Diphyllobothrium latum infection is typically acquired through the consumption of which type of food?

• A. Raw vegetables
• B. Contaminated water
• C. Under-cooked fish
• D. Dairy

Answer: (C)

Diphyllobothrium latum infection is transmitted when people eat raw or undercooked freshwater fish that contain plerocercoid larvae. The parasite’s life cycle uses fish as the intermediate host, so the human gets infected by consuming fish in this state, not by eating vegetables, drinking contaminated water, or consuming dairy. Cooking fish thoroughly kills the larvae, preventing infection. In some cases the worm can cause vitamin B12 deficiency leading to anemia, which helps explain why this particular food-borne route is characteristic of this tapeworm.