First off Lans, snakes don't forget how to kill. It would be like forgetting how to breath. It's instinct. They may not constrict because there's no need, but I find if I just tease my snake with the f/t mouse, it will grab and constrict. My largest snake hasn't eaten live since she was a hatchling and yet she still constricts every time I give her a frozen mouse. Next, parasites are not bacteria. Some bacteria is beneficial, but parasites aren't. Worms or protazoans aren't healthy for anyone. The benefits of feeding f/t certainly outweigh feeding live. If your snake eats f/t, stick with it.