Hymenolepis Nana The Dwarf Tapeworm Geographical Distribution Most

Hymenolepis Nana The Dwarf Tapeworm

Geographical Distribution ● Most common cestode infection around the world ● Affects mainly children Habitat ● Small intestine of man

Morphology ● Smallest tapeworm infecting man(2 -6 cm) ● Scolex has four suckers and rostellum with hooks. ● Segments

Morphology Eggs are spherical, transparent, 40 um in diam. They contain the hexacanth embryo surrounded by 2 shells. The inner shell has 2 knobs from which arise 4 -8 filaments.

Ingestion of egg Autoinfection Oncosphere hatches in ilieum Definitive host Cysticercoid in vili Adult in ilieum

Mode of infection in H. nana • Infective stage Eggs • Mode of infection: 1 - Ingestion of eggs • with contaminated soil, food or drinks 2 - Autoinfection • External autoinfection • Internal autoinfection • Hyperinfection in children or immunosuppressed patients

Life Cycle ● Hymenolepis nana is the only cestode infecting human that utilizes man as intermediate host and definitive host. ● Hyperinfection occurs when eggs do not pass in stools and hatch in the ileum penetrate the villi and develop into cycticercoids. This occurs if the patient is immunosuppressed.

How does man act as an intermediate host?

Clinical Picture ● May be asymptomatic ● May cause restlessness, irritability, headache, dizziness, anorexia, abdominal pain and diarrhoea. ● The mechanism by which symptoms are produced is usually allergic.

Diagnosis ● H. nana infections can be diagnosed accurately and rapidly by inspecting the stool for eggs.

Treatment ● Praziquantel is drug of choice for treatment of H. nana (kills adults and larvae since it is systemically absorbed) It is given in a single dose of 25 mg/Kg body weight. ● Niclosamide : should be given for 5 to 7 days since it affects adults in the lumen only.