• Tapeworms cause two major types of zoonotic disease syndromes, depending on whether humans are the definitive or intermediate host.
  • When humans serve as definitive hosts, adult tapeworms infect the GI tract and interfere with nutrition; patients may be asymptomatic.
  • When humans serve as intermediate hosts for the larval cestode, serious pathology results.
  • Causative organisms include the following:
    • Taenia saginata (beef tapeworm)
    • Taenia solium (pork tapeworm)
    • Diphyllobothrium latum (fish tapeworm)
    • Dipylidium caninum (dog tapeworm)
    • Echinococcus granulosus


  • Beef tapeworm
    • Estimated 77 million people infested worldwide
    • Widespread in cattle-breeding areas of the world; endemic in Asia, Latin America, Eastern Europe
  • Pork tapeworm
    • Estimated >50 million people infested worldwide
    • Taeniasis: typically asymptomatic infection with adult tapeworm (from undercooked pork)
    • Cysticercosis: infection with larval parasite (fecal–oral transmission from carriers)
    • High prevalence in developing areas of Asia, Central and South America
    • Up to 5,000 new cases of neurocysticercosis in United States annually
  • Fish tapeworm
    • Infection is most prevalent in temperate climates of Europe (Finland, Estonia, Sweden most common) and Canada.
    • Persons who prepare or eat raw freshwater fish are most at risk.
    • In the United States, infected salmon have been implicated in most cases.
  • Dog tapeworm
    • Found in dogs and cats worldwide
  • Echinococcosis
    • Associated with the practice of feeding sheep viscera to dogs
    • Hyperendemic in sheep-raising areas of South America, Australia, areas of Africa, China, Central Asia, and the Western United States


  • Adult tapeworms
    • Proper cooking prevents transmission of beef, pork, and fish tapeworms.
  • Pork tapeworm
    • Storage of pork for 4 days at −5°C (21.2°F) or 1 day at −24°C (−11.2°F) kills most cysticerci.
    • Persons traveling to areas with high endemic rates of cysticercosis should avoid eating uncooked vegetables and fruit that can’t be peeled.
  • Fish tapeworm
    • Brief cooking (at >56°C [132.8°F] for 5 minutes) or freezing (−18°C [−0.4°F] for 24 to 48 hours) renders the fish safe to consume.
  • Dog tapeworm
    • Periodic deworming of pets
  • Echinococcosis
    • Careful disposal of sheep viscera and mass chemotherapy of dogs can interrupt the life cycle of E. granulosus as the cestode moves between sheep and carnivore hosts.


  • Beef tapeworm
    • Cattle (intermediate host) ingests T. saginata eggs in contaminated feeds. The eggs hatch, releasing embryos which penetrate intestinal mucosa, enter the bloodstream, and settle in skeletal muscle, where they develop into larvae. Larvae in undercooked meat are consumed by humans and mature into adult tapeworms within the human (definitive host) GI tract.
  • Pork tapeworm: Humans are the only definitive host for the adult pork tapeworm. Both humans and pigs are intermediate hosts for its embryonic form, cysticercosis.
    • Pigs ingest T. solium eggs. In the intestine, the eggs release embryos that penetrate the mucosa, enter the bloodstream, and settle in various tissues to differentiate into cysticerci (infective larvae). Cysticerci are ingested by humans (definitive host) who consume undercooked pork.
    • Humans ingest food contaminated with human feces containing T. solium eggs. The eggs hatch, liberating embryos which penetrate the intestinal mucosa leading to blood-borne distribution to the brain, subcutaneous tissues, muscle, and eye, where they develop into cysticerci.
  • Fish tapeworm
    • When sewage containing D. latum eggs contaminates freshwater lakes and streams, eggs hatch into the water becoming embryos. Embryos are eaten by crustaceans and then passed on to fresh water fish. Humans are infected when they consume these undercooked fish. The larvae mature into adult tapeworms in the intestines of humans in 3 to 5 weeks’ time and can survive up to 10 years. Rarely, the tapeworm migrates thru intestinal wall to other tissues (sparganosis).
  • Dog tapeworm
    • Larvae develop in fleas (intermediate host) after ingestion of the eggs; humans are infected through accidental ingestion of infected fleas.
  • Echinococcosis (hydatid disease)
    • Humans ingest eggs of E. granulosus through contaminated dog feces. After ingestion, the eggs hatch and release embryos (oncospheres) in the small intestine. Penetration through the mucosa leads to blood-borne distribution to the liver, lungs, and other sites, where development of cysts begins. Within the cysts, new larvae (scolices) develop, accumulate fluid, and encroach on surrounding structures.

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