This is partially incorrect. Even if a parasite did mutate, it would be a single strand of it, not magically all of them at once. For that, we could easily pass regulations and tests to make sure things we consume or other things would not infect us with that strand. On the other hand, why would it be a zombie-like apocalypse? It wants to reproduce in the large intestines of cats, would it mean that people would just want to be around cats more often? What if a strand of the parasite has already mutated, but only infects women who knit?