Hymenolepis nana

Source

Rosanna Falbo, M.D., Department of Laboratory Medicine, Desio Hospital, University Milano Bicocca, Desio, Italy.

Description

An egg of the parasite Hymenolepis nana (arrow), which was found in the urine of a 8-month-old baby as the result of faecal contamination. Eggs are oval or spherical, with a size of 40-60 x 30-50 μm, and are characterized by one inner and one external membrane. The eggs of this parasite - which is found worldwide, most often in children who live in poor sanitary conditions - enter the body through contaminated food. Once in the intestine, the eggs release the oncospheres (= the larval forms of the parasite), which penetrate the intestinal villus and develop into cysticercoid larvae. Upon rupture of the villus, the cysticercoids return to the intestinal lumen, evaginate their scoleces (= the worm’s heads), which attach to the intestinal mucosa and develop into adults. These reside in the ileal portion of the small intestine producing gravid proglottides (= the segments of parasite containing reproductive organs), which release the eggs in the stool.

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