Oh, just to add, anything he's poo'd on since being poorly will now be contaminated. You'll need to disinfect everything thoroughly with Jeyes fluid, and scrub your clean your carpets if he's poo'd on them. Do this all again 1 week into treatment and again when his treatment's finished. Also, he can't go back on any grass he might have poo'd on. It'll need to be dug up, and replanted with fresh turf or seed.
Do you have wildies in your garden? If so they're likely to be the cause of the problem. This means you'll have to keep your boy confined to one area of the garden that you've returfed, so invest in as large a run as possible. It's a shame if he's used to haveing free range outdoors, but otherwise you'll be back where you were.
Anyway, you don't know that it is Coccidiosis yet. Here's keeping fingers crossed it's not!