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Hymenolepis nana

Common name. Dwarf tapeworm

Disease. hymenolepiasis

Geographic distribution. Worldwide, but more frequent in hot countries. Portugal, Spain, Sicily, Egypt, Sudan, India, etc.

Infection rate. The incidence of infection in man ranges from less than 1 to 28%.

Life cycle. H.nana can develop directly in the small intestine of the definitive hosts as well as in an intermediate hosts (insects). If larva-bearing eggs enter the human gastrointestinal tract, the oncospheres are released into the duodenum and attatch to the villi, where each develops into a cysticercoid. Within 2-3 weeks, the cysticercoid develops into a tapeworm. It is a common parasite of the house mice and is found in human, especially in children.

Morphology. Adult worm is only 10-45 mm long and 0.5-1 mm wide, with 100-200 segments. The eggs (30-50 ㎛) are oval to spherical and almost colorless.

Pathology and clinical symptoms. Light infections are asymtomatic. When large numbers of worms are present, they may give rise to abdominal pain, diarrhea, headache, anorexia and various non-specific symptoms.

Diagnosis. Detection of eggs in feces.

Prevention. Personal cleanliness, destruction of rats and mice, and a well-balanced diet to promote resistance to infection..

Hae-Jin Jeong

Egg of Hymenolepis nana from human.

Woon-Mok Sohn

Scolex of Hymenolepis nana.

Tai Soon Yong

Hymenolepis nana : Anterior part of scolex, Acetocarmine stain, X 450

Yong Suk Ryang

Hymenolepis nana : midle part of gravid proglottids, Acetocarmine stain, X200

Yong Suk Ryang

Hymenolepis nana : Midle part of gravid proglottids, Acetocarmine stain, X450

Yong Suk Ryang

The scolex of Hymenolepis nana shows suckers and an invaginated rostellum. x100.

Sung-Jong Hong

Scolex of Hymenolepis nana showing 2 suckers and rostellum with hooks(A). Mature proglottids have 3 testes (B) (Carmine stain).

DY Min/MH Ahn/JS Ryu