__NOTOC__ The Hymenolepididae are

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

cyclophyllid Tapeworms of the order Cyclophyllidea (the cyclophyllid cestodes) are the most important cestode parasites of humans and domesticated animals. All have multiple proglottid "segments", and all have four suckers on their scolices (heads), though ...

tapeworm Eucestoda, commonly referred to as tapeworms, is the larger of the two subclasses of flatworms in the class Cestoda (the other subclass is Cestodaria). Larvae have six posterior hooks on the scolex (head), in contrast to the ten-hooked Cestodar ...

s. Their characteristic feature is the small number of

testes A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testoster ...

(one to four). The unilateral

genital pore A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, a ...

s and large external

seminal vesicle The seminal vesicles (also called vesicular glands, or seminal glands) are a pair of two convoluted tubular glands that lie behind the urinary bladder of some male mammals. They secrete fluid that partly composes the semen. The vesicles are 5� ...

allow for easy recognition. Most species are small, transparent, and easy to study. The family contains over 90 genera with over 900 species, having as their

definitive host In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

birds (c. 700 species) or mammals (about 250 species). Most reside in the intestines of their definitive hosts. The majority of species with known lifecycles have

arthropods Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

intermediate hosts In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

As human parasites

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

hymenolepiasis Hymenolepiasis is infestation by one of two species of tapeworm: ''Hymenolepis nana'' or '' H. diminuta''. Alternative names are dwarf tapeworm infection and rat tapeworm infection. The disease is a type of helminthiasis which is classified as a n ...

is caused by ''

Hymenolepis nana Dwarf tapeworm (''Hymenolepis nana'', also known as ''Rodentolepis nana'', ''Vampirolepis nana'', ''Hymenolepis fraterna'', and ''Taenia nana'') is a cosmopolitan species though most common in temperate zones, and is one of the most common ces ...

'' and '' H. diminuta'', which are sometimes classified in the genus ''Rodentolepis''. Most cases of hymenolepiasis are caused by ''H. nana''. It occurs worldwide, but in temperate climates, children and people living in institutions are more likely to be infected. A morphologically-identical variety of ''H. nana'', ''H. nana'' var. ''fraterna'' infects

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

s, but the human

strain Strain may refer to: Science and technology * Strain (biology), variants of plants, viruses or bacteria; or an inbred animal used for experimental purposes * Strain (chemistry), a chemical stress of a molecule * Strain (injury), an injury to a mu ...

of ''H. nana'' is essentially non-infective to rodents. Unlike most tapeworms, including ''H. diminuta'', ''H. nana'' can complete its lifecycle without an intermediate host. Pathological effects of infection are rare and occur in massive infections through autoinfection, where the parasite is able to complete its lifecycle within the intestine of the human host, without passing through an intermediate host outside the body. With increasing worm burden, symptoms such as restlessness, irritability, diarrhea, and abdominal pain occur. ''H. diminuta'' is primarily a parasite of

rat Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include ''Neotoma'' ( pack rats), ''Bandicota'' (bandicoot ...

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

rostellum The rostellum is a projecting part of the column in Orchidaceae flowers, and separates the male androecium from the female gynoecium, commonly preventing self-fertilisation. In many orchids, such as ''Orchis mascula'', the pollinia or pollen masse ...

; it has three testes per

proglottid Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, known as tapeworms. Their bodies consist of man ...

. Species from a diverse set of

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

taxa, including earwigs, butterflies, and beetles, can be

intermediate host In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

s for this species, which is unusual for a tapeworm. Grain beetles are common intermediate hosts, because they live in piles of grain where they can be ingested by rats, which are the definitive hosts. Drugs commonly used for treatment of hymenolepiasis are

praziquantel Praziquantel (PZQ), sold under the brandname Biltricide among others, is a medication used to treat a number of types of helminthiasis, parasitic worm infections in mammals, birds, amphibians, reptiles, and fish. In humans specifically, it is us ...

niclosamide Niclosamide, sold under the brand name Niclocide among others, is an anthelmintic medication used to treat tapeworm infestations, including diphyllobothriasis, hymenolepiasis, and taeniasis. It is not effective against other worms such as flukes ...

, and

paromomycin Paromomycin is an antimicrobial used to treat a number of parasitic infections including amebiasis, giardiasis, leishmaniasis, and tapeworm infection. It is a first-line treatment for amebiasis or giardiasis during pregnancy. Otherwise it is g ...

Selected genera

* '' Allohymenolepis'' * '' Amphipetrovia'' * '' Aploparaxis'' * '' Armadolepis'' * '' Brachylepis'' * '' Branchiopodataenia'' * '' Cladogynia'' * '' Cloacotaenia'' * '' Colibrilepis'' * '' Confluaria'' * '' Coronacanthus'' * '' Dicranotaenia'' * '' Dildotaenia'' * '' Diorchis'' * '' Diploposthe'' * '' Dollfusilepis'' * '' Drepanidotaenia'' * '' Echinolepis'' * '' Fimbriaria'' * '' Flamingolepis'' * '' Hilmylepis'' * '' Hsuolepis'' * '' Hymenolepis'' (sometimes included in ''Rodentolepis'') * '' Mathevolepis'' * '' Passerilepis'' * '' Potorolepis'' * '' Pseudhymenolepis'' * '' Retinometra'' * '' Rodentolepis'' * '' Soricinia'' * '' Staphylocystis'' * '' Triodontolepis'' * '' Vampirolepis'' * '' Variolepis'' * '' Wardium''

References

Cestoda Platyhelminthes families {{Cestoda-stub