|Three adult Hymenolepis nana|
Many, see text
Hymenolepididae is family of cyclophyllid tapeworms. The characteristic feature is the small number of testes (one to four). The unilateral genital pores and large external seminal vesicle allows for easy recognition. Most species are small, transparent, and easy to study.
As human parasites
The family Hymenolepididae has only two species which infects humans: the disease hymenolepiasis is caused by Hymenolepis nana and H. diminuta which are sometimes placed in Rodentolepis. Hymenolepiasis occurs not too rarely in school-aged children. H. nana also infects other mammals, like rodents. It is unique[verification needed] among tapeworms in that an intermediate host is optional. Pathological effects of infection are rare and occur in massive infections through auto-infection. With increasing worm burden, symptoms such as restlessness, irritability, diarrhea, and abdominal pain. Humans become infected when they ingest infective eggs, through direct fecal-oral exposure. Diagnosis can be made by discovery of eggs in stool.
H. diminuta is primarily a parasite of rats, but human infections occur as incidental hosts. It is a larger species than H. nana and lacks hooks on the rostellum; it has three testes per proglottid. It has been shown that more than 90 species of arthropods are suitable intermediate hosts, such as the grain beetles[verification needed]. Drugs commonly used for treatment of hymenolepiasis are praziquantel, niclosamide, and paromomycin.
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