If parasitized oysters are eaten raw, there is a risk of parasitic infection. If parasitized oysters are cooked thoroughly, they are generally not infected with parasites. Parasites are organisms that need to attach to another organism to survive and can be categorized into three main groups: worms, ectoparasites and protozoa. Oysters may be parasitized by worms or protozoa, and if you eat raw oysters, you are likely to be infected with parasites. However, if raw oysters are thoroughly cooked, the parasites in them will also be killed by high temperature and will not have the ability to become infected. In addition to oysters, it is generally recommended that frogs, crabs, fish, shrimp, water chestnuts, wild rice and other aquatic products should be thoroughly cooked before eating to avoid the risk of parasitic infection. “Thoroughly cooked food is safe.”