Parasites and Health [Last Modified: ]
[Ascaris lumbricoides]
Causal Agent Life Cycle Geographic Distribution Clinical Features Laboratory Diagnosis Treatment

Clinical Features:
Although infections may cause stunted growth, adult worms usually cause no acute symptoms.  High worm burdens may cause abdominal pain and intestinal obstruction.  Migrating adult worms may cause symptomatic occlusion of the biliary tract or oral expulsion.  During the lung phase of larval migration, pulmonary symptoms can occur (cough, dyspnea, hemoptysis, eosinophilic pneumonitis - Loeffler’s syndrome).

Laboratory Diagnosis:
Microscopic identification of eggs in the stool is the most common method for diagnosing intestinal ascariasis.  The recommended procedure is as follows:

  1. Collect a stool specimen.
  2. Fix the specimen in 10% formalin.
  3. Concentrate using the formalin–ethyl acetate sedimentation technique.
  4. Examine a wet mount of the sediment.

Where concentration procedures are not available, a direct wet mount examination of the specimen is adequate for detecting moderate to heavy infections.  For quantitative assessments of infection, various methods such as the Kato-Katz can be used.  Larvae can be identified in sputum or gastric aspirate during the pulmonary migration phase (examine formalin-fixed organisms for morphology).  Adult worms are occasionally passed in the stool or through the mouth or nose and are recognizable by their macroscopic characteristics.

Diagnostic findings

The drugs of choice for treatment of ascariasis are albendazole* with mebendazole, ivermectin*, and nitazoxanide as alternatives.  In the United States, ascariasis is generally treated for 1-3 days with medication prescribed by a health care provider.  The drugs are effective and appear to have few side effects.  For additional information, see the recommendations in The Medical Letter (Drugs for Parasitic Infections).

* This drug is approved by the FDA, but considered investigational for this purpose.


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