Which tapeworm is the flea-transmitted parasite of dogs?

• A. Diphyllobothrium latum
• B. Dipylidium caninum
• C. Taenia taeniaeformis
• D. Echinococcus granulosus

Answer: (B)

The flea-transmitted tapeworm of dogs is Dipylidium caninum. The key idea is that this parasite relies on an intermediate host—an infected flea. Dogs become infected when they swallow a flea during grooming or biting, and the cysticercoid stage inside the flea develops into the adult tapeworm in the dog's intestine. The worm then produces proglottids that are passed in the feces, and these proglottids (often seen as cucumber-seed–like packets) reflect this flea-mediated life cycle.

Diphyllobothrium latum is a fish tapeworm and is acquired by eating raw or undercooked fish, not through fleas. Taenia taeniaeformis involves cats as the definitive host with rodents as intermediate hosts, not fleas. Echinococcus granulosus involves eggs shed in dog feces and typically livestock or humans as intermediate hosts, again not through fleas.