Taenia saginata

Taenia saginata (synonym Taeniarhynchus saginatus), commonly known as the beef tapeworm, is a zoonotic tapeworm belonging to the order Cyclophyllidea and genus Taenia. It is an intestinal parasite in humans causing taeniasis (a type of helminthiasis) and cysticercosis in cattle. Cattle are the intermediate hosts, where larval development occurs, while humans are definitive hosts harbouring the adult worms. It is found globally and most prevalently where cattle are raised and beef is consumed. It is relatively common in Africa, Europe, Southeast Asia, South Asia, and Latin America. Humans are generally infected as a result of eating raw or undercooked beef which contains the infective larvae, called cysticerci. As hermaphrodites, each body segment called proglottid has complete sets of both male and female reproductive systems. Thus, reproduction is by self-fertilisation. From humans, embryonated eggs, called oncospheres, are released with faeces and are transmitted to cattle through contaminated fodder. Oncospheres develop inside muscle, liver, and lungs of cattle into infective cysticerci. T. saginata has a strong resemblance to the other human tapeworms, such as Taenia asiatica and Taenia solium, in structure and biology, except for few details. It is typically larger and longer, with more proglottids, more testes, and higher branching of the uteri. It also lacks an armed scolex unlike other Taenia. Like the other tapeworms, it causes taeniasis inside the human intestine, but does not cause cysticercosis. Its infection is relatively harmless and clinically asymptomatic. T. saginata is the largest of species in the genus Taenia. An adult worm is normally 4 to 10 m in length, but can become very large; specimens over 22 m long are reported. Typical of cestodes, its body is flattened dorsoventrally and heavily segmented. It is entirely covered by a tegument. The body is white in colour and consists of three portions: scolex, neck, and strobila. The scolex has four suckers, but they have no hooks.