Hymenolepididae is family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of cyclophyllid tapeworms. The characteristic feature is the small number of testes (one to four). The unilateral genital pores and large external seminal vesicle

Seminal vesicle

The seminal vesicles or vesicular glands are a pair of simple tubular glands posteroinferior to the urinary bladder of male mammals...

 allows for easy recognition. Most species are small, transparent, and easy to study.

As human pasasites

The family Hymenolepididae has only two species which infects humans: the disease hymenolepiasis

Hymenolepiasis

Hymenolepiasis is infestation by one of two species of tapeworm:* Hymenolepis nana* Hymenolepis diminutaAlternative names are:* Dwarf tapeworm infection* Rat tapeworm-Causes, incidence, and risk factors:...

 is caused by Hymenolepis nana

Hymenolepis nana

Dwarf tapeworm is a cosmopolitan species that is one of the most common cestodes of humans in the world, especially among children. It can be found throughout the world, but is usually most common in temperate zones...

and H. diminuta

Hymenolepis diminuta

Hymenolepis diminuta, also known as rat tapeworm, is a species of Hymenolepis tapeworm that causes hymenolepiasis. It has slightly bigger eggs and proglottids than H. nana and infects mammals using insects as intermediate hosts...

which are sometimes placed in Rodentolepis. Hymenolepiasis occurs not too rarely in school-aged children. H. nana also infects other mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s, like rodent

Rodent

Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

s. It is unique 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 rat

Rat

Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

s, but human infections occur as incidental hosts. It is a larger species than H. nana and lacks hooks on the rostellum

Rostellum

The rostellum is a projecting part of the column in Orchidaceae flowers, and separates the male stamen from the female gynoecium, commonly preventing self-fertilisation...

; it has three testes per proglottid. It has been shown that more than 90 species of arthropod

Arthropod

An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

s are suitable intermediate host

Intermediate host

A secondary host or intermediate host is a host that harbors the parasite only for a short transition period, during which some developmental stage is completed. For trypanosomes, the cause of sleeping sickness, humans are the primary host, while the tsetse fly is the secondary host...

s, such as the grain beetle

Grain beetle

Grain beetle may refer to:*Foreign grain beetle*Merchant grain beetle*Saw-toothed grain beetle...

s.
Drugs commonly used for treatment of hymenolepiasis are praziquantel

Praziquantel

Praziquantel is an anthelmintic effective against flatworms. Praziquantel is not licensed for use in humans in the UK; it is, however, available as a veterinary anthelmintic, and is available for use in humans on a named-patient basis....

, niclosamide

Niclosamide

Niclosamide is a teniacide in the anthelmintic family especially effective against cestodes that infect humans...

, and paromomycin.

There is some confusion regarding the host specificity. It was found that the human strain

Strain (biology)

In biology, a strain is a low-level taxonomic rank used in three related ways.-Microbiology and virology:A strain is a genetic variant or subtype of a micro-organism . For example, a "flu strain" is a certain biological form of the influenza or "flu" virus...

of H. nana is essentially non-infective to rodents.