Bot eggs????

Yesterday I saw yellow spots on my horse's legs and I just thought it might be small pieces of hay. Then today I saw that they were still on him, so I razored the bots of his legs in the pasture. I TOTALLY FORGOT to put the bot eggs in a plastic bag, so now there somewhere in his dirt pasture ( I just tilled it ). So I was wondering will he be OK? I deworm him about every two months so..... Also how do they get bot eggs,and is there a way to precent them. I feel like a fool that I forgot the plastic bag :( :( Will my baby be alright?