While accidental tapeworm infections in developed countries are quite rare, such infections are more likely to occur in countries with poor sanitation facilities or where food hygiene standards are low. History and culture
In ancient Greece, the comic playwright Aristophanes and philosopher Aristotle described the lumps that form during cysticercosis as "hailstones". In Medieval times, in The Canon of Medicine, completed in 1025, the Persian physician Avicenna recorded parasites including tapeworms. In the Early Modern period, Francesco Redi described and illustrated many parasites, and was the first to identify the cysts of Echinococcus granulosus seen in dogs and sheep as parasitic in origin; a century later, in 1760, Peter Simon Pallas correctly suggested that these were the larvae of tapeworms.Tapeworms have occasionally appeared in fiction. Peter Marren and Richard Mabey in Bugs Britannica write that Irvine Welshs sociopathic policeman in his 1998 novel Filth owns a talking tapeworm, which they call "the most attractive character in the novel"; it becomes the policemans alter ego and better self. Mira Grants 2013 novel Parasite envisages a world where peoples immune systems are maintained by genetically engineered tapeworms. Tapeworms are prominently mentioned in the System of a Down song "Needles": their inclusion within the song result in a lyrical dispute among band members.There are unproven claims that, around 1900, tapeworm eggs were marketed to the public as slimming tablets. A full-page coloured image, purportedly from a womens magazine of that period, reads "Fat: the enemy ... that is banished! How? With sanitized tape worms. Jar packed. No ill effects!"
There are four longitudinal collection canals, two dorso-lateral and two ventro-lateral, running along the length of the worm, with a transverse canal linking the ventral ones at the posterior of each segment. When the proglottids begin to detach, these canals open to the exterior through the terminal segment.The main nerve centre of a cestode is a cerebral ganglion in its scolex. Nerves emanate from the ganglion to supply the general body muscular and sensory endings, with two lateral nerve cords running the length of the strobila. The cirrus and vagina are innervated, and sensory endings around the genital pore are more plentiful than in other areas. Sensory function includes both tactoreception (touch) and chemoreception (smell or taste). Proglottids
Once anchored to the hosts intestinal wall, tapeworms absorb nutrients through their surface as their food flows past them. Cestodes are unable to synthesise lipids, which they use for reproduction, and are therefore entirely dependent on their hosts.The tapeworm body is composed of a series of segments called proglottids. These are produced from the neck by mitotic growth, which is followed by transverse constriction. The segments become larger and more mature as they are displaced backwards by newer segments. Each proglottid contains an independent reproductive tract, and like some other flatworms, cestodes excrete waste through flame cells (protonephridia) located in the proglottids. The sum of the proglottids is called a strobila, which is thin and resembles a strip of tape; from this is derived the common name "tapeworm".