Cocci is a really common parasite and it seems like a lot of farm folk who keep other livestock besides rabbits are routinely treating for it. I think its super common for chickens and goats to get it and if you go to any farm store you always see Cocci medications lining the shelves. Also, read that wild birds can have it and poo on grass and rabbits can pick it up from that. But, I think if you do not live near any farm animals, your rabbits are probably pretty safe though. I live in New Zealand, no predators, so I let my rabbits graze in my backyard and they have never gotten cocci (knock on wood).