Hang on I have a whole rant on DE and why it DOES NOT WORK as an internal dewormer, and actually has a lot of drawbacks too. This is a subject I get rather heated about FYI
DE does NOT work as an internal dewormer!!!!
For DE to work, it needs to scratch the waxy outer layer on the bug's exoskeleton, which causes them to dehydrate and die.
With internal parasites, the environment is moist, so DE is ineffective, which BTW, is why it does not work as well with slugs in your garden. It only works when it's dry. It's important to understand how DE works to kill the bug. The scratches do not kill it, not directly. The DEHYDRATION resulting from the scratches does.
Other things to consider:
-edges on food grade DE are not as sharp as what's used in your garden, which further reduces it's effectiveness.
-quantity you'd need to feed could create digestive trouble
-irritates mouth, throat, lungs and GI tract
In the garden, it works fantastically! I could see it being effective for a more natural flea treatment in pets, however it can dry the skin, irritate eyes, throat and lungs (if inhaled)
I'm all about natural alternatives, I even feed my dog a raw diet.
However, I think there needs to be a balance between holistic and conventional medicine and this is one area that I think the chemical product is a much better choice, combined with regular fecal checks, good pasture management and only deworming as necessary.
Chemical Dewormers are Best