Ascaris Lumbricoides The 5 Minute Pediatric Consult


	Ascaris Lumbricoides

Janet H. Friday

Database
Differential Diagnosis
Data Gathering
Laboratory Aids
Therapy
Follow-Up

DATABASE

DEFINITION

Ascaris lumbricoides is a large roundworm, 15 to 40 cm in length, which infects humans via eggs found in soil. Animals are not affected. Approximately one-fourth of the world’s population is infested with this worm.

PATHOPHYSIOLOGY

The lifecycle begins when eggs are ingested from soil contaminated with human feces.
Subsequently, the larvae are liberated in the small intestine.
The rhabdoid larvae invade the venous system and travel to the portal circulation, inferior vena cava, and finally, pulmonary capillaries.
They penetrate the alveoli, and are subsequently expelled by coughing across the epiglottis and swallowed. During the migration of the parasite through the pulmonary vessels, an eosinophilic response is evoked.
The larvae become adult worms in the small intestine.
The cycle takes 2 months.
In the intestinal stage, mechanical obstruction from the mass of worms in the gut may be observed in children.

EPIDEMIOLOGY

One female worm produces 200,000 eggs per day.
Fertilized eggs must incubate in the soil for 2 to 3 weeks.
The eggs are viable for up to 6 years in temperate climates; they survive freezing but not direct sunlight.
All ages may be affected; however, children are more frequent hosts due to oral behavior.
Ascariasis is more common where sanitation is poor and population dense.

COMPLICATIONS

Bronchopneumonia may be seen during the migrational stage, producing fever, cough, dyspnea, wheeze, eosinophilia, and pulmonary infiltrates.
Heavy infestations may cause abdominal pain, malabsorption, and growth failure.
Children may experience obstruction (ileocecal), malabsorption, or intussusception.
Perforation of a viscus, or migration into the appendix, biliary, or pancreatic ducts may rarely occur.

PROGNOSIS

Once intestinal infection is detected and treated, the prognosis is excellent. If obstructive or respiratory complications have occurred, the prognosis is less favorable.
The case fatality rate in the United States is 3%.

DIFFERENTIAL DIAGNOSIS

Ascariasis should be considered in the differential diagnosis when a patient presents with pneumonia and peripheral eosinophilia.
The diagnosis of Ascaris infection should be considered whenever intestinal obstruction is seen in an endemic area.
This infection may be associated with other parasites acquired from contaminated soil.

DATA GATHERING

HISTORY

Question: Do patients infected with ascaris always have symptoms?
Significance: The majority of patients with moderate infections are asymptomatic.

Question: Do patients actually see worms in their stool?
Significance: History or passage of large worms in the stool or vomitus is suggestive.

Question: What are pulmonary symptoms?
Significance: During the pulmonary stage, cough, dyspnea, fever, and pulmonary infiltrates in the presence of eosinophilia suggest the diagnosis.

Question: Are there symptoms of obstruction?
Significance: Rarely, the infection presents as intestinal obstruction, with an incidence of approximately 2 children per 1000 infected.

LABORATORY AIDS

Test: Microscopic examination of stool specimens
Significance:

Will demonstrate the characteristic eggs.
During the pulmonary phase, eosinophils and larvae may be seen.
No serological tests are necessary, and are poorly specific to the diagnosis.

THERAPY

A single dose of pyrantel pamoate (11 mg/kg; maximum, 1 g) is effective.
Mebendazole (100 mg twice daily for 3 days) is effective, but not recommended for children under age 2.
Piperazine citrate (75 mg/kg/d for 2 days; maximum, 3.5 g) is suggested in cases of obstruction due to large worm bezoars to aid passage. It should not be administered with pyrantel pamoate.

PREVENTION

Infection Control

With appropriate disposal of human excrement and handwashing, this infection could be eliminated.
In communities with high Ascaris carriage, biannual administration of pyrantel pamoate or mebendazole is effective.

FOLLOW-UP

Treatment as specified above is highly effective. Reinfection is problematic in endemic areas.

ICD-9-CM 127.0

Reference

Katz M. Nemahelminthes. In: Feigin RD, Cherry JD, eds. Textbook of pediatric infectious diseases. Philadelphia: WB Saunders, 1987:2087–2099.

Oski FA, ed. Principles and practice of pediatrics. Philadelphia: JB Lippincott, 1990:1288–1289.

Peter G, ed. 1997 red book: report of the committee on infectious disease, American Academy of Pediatrics. Elk Grove Village, IL: American Academy of Pediatrics, 1997:142–143.

Plorde J. Intestinal nematodes. In: Braunwald E, et al., eds. Harrison’s principles of internal medicine. New York: McGraw-Hill, 1987:817–818.

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