Cysticercus (pl. cysticerci) is a scientific name given to the young

tapeworms 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, commonly known as tapeworms. Their bodies con ...

(larvae) belonging to the genus '' Taenia''. It is a small, sac-like vesicle resembling a

bladder The bladder () is a hollow organ in humans and other vertebrates that stores urine from the kidneys. In placental mammals, urine enters the bladder via the ureters and exits via the urethra during urination. In humans, the bladder is a distens ...

; hence, it is also known as bladder worm. It is filled with fluid, in which the main body of the larva, called scolex (which will eventually form the head of the tapeworm), resides. It normally develops from the eggs, which are ingested by the

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 ...

s, such as pigs and cattle. The tissue infection is called cysticercosis. Inside such hosts, they settle in the muscles. When humans eat raw or undercooked pork or beef that is contaminated with cysticerci, the larvae grow into adult worms inside the intestine. Under certain circumstances, specifically for the pork tapeworm, the eggs can be accidentally eaten by humans through contaminated foodstuffs. In such case, the eggs hatch inside the body, generally moving to muscles as well as inside the brain. Such brain infection can lead to a serious medical condition called

neurocysticercosis Neurocysticercosis (NCC) is a Parasitic disease, parasitic infection of the central nervous system, nervous system caused by the larvae of the tapeworm ''Taenia solium,'' also known as the "pork tapeworm". The disease is primarily transmitted ...

. This disease is the leading cause of acquired

epilepsy Epilepsy is a group of Non-communicable disease, non-communicable Neurological disorder, neurological disorders characterized by a tendency for recurrent, unprovoked Seizure, seizures. A seizure is a sudden burst of abnormal electrical activit ...

Discovery and naming system

Cysticercus was discovered in the late 17th century CE as a parasitic bladder worm. It was believed to be a different organism from the adult tapeworm (''

Taenia solium ''Taenia solium'', the pork tapeworm, belongs to the cyclophyllid cestode family Taeniidae. It is found throughout the world and is most common in countries where pork is eaten. It is a tapeworm that uses humans (''Homo sapiens'') as its definit ...

''), but still closely related to tapeworms for their similar-looking scolices. Hence, it was given a proper scientific name ''Taenia cellulosae'' in 1800 by German naturalist

Johann Friedrich Gmelin Johann Friedrich Gmelin (8 August 1748 – 1 November 1804) was a German natural history, naturalist, chemist, botanist, entomologist, herpetologist, and malacologist. Education Johann Friedrich Gmelin was born as the eldest son of Philipp F ...

. At the same time, another German, Johann Zeder, had created a new genus ''Cysticercus'' for a dog tapeworm. This genus was accepted for all bladder worms of ''Taenia''. It became a tradition to refer to the larvae of ''Taenia solium'' as ''Cysticercus cellulosae'', that of beef tapeworm ('' T. saginata'') as ''Cysticercus bovis'', that of sheep tapeworm (''T. ovis'') as ''Cysticercus ovis'', that of ruminant tapeworm (''T. krabbei'') as ''Cysticercus tarandi'', and that of the dog tapeworm ( ''T. crassiceps'') as ''Cysticercus longicollis''. Though this system of naming is now scientifically unacceptable, it is still widely used, particularly for description of the infections by the different species.

Structure

A cysticercus is a bladder-like transparent vesicle. It is composed of two main parts: the vesicular wall and a scolex. The vesicular wall is a complex structure made up of three distinct layers. The outermost is a smooth and undifferentiated layer called cuticular mantle. The middle is composed of cells that resemble epithelial cells. The innermost is made up of muscle and other fibres. Inside the vesicular wall is an invaginated (facing inward) scolex. The scolex contains suckers and hooks, and a neck attached to a rudimentary body segment.

Pathogenicity

In the normal life cycle of ''Taenia'', cysticerci develop in the muscles of the intermediate hosts such as pigs, cattle, and sheep. In these animals, they do not cause severe symptoms. They are transmitted to humans when their infected meats are eaten. However, ''T. solium'' is unusual because its cysticerci can develop in humans. Due to accidental consumption of the eggs from contaminated foodstuffs, cysticerci in humans produce clinical symptoms, cysticercosis. Thus, humans are accidental intermediate hosts.

References

{{Reflist, 30em Cestoda Larvae Parasitic animals of mammals