[Hymenolepis diminuta] [Hymenolepis nana]
Hymenolepiasis is caused by two cestodes (tapeworm) species, Hymenolepis nana (the dwarf tapeworm, adults measuring 15 to 40 mm in length) and Hymenolepis diminuta (rat tapeworm, adults measuring 20 to 60 cm in length). Hymenolepis diminuta is a cestode of rodents infrequently seen in humans and frequently found in rodents.
Hymenolepis nana is the most common cause of all cestode infections, and is encountered worldwide. In temperate areas its incidence is higher in children and institutionalized groups. Hymenolepis diminuta, while less frequent, has been reported from various areas of the world.
Hymenolepis nana and H. diminuta infections are most often asymptomatic. Heavy infections with H. nana can cause weakness, headaches, anorexia, abdominal pain, and diarrhea.
Hymenolepis diminuta eggs in wet mounts.
Hymenolepis nana egg in wet mounts.
Hymenolepis nana eggs, zinc PVA trichrome stain.
Intermediate hosts of Hymenolepis spp.
The diagnosis depends on the demonstration of eggs in stool specimens. Concentration techniques and repeated examinations will increase the likelihood of detecting light infections.
DPDx is an educational resource designed for health professionals and laboratory scientists. For an overview including prevention, control, and treatment visit www.cdc.gov/parasites/.