so, i have a question - maybe two:
1) how is it possible that there is no natural way to deal with worms? are you suggesting that nature doesn't have a way to deal with this problem? without human superiority, all chickens would die from worms? let me go ahead and say i'm not engaging, or trying to start, a "fight". i'm sincerely curious.
2) how do you justify eating a bird, or an egg, after you've treated them with those chemicals? a horse wormer? you're eating what your chicken eats. i personally find that scary, and am interested in your response. i will openly admit, perhaps i'm not seeing the whole picture.
1. Most wild animals have parasites. In nature, the more an animal NEEDS to "replicate" itself (because of high rates of mortality / short lives) the more "babies" it has every year. Elephants--one every 2-1/2 years, sparrows: two clutches of 4-5 eggs each year. Lots of fledgling deaths, poor nests, high rate of adult deaths from predation. Wild ancestors of chickens couldn't be expected to have long lifespans as a whole, although there will be exceptions. No wild animals, and precious few domestic animals, get away without parasites if they live for long. The parasite load will vary with nutrition, infection rate, and general health. (I believe it was a parasitic infection that killed Elsa the lioness, from "Born Free.") 14% of all children on any playground have pinworm at any given time (more on some continents.) Isn't that a fun statistic? In stories about early North American settlement, you may read about children, particularly those of very poor farmers living in the south, going to school barefoot, malnourished, and sleepy, with dark circles under their eyes. This was anemia from hookworms picked up in pigpens; they burrow through the soles of the feet. Have you seen photos of people in Africa with absolutely ENORMOUS legs? It's elephantiasis; a microfilaria that clogs (the lymphatic system?) in the legs. (Nothing to do with elephants) More parasites on this earth than we can count, but most creatures, including us, die of something else before the parasite load gets us. Eating some things might decrease the load periodically; arsenic kills liver fluke (you get flukes from eating infected raw FRESHwater fish) but it can go either way. The worms flukes might die first, or you might go together. Same way in nature.
2. Watch your withdrawl periods. I don't know if poultry roundworms are the same, but mammalian roundworms can, with severe infestations, encyst in muscle and brain. Bears have a very high rate of trichinosis because of their diets (omnivore scavenger

that's why most people don't eat bear. Life is a juggling game. The most e-coli laden greens often come from little, and often organic, farms. So, you "pick your poison": buy from commercial growers that use more stringent guidelines, or from small places that don't use pesticides and chemicals, wash the dickens out of your produce, and smile. Something's going to get you sooner or later no matter what, but pesticides and defoliants and commercial farming practices are helping to destroy this earth. Cost to benefit ratio in decision making.
Just found a nice big roundworm in my pen today, and a ruffled up, unhappy banty. Sigh. I've been MEANING to order that Ivermectin pour-on...