The dwarf tapeworm or Hymenolepis nana is found worldwide. Infection is most common in children, in persons living in institutional settings, and in people who live in areas where sanitation and personal hygiene is inadequate.
The life cycles consist of adult (tapeworm) stages in the small bowel of humans and rodents, and also larval tissue stages in insects (cysticercoid). In addition, the cysticer¬coid stages of H. nana can also invade and develop in the human intestine thus is capable of completing its entire life cycle in the human host. H nana can also be transmitted through autoinfection without having to pass through the insect host.
Most people who are infected do not have any symptoms. Those who have symptoms may experience nausea, weakness, loss of appetite, diarrhea, and abdominal pain. Young children, especially those with a heavy infection, may develop a headache, itchy bottom, or have difficulty sleeping. Sometimes infection is misdiagnosed as a pinworm infection.
Infection is most common in children aged 4-10 years, in dry, warm regions of the developing world. H nana infection affects millions of people, primarily children, worldwide. Estimated rates of infection in various regions range from 0.1-58%. It is estimated to have 50-75 million carriers of H. nana with 5 to 25% prevalence in children worldwide, which can be as high as 50% in children between 1-4 years of age. Regions with high reported infection rates include Sicily (46%), Argentina (34% of school children), and southern areas of the former Soviet Union (26%). In contrast, only 0.1% of stools examined at a children's hospital in Calgary were positive for H nana. Most cases with associated neurologic symptoms have been reported from the former Soviet Union.
• Alternatively, nitazoxanide or, outside the US, niclosamide 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.