The section through the lumen of the appendix reveals a female pinworm, Enterobius vermicularis. This is a common parasitic infection, seen most frequently in children. The adult female worm, which measures 8 to 13 mm long and 0.3 to 0.5 mm in diameter, resides in the lower gastrointestinal tract (colon or appendix). Lateral alae extend most of the length of the worm. In this cross section, numerous eggs measuring 50 to 60 microns by 20 to 30 microns are seen. The eggs are flattened on one side. The female migrates to the perianal region to lay eggs, resulting in pruritis ani. Direct ano-oral infection can occur; the eggs can remain viable in the environment for two weeks and are resistant to most household disinfectants.
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