- Taenia saginata (beef tapeworm), Taenia solium (pork tapeworm), Taenia asiatica (pork tapeworm), and Taenia hydatigena (canid tapeworm) are intestinal cestodes.
- All Taenia species can cause tapeworm infection of the human intestine (Taeniasis) by ingesting larvae in undercooked meat.
- T. saginata does NOT cause cysticercosis.
- T. solium is the primary cause of human cysticercosis by ingesting proglottids or eggs through fecal-oral transmission; T. hydatigena can also cause human cysticercosis.
- T. saginata is the most common and 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 the U.S., but epidemiology may shift with increased global migration.
- Life cycle:
- Eggs or gravid proglottids are passed in the 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 the evagination of scolex and attachment to the jejunum.
- Over 2-3 months, cysticercus develops into an adult tapeworm; it may grow up to 10 meters long and live up to 25 years.
- Adults may have 1,000-2,000 proglottids containing tens of thousands of eggs and a distinctive scolex with 4 disks.
- Eggs are spherical, thick-walled, and radially striated, measuring 30-35 microns in diameter.
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