Which cestode is commonly transmitted to dogs via fleas?

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

Answer: (C)

This question hinges on how a tapeworm can reach a dog through an intermediate host, specifically fleas. Dipylidium caninum uses fleas as the intermediate host; the dog becomes infected by swallowing an infected flea during grooming or biting at it. The flea picks up tapeworm eggs from dog feces, develops them to the infectious cysticercoid inside, and when the dog ingests the flea, the adult tapeworm establishes in the small intestine. The worms shed proglottids that pass in feces and can look like tiny cucumber seeds on fur or in the stool.

Other cestodes have different transmission routes: Taenia taeniaeformis involves rodents as the intermediate host with felines as the definitive host, so fleas aren’t part of its life cycle. Echinococcus granulosus relies on eggs ingested from the environment and typically involves dogs as definitive hosts with livestock as intermediate hosts. Diphyllobothrium latum uses aquatic crustaceans and fish as its intermediate hosts. None of these rely on fleas for transmission to dogs.