Identify the two Taenia species commonly causing human tapeworm infection and distinguish their proglottids and cysticercosis risk.

• A. Taenia saginata and Taenia solium
• B. Taenia asiatica and Taenia saginata
• C. Diphyllobothrium latum and Taenia solium
• D. Echinococcus granulosus and Taenia solium

Answer: (A)

Two Taenia species most commonly producing human tapeworm infections are Taenia saginata (beef tapeworm) and Taenia solium (pork tapeworm). Humans acquire them when they eat undercooked beef or pork containing cysticerci, respectively, and the adult worms develop in the intestine.

A key way to distinguish them is by looking at the proglottids. Taenia saginata proglottids are longer and contain many uterine branches—typically more than 15 up to about 30 or more—giving a segment with numerous branches. Taenia solium proglottids are shorter with fewer branches, usually around 7 to 13. This difference helps identify the species in examined proglottids or eggs.

Cysticercosis risk differs between the two. Humans can become intermediate hosts and develop tissue cysticerci (including neurocysticercosis) from Taenia solium if ingesting eggs shed in human feces. In contrast, Taenia saginata causes intestinal infection in humans, and humans are not a source of tissue cysticerci for this species; cattle are the intermediate hosts for saginata.