectin taken on an empty stomach in a single dose are recommended for Treatment of ascariasis (see Drugs for Parasitic Infections). Although limited data suggest that these drugs are safe in children younger than 2 years of age, the risks and benefits of therapy should be considered before administration. In 1-year-old children, the World Health Organization recommends reducing the albendazole dose to half of that given to older children and adults. Albendazole is not labeled for use for Treatment of ascariasis. Nitazoxanide also is effective against A lumbricoides , although it also is not approved for this indication. Reexamination of stool specimens 2 weeks after therapy to determine whether the worms have been eliminated is helpful for assessing therapy but is not essential.

Conservative management of small bowel obstruction, including nasogastric suction and intravenous fluids, may result in resolution of major symptoms before administration of anthelminthic therapy. Piperazine, which may relieve intestinal obstruction caused by heavy worm burden, is not available in the United States. Surgical intervention occasionally is necessary to relieve intestinal or biliary tract obstruction or for volvulus or peritonitis secondary to perforation. Endoscopic retrograde cholangiopancreatography has been used successfully for extraction of worms from the biliary tree.

Isolation of the Hospitalized Patient

Standard precautions are recommended, because there is no direct person-to-person transmission.

Control Measures

Sanitary disposal of human feces stops transmission. Children's play areas should be given special attention. Vegetables cultivated in areas where uncomposted human feces are used as fertilizer must be thoroughly cooked or soaked in a diluted iodine solution before eating. Despite relatively rapid reinfection, frequent deworming of school-aged children may prevent morbidity (nutritional and cognitive deficits) associated with soil-transmitted nematode infections.