HYMENOLEPIS NANA

1. 1
Amjad Khan Afridi
HYMENOLEPIS NANA
Hymenolepis nana is protozoan parasite which cause disease called Hymenolepiasis.
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.
History
In 1887, Grassi demonstrated that transmission from rat to rat did not require an intermediate
host. Later, in 1921, Saeki demonstrated a direct cycle of transmission of H. nana in humans,
transmission without an intermediate host. In addition to the direct cycle, Nicholl and Minchin
demonstrated that fleas can serve as intermediate hosts between humans.
Life cycle
 Direct life cycle: through ingestion of infectious eggs.
 Eggs may be passed directly from person to person, usually by children.
 Eggs may be ingested in food, especially grain products contaminated by rodent
droppings (parasite is common in mice).
 Indirect life cycle: through ingestion of intermediate hosts (usually grain beetles)
containing cysticercoid larvae; less common.
 After human ingestion, eggs hatch in intestine and embryos penetrate the mucosa, where
they mature as cysticercoid larvae.
 Larvae subsequently emerge and reattach to the intestinal wall to complete their
development into adult tapeworms in 2 - 3 weeks.
 Internal autoinfection: if eggs hatch shortly after being discharged from worm and rapidly
invade the intestinal wall without leaving the body.

2. 2
Amjad Khan Afridi
Symptoms
Symptoms occur only with heavy infections. Symptoms include:
 Diarrhea
 Gastrointestinal discomfort
 Itchy anus
 Poor appetite
 Abdominal pain
 Headaches and weakness
 Poor appetite
 Dehydration (due to long-term diarrhea)
Diagnosis
 Recovery of oval, thin shelled, colorless eggs, 30 - 47 μm, from stool
 Scolex has an armed rostellum
 Proglottids have all of their genital pores located on same side of strobila

3. 3
Amjad Khan Afridi
Treatment
Praziquantel, adults and children, 25mg/kg in a single-dose therapy.
Alternatives:
Niclosamide:adults, 2 gm in a single dose for 7 days; children 11-34 kg, 1 gm in a single dose on
day 1 then 500 mg per day orally for 6 days; children > 34 kg, 1.5 gm in a single dose on day 1
then 1 gm per day orally for 6 days.
Nitazoxanide:adults, 500 mg orally twice daily for 3 days; children aged 12-47 months, 100 mg
orally twice daily for 3 days; children 4-11 years, 200 mg orally twice daily for 3 days.
Oral praziquantel is available for human use in the United States.
Niclosamide is unavailable in the United States.
Nitazoxanide is available for human use in the United States.
Prevention
 Good hygiene
 Public health and sanitation programs
 Elimination of infected rats help to prevent the spread of hymenolepiasis.
 Preventing fecal contamination of food and water in institutions and crowded areas is of
primary importance.
 General sanitation and rodent and insect control (especially control of fleas and grain
insects) are also essential for prevention of H. nana infection.