Ascariasis

• Glenn G. Fort, M.D., M.P.H.

 Basic Information

Definition

Ascariasis is a parasitic infection caused by the nematode Ascaris lumbricoides. The majority of those infected are asymptomatic; however, clinical disease may arise from pulmonary hypersensitivity, intestinal obstruction, and secondary complications.

Synonyms

1. Round worms

2. Worms

ICD-10CM CODES
B77.9	Ascariasis, unspecified
B77.81	Ascariasis pneumonia
B77.0	Ascariasis with intestinal complications
B77.89	Ascariasis with other complications

Epidemiology & Demographics

Incidence (In U.S.)

1. •

   Unknown. Worldwide, A. lumbricoides is the most common helminthic infection of humans, infecting as many as 1 billion or more persons. 71% of persons at risk for infection live in Asia and the Western Pacific.

2. •

   Three times the infection rates found in blacks as in whites

Peak Incidence

Unknown

Prevalence (In U.S.)

Estimated at 4 million, the majority of which live in the rural southeastern part of the country; ascariasis is associated with poor sanitation

Predominant Sex

Both sexes probably equally affected, with a possible slight female preponderance

Predominant Age

Most common in children from ages 2 to 10 years old and decreases after age 15; infections tend to cluster in families

Neonatal Infection

Probable transmission, though not specifically studied

Physical Findings & Clinical Presentation

1. •

   Most people infected with Ascaris are asymptomatic.

2. •

   Occurs approximately 9 to 12 days after ingestion of eggs (corresponding to the larval migration through the lungs)

3. •

   Nonproductive cough

4. •

   Substernal chest discomfort

5. •

   Fever

6. •

   In patients with large worm burdens, especially children, intestinal obstruction associated with perforation, volvulus, and intussusception

7. •

   Migration of worms into the biliary tree giving clinical appearance of biliary colic and pancreatitis as well as acute appendicitis with movement into that appendage

8. •

   Rarely, infection with A. lumbricoides producing interstitial nephritis and acute renal failure

9. •

   In endemic areas in Asia and Africa, malabsorption of dietary proteins and vitamins as a consequence of chronic worm intestinal carriage; 1 billion people worldwide are infected with this nematode

Etiology

1. •

   Transmission is usually hand to mouth, but eggs may be ingested via transported vegetables grown in contaminated soil.

2. •

   Eggs are hatched in the small intestine, with larvae penetrating intestinal mucosa and migrating via the circulation to the lungs.

3. •

   Larval forms proceed through the alveoli, ascend the bronchial tree, and return to the intestines after swallowing, where they mature into adult worms.

4. •

   Estimated time until the female adult worm begins producing eggs is 2 to 3 mo.

5. •

   Eggs are passed out of the intestines with feces and can survive for years in warm, moist, shaded soil.

6. •

   Within human host, adult worm life span is 1 to 2 yr.

Diagnosis

Differential Diagnosis

1. •

   Radiologic manifestations and eosinophilia to be distinguished from drug hypersensitivity and Löffler’s syndrome.

2. •

   Table E1 compares features of major intestinal nematodes.

Laboratory Tests

1. •

   Examination of the stool for Ascaris ova (Fig. E1)

   

2. •

   Expectoration or fecal passage of adult worm

3. •

   Adult male worms: 10 to 30 cm long; adult female worms: larger than male, up to 40 cm

4. •

   Eosinophilia: most prominent early in the infection and subsides as the adult worm infestation established in the intestines; usually in 5% to 12% range but can be up to 50%

5. •

   Serology: patients develop IgG antibodies, but they cross react with antigens from other helminths and are not protective; thus serology is used more for epidemiologic purposes than for individual diagnosis

Imaging Studies

1. •

   Chest x-ray to reveal bilateral oval or round infiltrates of varying size (Löffler’s syndrome); NOTE: infiltrates are transient and eventually resolve.

2. •

   Plain films of the abdomen and contrast studies to reveal worm masses in loops of bowel.

3. •

   Ultrasonography and endoscopic retrograde cholangiopancreatography (ERCP) to identify worms in the pancreaticobiliary tract.

4. •

   CT scan with oral contrast can also assist in the detection of GI foreign bodies such as parasites.

Treatment

Nonpharmacologic Therapy

Aggressive IV hydration, especially in children with fever, severe vomiting, and resultant dehydration

Acute General Rx

1. •

   All infected patients, including asymptomatic ones, should be treated.

   1. 1.

      Albendazole: 400 mg PO × 3 days is the first-line agent. Single-dose albendazole is used in mass treatment campaigns.

   2. 2.

      Mebendazole 100 mg PO bid y × 3 days

2. •

   Cure rate with these agents is 95% to 100%, but they are contraindicated in pregnancy.

3. •

   Side effects: GI discomfort, headache, and rarely leukopenia

4. •

   Alternative agent or for use in pregnancy: pyrantel pamoate (Antiminth)

   1. 1.

      Given at a dose of 11 mg/kg PO (maximum dose of 1 g/day)

   2. 2.

      Considered safe for use in pregnant women

5. •

   Other alternative agents:

   1. 1.

      Ivermectin: 150 to 200 mcg/kg orally once

   2. 2.

      Nitazoxanide: Ages 2 to 3 yrs: 100 mg/5 ml BID × 3 days, and ages 4 to 11 yrs: 200 mg/10 ml BID × 3 days. Cure rates in heavy worm burden are only 50% to 80%

   3. 3.

      Piperazine citrate: no longer first-line agent due to toxicity but still used in cases of intestinal or biliary obstruction, as drug paralyzes the worm, helping its expulsion. Dose: 50 to 75 mg/kg once daily up to maximum of 3.5 g for 2 days

   4. 4.

      Levamisole: 2.5 mg/kg once orally is recommended by the WHO as alternative therapy, but not available in the U.S.

6. •

   Complete obstruction should be managed surgically.

Disposition

Overall prognosis is good. Patients should be reevaluated in 2 to 3 months. Reinfection is common.

Referral

1. •

   To gastroenterologist in cases of visualized pancreaticobiliary tract or appendiceal obstruction

2. •

   To surgeon in cases of complete obstruction or suspected secondary complication (e.g., perforation or volvulus)

 

Pearls & Considerations

Comments

1. •

   Hepatic abscess, containing both viable and dead worms, complicating Ascaris-induced biliary duct disease has been documented.

2. •

   Given the known transmission of the parasite, routine hand washing with soap and proper disposal of human waste would significantly decrease the prevalence of this disease.

3. •

   Other protective measures to avoid ingestion of worm eggs:

   1. 1.

      Peel or cook food.

   2. 2.

      Boil drinking water.

   3. 3.

      Do not place small children directly on soil.

Suggested Readings

• A.K. Das: Hepatic and biliary ascariasis. J Glob Infect Dis. 6:65–72 2014 24926166

• C. Dold, C.V. Holland: Ascaris and ascariasis. Microbes Infect. 13:632–637 2011 20934531

• P.H. Lamberton, P.M. Jourdan: Human ascariasis: diagnostic update. Curr Trop Med Rep. 2:189–200 2015 26550552

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