As a medical biochemist I have learned a lot about parasites, mostly in humans, but it translates to most animals.
Cucurbitin is the chemical in pumpkin seeds that is supposed to provide the anti-parasitic action. The problem in controlled studies is that the amount of cucurbitin varies greatly even between the same pumpkin fruits from the same garden. So if it works, great. If not...
Other plant products said to have anti-parasitic action are beets, carrots, and raw garlic.
I have never found any studies of diatomaceous earth, taken internally, done by a reputable source. I believe it is well accepted that using DE on the ground will discourage the growth of parasites, as DE does dehydrate the exoskeleton. But I can't find scientific data to prove it works internally. The best data I can find suggests using it as 5% of your feed ration. So if it works, great. If not, ...