They run across the back of our pasture....where the mares are turned out every day. They were there when we had no problems ... abortions ... They were there when we had abortions, they are there since we removed the black walnut trees and this year had a phenominal foaling season. So, I don't think they have caused us any problems.
This was investigated when we were having late term abortions, but no connection was ever found. It turned out to be the black walnut trees.
Charlotte