Moniezia expansa
Encyclopedia
Moniezia expansa is commonly known as sheep tapeworm or double-pored ruminant tapeworm. It is a large tapeworm inhabiting the small intestine
s of ruminants such as sheep, goat
s and cattle
. It has been reported from Peru
that pigs
are also infected. There is an unusual report of human infection in an Egyptian.
It is characterized by unarmed scolex (i.e., hooks and rostellum
are absent), presence of two sets of reproductive system
s in each proglottid, and each proglottid being very short but very broad.
. It is an extremely long tapeworm, and can reach an enormous length up to 6–10 m. The scolex bears four large suckers, which are the holdfast organs to the host. There are no rostellum and rostellar hooks, and the suckers are devoid of spines. The boundary between the proglottids are studded with a row of interproglottid glands, which are yet undefined in terms of function.
The tapeworm, being monecious, contains both male and female reproductive organs in an individual. Thus each proglottid is a complete reproductive unit. Moreover, one defining feature of the genus is that there are two sets of reproductive organs situated at lateral sides with the associated cirrus pouches and genital pores in each proglottid. The testes are numerous.
as intermediate host
s. Eggs are passed out from the intestine
of the ruminant host along the gravid proglottids in the feces
into the soil. The eggs are eaten by soil mites
. Eggs must reach the gut of mite hosts within 1 day of release otherwise they are desiccated
. However, chances of development is very good as soil mites can be so numerous on a pasture
that even if only 3% are infected (with 4-13 cysticercoid
s each), a grazing ruminant may ingest over 2,000 cysticercoids per kilogram
of grass. Once inside the intestine of mites, the eggs hatch and the oncospheres penetrate into the haemocoel and develops to the cysticercoid stage. This stage may take up to 4 months. When the infected mite is eaten by the grazing ruminants, mature cysticercoids are digested out of the mite, and develop into mature tapeworms in the small intestine
within 5–6 weeks.
, even when the tapeworms are present in large numbers in young lambs
. However heavy infection may cause intestinal obstruction, diarrhea
and weight loss.
is done by analysis stool sample in which eggs can be detected, or often observation of the gravid proglottids in feces and anus
.
Niclosamide
is most often used. Praziquantel
is also 99–100% effective while albendazole
is 19-75% effective; and praziquantel + levamisole
combination is very effective in reducing worm burden and improvement of weight.
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
s of ruminants such as sheep, goat
Goat
The domestic goat is a subspecies of goat domesticated from the wild goat of southwest Asia and Eastern Europe. The goat is a member of the Bovidae family and is closely related to the sheep as both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...
s and cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
. It has been reported from Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
that pigs
PIGS
PIGS is a four letter acronym that can stand for:* PIGS , Phosphatidylinositol glycan anchor biosynthesis, class S, a human gene* PIGS , the economies of Portugal, Italy , Greece and Spain...
are also infected. There is an unusual report of human infection in an Egyptian.
It is characterized by unarmed scolex (i.e., hooks and 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...
are absent), presence of two sets of reproductive system
Reproductive system
The reproductive system or genital system is a system of organs within an organism which work together for the purpose of reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes...
s in each proglottid, and each proglottid being very short but very broad.
Structure
M. expansa has a typical cestode body, consisting of the anterior scolex, followed by the neck and a highly extended body proper, the strobilusStrobilus
A strobilus is a structure present on many land plant species consisting of sporangia-bearing structures densely aggregated along a stem. Strobili are often called cones, but many botanists restrict the use of the term cone to the woody seed strobili of conifers...
. It is an extremely long tapeworm, and can reach an enormous length up to 6–10 m. The scolex bears four large suckers, which are the holdfast organs to the host. There are no rostellum and rostellar hooks, and the suckers are devoid of spines. The boundary between the proglottids are studded with a row of interproglottid glands, which are yet undefined in terms of function.
The tapeworm, being monecious, contains both male and female reproductive organs in an individual. Thus each proglottid is a complete reproductive unit. Moreover, one defining feature of the genus is that there are two sets of reproductive organs situated at lateral sides with the associated cirrus pouches and genital pores in each proglottid. The testes are numerous.
Life cycle
The complete life cycle requires two hosts, ruminants as definitive hosts, and oribatid mitesOribatida
Oribatida , also known as moss mites or beetle mites, are an order of mites, in the "chewing Acariformes" clade Sarcoptiformes. They range in size from ....
as 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. Eggs are passed out from the intestine
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...
of the ruminant host along the gravid proglottids in the feces
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
into the soil. The eggs are eaten by soil mites
MITES
MITES, or Minority Introduction to Engineering and Science, is a highly selective six-week summer program for rising high school seniors held at the Massachusetts Institute of Technology. Its purpose is to expose students from minority, or otherwise disadvantaged backgrounds, to the fields of...
. Eggs must reach the gut of mite hosts within 1 day of release otherwise they are desiccated
Desiccation
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately sealed container.-Science:...
. However, chances of development is very good as soil mites can be so numerous on a pasture
Pasture
Pasture is land used for grazing. Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, cattle, sheep or swine. The vegetation of tended pasture, forage, consists mainly of grasses, with an interspersion of legumes and other forbs...
that even if only 3% are infected (with 4-13 cysticercoid
Cysticercoid
A cysticercoid is the larval stage of certain tapeworms, similar in appearance to a cysticercus, but having the scolex filling completely the enclosing cyst. In tapeworm infestations, cysticercoids can be seen in free form as well as enclosed by cysts in biological tissues such as the intestinal...
s each), a grazing ruminant may ingest over 2,000 cysticercoids per kilogram
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...
of grass. Once inside the intestine of mites, the eggs hatch and the oncospheres penetrate into the haemocoel and develops to the cysticercoid stage. This stage may take up to 4 months. When the infected mite is eaten by the grazing ruminants, mature cysticercoids are digested out of the mite, and develop into mature tapeworms in the small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
within 5–6 weeks.
Pathogenicity
M. expansa infections are generally harmless and asymptomaticAsymptomatic
In medicine, a disease is considered asymptomatic if a patient is a carrier for a disease or infection but experiences no symptoms. A condition might be asymptomatic if it fails to show the noticeable symptoms with which it is usually associated. Asymptomatic infections are also called subclinical...
, even when the tapeworms are present in large numbers in young lambs
Domestic sheep
Sheep are quadrupedal, ruminant mammals typically kept as livestock. Like all ruminants, sheep are members of the order Artiodactyla, the even-toed ungulates. Although the name "sheep" applies to many species in the genus Ovis, in everyday usage it almost always refers to Ovis aries...
. However heavy infection may cause intestinal obstruction, diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
and weight loss.
Diagnosis and treatment
DiagnosisDiagnosis
Diagnosis is the identification of the nature and cause of anything. Diagnosis is used in many different disciplines with variations in the use of logics, analytics, and experience to determine the cause and effect relationships...
is done by analysis stool sample in which eggs can be detected, or often observation of the gravid proglottids in feces and anus
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
.
Niclosamide
Niclosamide
Niclosamide is a teniacide in the anthelmintic family especially effective against cestodes that infect humans...
is most often used. 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....
is also 99–100% effective while albendazole
Albendazole
Albendazole, marketed as Albenza, Eskazole, Zentel and Andazol, is a member of the benzimidazole compounds used as a drug indicated for the treatment of a variety of worm infestations. Although this use is widespread in the United States, the U.S. Food and Drug Administration has not approved...
is 19-75% effective; and praziquantel + levamisole
Levamisole
Levamisole is an anthelminthic and immunomodulator belonging to a class of synthetic imidazothiazole derivatives. It was discovered at Janssen Pharmaceutica in 1966...
combination is very effective in reducing worm burden and improvement of weight.