Here is a presentation about Coccidia control in a kennel or shelter situation produced by Maddie's fund:

Coccidia are tiny single-celled parasites that live in the wall of your dog’s intestine. They are found more often in puppies, but they can also infect older dogs and cats.

Dogs become infected by swallowing soil that contains coccidia or other substances in the environment that may contain dog feces.

How will coccidia affect my dog?

Coccidiosis, the disease caused by coccidia, may not cause any signs in dogs but is usually more serious in puppies. The most common sign of coccidiosis is diarrhea. More severe infections can cause bloody diarrhea. Severe infections, especially in puppies, can kill them.

How do I prevent my dog from getting coccidia?

Coccidial infections can be prevented by removing your dog’s feces regularly from your yard or other areas where the dog goes to the bathroom. Because coccidia are found most often in puppies, it is important to have puppies examined for the parasite as soon as possible. Your veterinarian can perform a fecal test to diagnose coccidiosis. If your dog is infected with coccidia, your veterinarian is able to give it effective medications.

Can my cat get coccidia from my dog?

A dog infected with coccidia cannot pass the infection to cats and vice versa. Coccidial infections in dogs occur only by swallowing the coccidia in soil or dog feces.