Diatomaceous Earth/DE cleanses parasites in animals.

Why are humans not taking Diatomaceous Earth as an intestinal parasite cleanser? This has been used in the feed of farm animals for ages. It is my understanding that calcined, or heated, Diatomaceous Earth, as that mined in Sweden, is not "natural" and reacts harshly like crystalline silica, unlike the "organic" silica product which is raw Diatomaceous Earth. Any clues here? Any info? Thanks.