One of the best kept medical secrets in North America is that a majority of all native-born mexicans carry this parasite and actively spread it's eggs. They have a recognized innate resistance to it's effects but that does not stop them from being live carriers. Know about their habit of neglecting to wash their hands coming out of the bathroom? Some doctors think that behavior is the result of a neurotoxin secreted by these worms that causes their host to become careless about hygiene, in so doing proliferating that genetic flavor of worm for centuries in Mexico. These ideas are unpublishable in the mainstream press. Absolutely verboten.
Imagine what would happen if this information ever became widely disseminated.