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, known as tapeworms. Their bodies consist of ...

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

bladder The urinary bladder, or simply bladder, is a hollow organ in humans and other vertebrates that stores urine from the kidneys before disposal by urination. In humans the bladder is a distensible organ that sits on the pelvic floor. Urine enters ...

; hence, it is also known as bladder worm. It is filled with fluid, in which the main body of the larva, called

scolex 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 m ...

(which will eventually form the head of the tapeworm), resides. It normally develops from the eggs, which are ingested by the intermediate hosts, such as pigs and cattle. The tissue infection is called

cysticercosis Cysticercosis is a tissue infection caused by the young form of the pork tapeworm. People may have few or no symptoms for years. In some cases, particularly in Asia, solid lumps of between one and two centimetres may develop under the skin. Aft ...

. 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. This disease is the leading cause of acquired

epilepsy Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrica ...

Discovery and naming system

Cysticercus was discovered in the late 17th century CE as a parasitic bladder. 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 as its definitive host and pigs ...

''), 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. At the same time, another German, Johann Zeder, had created a new genus ''Cysticercosis'' for a dog tapeworm. This genus was accepted for all bladder worms of ''Taenia''. It became a tradition to refer to the larva 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 lifecycle 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, cycticerci in humans produce clinical symptoms,

. Thus, humans are accidental intermediate hosts.

References

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