The tapeworms or cestodes, are ribbon-shaped segmented worms which inhabit the intestinal tract of many vertebrates (including humans). most tapeworm infections occur in Africa, yugoslavia, the middle East, Southeast asia, Mexico and parts of south America and the U.S.S.R. Some forms may be contracted (in the U.S.) from infected dogs or cats (more common in children) by ingestion of infected fleas. Taenia solium (pork tapeworm) is occasionally encountered in the united states today in immigrants or visitors from endemic areas. Taenia saginata (beef tapeworm) is seen more often, especially in those who consume raw beef. Some tapeworms have been known to live up to 20 years and exceed 10 metres in length. Often asymptomatic infestations, but unexplained weight loss, symptoms of pernicious anaemia and the presence of white eggs or ribbon-like segments of worm in stools can be seen in some.