When one of ours started a black scour the vet suggested cocci, it was abit early for nemo so he gave, sold, us an injection for him. It cleared up so we bought a small bottle of Vecoxan drench and have done others when they show signs. It seems the problem for us is that we turn all the lambs out into the same field, the older ones are fine as they gain immunity before they consume too many but the younger ones pick up a lot more due to the older ones passing the eggs, not eggs I know but I can't spell ooocists. We treat them as we see a dirty bum, they dry up virtually over night.
Next year I am going to try the Tubbies buckets, they contain an anticocidiostat and seem to solve the problem, perhaps I can persuade the ewes to lamb closer together.