Microbiology Case Study: Worm Seen in Toddler’s Stool

Case History

A worm specimen—as shown in Image 1—was found in a stool sample from a 21 month old, otherwise healthy female.

Image 1. Specimen collect from patient’s stool.

Discussion

The worm specimen in question is Ascaris lumbricoides, the largest of the nematode parasites. Females typically measure 20-35 cm long with straight tails, while males are smaller at 15-31 cm with curved tail.1 A characteristic feature in adults of both sexes are the three “lips” at the anterior end of the body, as shown in Image 2.

Image 2. Close up of the anterior end of an adult A. lumbricoides. Three “lips” are highlighted with a black arrow.

Humans are the definitive host for these roundworm parasites. Infection with these soil-transmitted helminths is quite common, with an estimated 807 million to 1.2 billion people affected.2,3 Children are infected much more frequently than adults.4 Nearly all A. lumbricoides cases occur in tropical and subtropical areas of Asia, sub-Saharan Africa, and the Americas. This infection is rare or absent in developed countries, but sporadic cases may occur in rural regions.3

Individuals affected with adult Ascariasis worms usually show no acute symptoms. However, since these worms are commonly situated in the small intestines, the clinical presentation of a heavy worm burden in children might include stunted growth via malnutrition. In both adults and children, a high worm burden may result in abdominal pain and intestinal obstruction leading to potential perforations. Migrating worms may lead to symptomatic occlusion of the biliary tract, appendicitis, or nasopharyngeal expulsion.3

In the clinical setting and for diagnosis, A. lumbricoides eggs should be found in the feces, juvenile worms in the sputum, and in some cases adults in the feces. For deworming, the recommended treatment are anti-helminthic medications such as albendazole and mebendazole.3 These medications kill the adults, but not the migrating larvae thus repeat treatment might be needed.

References

  1. Centers for Disease Control and Prevention. DPDx – Laboratory Identification of Parasites of Public Health Concern. Internet [updated July 19, 2019]. Available from: https://www.cdc.gov/dpdx/ascariasis/index.html.
  2. Jourdan PM, Lamberton PHL, Fenwick A, Addiss DG. Soil-transmitted helminth infections. Lancet. 2018;391(10117):252-65. Epub 2017/09/09. doi: 10.1016/s0140-6736(17)31930-x. PubMed PMID: 28882382.
  3. Centers for Disease Control and Prevention. Parasites – Ascariasis. Internet [updated November 23, 2020]. Available from: https://www.cdc.gov/parasites/ascariasis/index.html.
  4. Veesenmeyer AF. Important Nematodes in Children. Pediatr Clin North Am. 2022;69(1):129-39. Epub 2021/11/20. doi: 10.1016/j.pcl.2021.08.005. PubMed PMID: 34794670.

-Amelia Lamberty is a Masters Student in the Department of Pathology and Laboratory Medicine at the University of Vermont.

-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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