As a medical biochemist who works in a medical lab, I have seen lots of worms in my time, both from humans and animals. Personally, if I have any reason to believe that any of my animals (dogs, cats, chickens) have worms (get in the habit of watching stools) I take a fecal specimen with suspicious stuff to my vet for testing. Be sure the specimen is fresh (within the last hour and transport with ice or a cool pack in hot weather) or keep refrigerated until you can get it to the vet within a few hours. The vet can tell you what kind of parasites are present and which medication will eradicate the problem.
I have read quite a bit of the info on pumpkin seeds, DE, etc and I'm not convinced on its effectiveness. Any medication you use will require a withdrawal period (I usually use two weeks after the last dose as my standard since many meds have not been tested on chickens but vets know what works, pharmaceutical companies are just not going to test the meds on EVERY species of animal as the testing is too expensive).
Since I live in a VERY dry region that does not bode well for most parasites I have very little risk with my animals. But if I lived where parasites are a routine thing I would certainly think about collecting stool specimens every 3-6 months for testing and proceed accordingly with treatment.
