Hymenolepis

Hymenolepis is a genus of tapeworms (cestodes) in the family Hymenolepididae that parasitize the small intestine of vertebrates. The two species most relevant to human health are Hymenolepis nana, the dwarf tapeworm, and Hymenolepis diminuta, the rat tapeworm. The genus is characterized by parasitic life cycles that involve the small intestine of definitive hosts and, in some cases, intermediate hosts such as insects.

In H. nana, transmission is primarily fecal–oral and can occur directly from person to person. Eggs released in the stool are immediately infective and can hatch in the intestine, allowing autoinfection, which can lead to light or heavy worm burdens in individuals, especially children. H. diminuta requires an intermediate host, typically an arthropod such as a grain beetle; humans become infected by ingesting an infected arthropod or food contaminated with one.

Clinical presentation is usually mild or asymptomatic, but heavier infections can cause abdominal discomfort, anorexia, nausea, or diarrhea. Eosinophilia may be present in some cases. Diagnosis relies on identifying eggs or gravid proglottids in stool samples.

Treatment is effective with antiparasitic medications such as praziquantel or niclosamide. Prevention focuses on good sanitation, hand hygiene, proper food handling, thorough washing of fruits and vegetables, and minimizing ingestion of insects or contaminated grains. Household contacts may be evaluated and treated if infection is detected.