IUCN threat status:

Not evaluated

Brief Summary

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Brief Summary

The cestode Taenia solium (pork tapeworm) (along with T. saginata [beef tapeworm] and T. asiatica [Asian tapeworm]) causes intestinal taeniasis in infected humans, which serve as the definitive host (i.e. the host that harbors adult parasites). Taenia solium can also cause cysticercosis, which results when a human serves as an intermediate (and dead-end) host. Taenia solium (like T. saginata) has a worldwide distribution (T. asiatica is limited to Asia). Taenia solium is more prevalent in poorer communities where humans live in close contact with pigs and eat undercooked pork. Taeniasis and cysticercosis are very rare in Muslim countries. It is important to note that human cysticercosis is acquired by ingesting T. solium eggs shed in the feces of a human T. solium tapeworm carrier and thus can occur in populations that neither eat pork nor share environments with pigs. (Centers for Disease Control Parasites and Health website)

Humans are the only definitive host for Taenia solium (as well as for T. saginata, and T. asiatica). An infection usually involves just a single tapeworm (Nakao et al. 2010). Eggs or gravid proglottids (bisexual reproductive segments) are passed with feces; the eggs can survive for days to months in the environment. Pigs typically become infected by ingesting vegetation contaminated with eggs or gravid proglottids. In the animal's intestine, the oncospheres hatch, invade the intestinal wall, and migrate to the striated muscles, where they develop into cysticerci. A cysticercus can survive for several years in the animal. Humans become infected and develop intestinal taeniasis by ingesting raw or undercooked infected pork. In the human intestine, the cysticercus develops over several months into an adult tapeworm, which can survive for years. The adult tapeworm attaches to the small intestine by its scolex and resides in the small intestine. The length of an adult T. solium is typically 2 to 7 m. The adults produce proglottids which mature, become gravid, detach from the tapeworm, and migrate to the anus or are passed in the stool (several per day). Taenia solium adults have an average of 1,000 proglottids and each proglottid produces around 50,000 eggs. The eggs contained in the gravid proglottids are released after the proglottids are passed with the feces. (Centers for Disease Control Parasites and Health website) Disease can take another form if a human ingests eggs present in food or water contaminated by the feces of human tapeworm carriers. In this case, the human can become an intermediate (and dead-end) host and harbor the cystic stage in its tissues, causing cysticercosis and, if there is neurological involvement, neurocysticercosis. (Michelet et al. 2010 and references therein)

Up to 20 million people are infected with Taenia solium cysticerci worldwide. Furthermore, neurocysticercosis is a major cause of adult onset seizures in many low-income countries and accounts for 50,000 deaths each year. Domestic pigs (Sus scrofa), African wild pigs (Potamochoerus), and other animals including primates, dogs, rabbits, and hyraxes (family Procaviidae) serve as the main intermediate hosts. (Michelet et al. 2010 and references therein)

Conlan et al. (2009) explored the role of interspecific competition among Taenia species in modulating T. solium infection of humans. In Southeast Asia, T. solium faces competition in both the human definitive host and the typical pig intermediate host. In humans, adult T. solium, T. saginata and T. asiatica compete through density-dependent crowding mechanisms. In pigs, metacestodes of T. solium, T. hydatigena and T. asiatica compete through density-dependent immune-mediated interactions. Humans are the definitive host for T. solium, T. saginata and T. asiatica. Pigs are the known intermediate host for T. solium, T. asiatica, and T. hydatigena. Canines are the definitive host for T. hydatigena and bovines are the intermediate host for T. saginata. Conlan et al. (2009) compared the biological characteristics of T. solium, T. saginata, T. asiatica, and T. hydatigena. (Conlan et al. 2009 and references therein)

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Source: EOL Rapid Response Team

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