Hymenolepiasis nana

Learning outcomes By the end of the lecture, you should be able to: Mention systematic position of Hymenolepis nana Mention geographic distribution of Hymenolepis nana. Enumerate Intermediate, and Definitive hosts of Hymenolepis nana. Explain life cycle of Hymenolepis nana. Mention habitat of Hymenolepis nana. Mention mode of infection by Hymenolepis nana. Mention pathology and clinical features of Hymenolepis nana. Diagnose Hymenolepis nana infection. Prevention & control of Hymenolepis nana.

http://www.dpd.cdc.gov/dpdx/HTML/ hymenolepiasis.htm Suggested Reading http://www.dpd.cdc.gov/dpdx/HTML/ hymenolepiasis.htm

Causal Agents Hymenolepiasis is a parasitic disease caused by dwarf tapeworms Hymenolepis nana. 

Systematic position Phylum: Platyhelminthes Class: Cestoda e.g. Hymenolepis nana. 

Hymenolepis (H.) nana (dwarf tapeworm) (More common in children)

Geographical distribution : Cosmopolitan Morphology of Adult & egg Adult is 1-3 cm (dwarf)- flat formed from scolex, immature segments, mature segments & gravid segments. Egg is ovoid, translucent, with two envelopes, contains hexacanth embryo

life cycle 1- The adult lives in the small intestine of human & rodents (definitive host) 2- Mature eggs pass with feces and are immediately infective (the infective stage & diagnostic stage in the same time) 3- When another human or the same man (autoinfection: feco-oral) ingest the eggs with food or drink (mode of infection), the oncosphere hatch in the small intestine , penetrates into the submucosa and grows into cysticercoid (the larval stage), and then returns to the intestinal lumen to be an adult worm (so human act as an intermediate & definitive host ) 4- Eggs appear in stool two weeks after infection and ingested by another human and so on.................

Life cycle of H. nana

Important points Definitive host: Man Intermediate host: Man Infective stage: egg Diagnostic stage: ...egg in stool. Mode of infection: Autoinfection and ingestion of eggs with contaminated food and drink

Pathogenicity & clinical picture 1- In light infections, usually there are no manifestations. 2-In heavy infections, mucosal ulcerations lead to enteritis manifested clinically by: abdominal discomfort, colic, diarrhea, passage of mucous

Diagnosis of hymneolepiasis nana infection 1- Stool examination for finding the characteristic eggs

Prevention & control 1- Personal cleanliness 2- Treatment of infected persons (treatment should be prolonged & repeated and include all contact family members to avoid autoinfection and inter-family transmission of infection ) 3-Infected persons must not work as a food handlers 4- Rodent control

1- Dwarf tapeworm is said to Hymenolepis nana 2-Cysticercoide is the infective stage of: 3- Man is DH and IH in

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