Sunday, July 24, 2011

Answer to Case 169

Answer: Hymenolepis nana tapeworm

Shown here are classic proglottids and eggs (in utero) of Hymenolepis spp. The small size and probable presence of polar filaments is consistent with Hymenolepis nana (see images below).

As nicely stated by L.R., "adults only get to around 30-45 mm. The worm has an interesting life cycle flexibility - it can be transmitted via a direct transmission route from person to person as well as being transmitted by fleas which can serve as intermediate hosts/vectors."

As MicrobeMan correctly mentions, the eggs are somewhat distorted due to tissue fixation, processing and sectioning, and thus do not appear as spherical as would be expected in a stool preparation. They are also in utero, and some may be immature. An image of how the eggs typically look in stool can be seen at a previous post HERE.

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