I agree birds will pick up worms even if raise on wire......main reason other bugs are host to the worms.
I use both safe guard and ivomec....Wazine is a waste only kills round worms......which safe guard does...ivomec kill worms ,mites ,and lice.
beetle,earwigs,grasshopper,earthworm,slug,snail,termite,dragonfly,and mayfly all can be host to parasitic worms.
Yes chicken eat most of these...if on the ground or freerange ,they will pick up more like earthworms, but reason why everyone should worm their birds...depend on your location some more than others.
I quit using ivermectin long ago. It has lost its effectiveness as a wormer in chickens most likely as overuse as a treatment for mites. It wont kill lice in chickens, lice dont suck blood like mites. However, ivermectin is still effective killing mites. Here's a link regarding ivermectin's ineffectiveness in large roundworms, cecal worms and capillary worms in chickens:
I bought some lice infested birds a couple of years ago and used Ivermectin as the only treatment. The lice were gone within 48 hrs.
I use it on all my birds........you will not any on any of my birds...i use the pour on for cattle. 1 cc on peafowl size birds.