Saw a YouTube video on it once. Tldr, the bad worms spread when an animal eats the meat of another infected animal. So, if you raise your pigs strictly vegetarian, they can’t catch that type of worm.
Also very strict testing and procedures, of course.



There would be, if people were able to understand the concept of single negation. But in practice, any single word answer to that question will likely lead to confusion or misunderstanding.