Ascaris Infection - Diagnosis 

The  diagnosis is usually incidental when the host passes a worm in the stool or vomit. Stool samples for ova and parasites will demonstrate Ascaris eggs. Larvae may be found in gastric or respiratory secretions in pulmonary disease. Blood counts may demonstrate peripheral eosinophilia. On X-ray, 15-35 cm long filling defects, sometimes with whirled appearance (bolus  of worms).

Diagnostic Findings 

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

• Collect  a stool specimen. 
• Fix the specimen in 10% formalin. 
• Concentrate using the formalin–ethyl acetate sedimentation technique. 
• 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. 

Ultrasound :

Macroscopic Findings 

• Fertilized eggs are rounded, have a thick shell, with an external mammillated layer that  is often stained brown by bile. In some cases, the outer layer is absent. Size: approximately 60 µm in diameter when spherical, and up to 75 µm when ovoid. 

• Unfertilized eggs are elongated and larger (up to 90 µm in length); their shell is thinner; and their mammillated layer is more variable, either with large protuberances or practically none; these eggs contain mainly a mass of refractile granules. 

• Fertilized Ascaris egg, still at the unicellular stage. Eggs are normally at  this stage when passed  in the stool. Complete development of the larva requires 18 days under favorable conditions. 

• Unfertilized and fertilized eggs 

• Unfertilized egg. Prominent mammillations of outer layer. 

• Fertilized egg. The embryo can be distinguished inside the egg. 

• Unfertilized egg with no outer mammillated layer (decorticated). 

• Three fertilized eggs (one decorticated, on the right) of Ascaris lumbricoides. 

• Two fertilized eggs from the same patient, where embryos have begun  to develop (this happens when the stool sample is not processed for several days without refrigeration). The embryos in early stage of division (4  to 6 cells) can be clearly seen. 

• Egg containing a larva, which will be infective if ingested. 

• Larva hatching from an egg.