taenia

Taenia is a genus of parasitic flatworms in the class Cestoda and the family Taeniidae. Members are tapeworms that inhabit the intestines of vertebrate hosts as adults and use intermediate hosts to complete their life cycles. In humans, several species can serve as definitive hosts, with eggs shed in feces and spreading in the environment.

Morphology and life cycle: Adult Taenia have a scolex for attachment, followed by a chain of reproductive segments called proglottids. Proglottids and eggs are released in the host’s stool. In the environment, eggs or gravid proglottids are ingested by intermediate hosts such as pigs or cattle, where oncospheres develop into cysticerci in muscle tissue. When a definitive host consumes undercooked meat containing cysticerci, the parasite establishes an adult in the small intestine. Ingestion of Taenia solium eggs by humans can cause cysticercosis, a serious condition that may affect the brain, eyes, and other tissues; ingestion of cysticerci in meat leads to taeniasis.

Species and distribution: The most relevant human species are Taenia solium (pork tapeworm), Taenia saginata (beef tapeworm), and Taenia asiatica (Asian taenia). T. solium is found worldwide, T. saginata is widespread, and T. asiatica is reported mainly in parts of East and Southeast Asia. Transmission patterns depend on meat handling, cooking practices, and sanitation.

Clinical features, diagnosis, and treatment: Taeniasis is often asymptomatic but can cause mild abdominal symptoms. Cysticercosis, especially neurocysticercosis, can cause seizures and neurologic symptoms. Diagnosis relies on stool examination for eggs or proglottids, serology, and imaging for cysts. Treatment includes praziquantel or niclosamide for taeniasis, and albendazole or praziquantel for cysticercosis, often with anti-inflammatory therapy. Prevention focuses on proper cooking and meat inspection, sanitation, and measures to interrupt fecal-oral transmission.