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Hymenolepis nana (Dwarf Tapeworm) Infection
Hymenolepis nana, a tiny intestinal tapeworm, is the most common human cestode; infection is treated with praziquantel.
H. nana is only 15 to 40 mm long. It requires only one host but can also cycle through two. Its larvae migrate only within the gut wall, and its life span is relatively short (4 to 6 wk). H. nana is more frequent in populations living in conditions of poverty and poor hygiene, particularly when fleas are present.
H. nana has 3 modes of infection:
Indirect 2-host cycle: Rodents are the primary definitive hosts, and grain beetles, fleas, or other insects feed on contaminated rodent droppings as intermediate hosts; humans can become infected by ingesting parasitized insects.
Human-to-human oral-anal cycle: Eggs are passed from one human to another or recycle externally in a single host.
Internal autoinfection: Eggs hatch within the gut and initiate a 2nd generation without ever exiting the host. Autoinfection can result in massive numbers of worms, which can cause nausea, vomiting, diarrhea, abdominal pain, weight loss, and nonspecific systemic symptoms.
Infections are often asymptomatic, but heavy infections may cause crampy abdominal pain, diarrhea, anorexia, weight loss and pruritis ani.
Diagnosis is made by finding eggs in stool samples.
Praziquantel 25 mg/kg po once is the treatment of choice.
Alternatives include nitazoxanide and niclosamide (not available in the US).
For nitazoxanide, dosage is 500 mg po bid for 3 days for patients > 11 yr, 200 mg po bid for 3 days for children aged 4 to 11 yr, and 100 mg po bid for 3 days for children aged 1 to 3 yr.
For niclosamide, adult dosage is 2 g po once/day for 7 days. For children 11 to 34 kg, dosage is 1 g in a single dose on day 1, then 500 mg once/day for 6 days; for children > 34 kg, dosage is 1.5 g in a single dose on day 1, then 1 g once/day for 6 days.
Drug NameSelect Brand Names
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