Which seafood category is most implicated in foodborne illness and why?

• A. Molluscan shellfish
• B. Finfish
• C. Crustaceans
• D. Mammals

Answer: (A)

The key concept is how the biology of a seafood group affects illness risk. Molluscan shellfish—such as oysters, clams, and mussels—are filter feeders, which means they pull in and concentrate everything in the surrounding water. If the water is contaminated with pathogens or toxins, these shellfish accumulate them in high levels. When people eat them raw or undercooked, they’re exposed to those contaminants, leading to illness. Norovirus and Vibrio species are common culprits in shellfish-related outbreaks, and algal toxins can also accumulate in these filter feeders. Finfish and crustaceans can cause illness too, but outbreaks linked to molluscan shellfish are more frequent because of their filtration lifestyle and common practice of consuming them raw or lightly cooked. Mammals aren’t typical seafood choices in this context, so they’re less associated with seafood-related foodborne illness.