Ascaris lumbricoides

• large roundworm
• worldwide distribution; Highest prevalence in tropical areas and areas with inadequate sanitation.
• Most common helminthic infection worldwide; this worm is thought to infect approximately 4 million Americans and an estimated 1.4 billion individuals worldwide.
• Occurs in rural areas of Southeastern USA.

Presentation

• Although infections may cause stunted growth, adult worms usually cause no acute symptoms.
• the most common presentation is the passage of a worm in the stool.
• Although most infected individuals are asymptomatic, some present with coughing, wheezing, hemoptysis, colicky abdominal pain, or bilious emesis.
• High worm burdens may cause abdominal pain and intestinal obstruction. Biliary or complete intestinal may occur.

Transmission

• transmitted in a fecal-oral manner, primarily from the ingestion of food contaminated with parasite eggs.

Life Cycle

• Ingestion of infective eggs from contaminated soil results in infection, which is often asymptomatic.
• after ingestion Ascaris larvae hatch and are released into the intestine, Adult worms live in the small intestine from where they migrate to the lungs. During the lung phase of larval migration, pulmonary symptoms can occur (cough, dyspnea, hemoptysis, eosinophilic pneumonitis - Loeffler’s syndrome).
• After 1-2 weeks, the partially developed larvae ascend the trachea and are reswallowed.
• They then develop into mature worms and produce eggs that are excreted in the stool.
• The worms can reach up to 30 cm in length.
• Migrating adult worms may cause symptomatic occlusion of thebiliarytract or oral expulsion.

Treatment

• Ova and parasites may be found in the stool. Adult worms are occasionally passed in the stool or through the mouth or nose.
• oral mebendazole 100 mg administered twice a day for 2 days or
• oral albendazole 400 mg given once, with another dose given at 3 weeks.
• Flaccid paralyzing agents, such as piperazine citrate, are preferred when intestinal obstruction is suspected.
• Pyrantel pamoate, a spastic paralyzing agent, is easier to administer as a single dose, but it increases the risk of intestinal obstruction.

Follow-up: Re-examine stool 3 weeks after therapy confirm treatment success.

For more information about ascariasis, see the eMedicine articles Ascariasis (within the Pediatrics specialty) and Ascariasis and Nematode Infections (within the Internal Medicine  specialty).
CHLA Board Review 2005