chicks and our land

[countryjewel]

I have some 4 week old Wyandotte chicks, and we're going to be turning them out into the chicken tractor soon. I'm just wondering about the introduction to our land? Neighbors down the road lost a bunch of chicks a few years back when they turned them out into the run. Some went blind, others couldn't walk, it was horrible. Some people said it was something in our land, like a parasite perhaps? Lots of us have chickens up here and they're fine, maybe the concern is with new chicks who's relatives aren't from this land? Just wondering if anyone has heard of something like this? I'm hopefully putting the chicks in the tractor in a couple weeks, but I'm also concerned, and maybe I should vaccinate or something? Anyone have any advice would be great! Thanks