Cysticercus
Cysticercus (pl. cysticerci) is a scientific name given to the young
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), 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.[3] 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.[4][5] Though this system of naming is now scientifically unacceptable, it is still widely used, particularly for description of the infections by the different species.[6]
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.[1][7]
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.[8][9] 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.[10]
References
- ^ ISBN 978-0-85199-839-8.
- S2CID 13683438.
- ISBN 978-90-265-1513-2.
- ISBN 978-0-12-391605-1.
- ^ "List of all parasites". Faculty of Tropical Agrisciences. Czech University of Life Sciences. Retrieved 5 May 2017.
- S2CID 1492078.
- S2CID 20310143.
- PMID 26252878.
- PMID 4559145.
- PMID 12932389.