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- Taenia saginata (beef tapeworm) and Taenia solium (pork tapeworm) are intestinal cestodes transmitted by ingestion of undercooked meat
- Epidemiology: T. saginata is the most common and most widely distributed human tapeworm, infecting 60 million people worldwide; endemic throughout Latin America, Africa, Central Asia and the Middle East. Less common in Europe and southeast Asia; uncommon in Australia and U.S.
- Life cycle:
- Eggs or gravid proglottids are passed in stool.
- Cattle ingest contaminated vegetation and oncospheres hatch in the intestine.
- Organisms invade the intestinal wall, migrate to striated muscles, and develop into cysticerci.
- Humans ingest raw or undercooked infected meat and gastric juices activate larvae, leading to evagination of scolex and attachment to the jejunum
- Over 2-3 months, cysticercus develops into an adult tapeworm; may grow up to 10 meters in length and live up to 25 years.
- Adults may have 1,000-2,000 proglottids, each containing tens of thousands of eggs, and a distinctive scolex with 4 disks.
- Eggs are spherical, thick walled, radially striated and measure 30-35 microns in diameter.