Microbiology Case Study: Specimen Referral from a 20 Month Old Male

Case History

A 20 month old male presented to an outside hospital with symptoms unknown to our laboratory. That laboratory sent us the specimen recovered from a diaper (Image 1).

Image 1.


The nematode Ascaris lumbricoides is one of the most common helminth infections in the United States. It can grow to be 20-35 cm long. Infection occurs when an egg is ingested, usually in a small child eating dirt contaminated with human feces. When the larvae hatch they penetrate the duodenal wall. From there, the larvae go into the blood stream and eventually end up in the pulmonary circulation where the larvae grow in the alveoli.  In about three weeks, the larvae are coughed up from the lungs and swallowed.  The worms then mature in the jejunum (primarily).  Infection most often shows no symptomatology. If symptoms are present, they can range from mild abdominal discomfort to intestinal blockage and even cough as the worms migrate to the lungs [1].

Diagnosis can be made by examining concentrated stool for knobby-coated, bile-stained eggs that are oval [2].  However, some of the adult worms can pass with the feces.


  1. https://www.cdc.gov/parasites/ascariasis/index.html
  2. Murray PR, Rosenthal KS, Pfaller MA. Medical Microbiology, Seventh Edition. Elsevier Health Sciences; 2012.


-Angela Theiss, MD is a 1st year anatomic and clinical pathology resident at the University of Vermont Medical Center.


-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.

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