I had never heard of Coccidiosis until half my flock died. I went into the farm supply store and a lady told me that is what they had based on the treatment. She said it is soil born, or the germ gets into the soil in the area from the infected bird, and it will spread, and next time have them vaccinated. She also told me to call Auburn Department of Poultry Science at 334-844-2881 for questions, that she had lost her ENTIRE flock of teenage chickens to Coccidiosis and this poultry science department was very helpful. It is recommended you have your chickens vaccinated. Do not give up and get frustrated.
Some home remedies I have read about include adding 1 teaspoon or was it tablespoon??? of apple cider vinegar to each gallon of drinking water to get rid of it, I have also read to mix up one teaspoon of soil from the area your chickens are going to go live into each feeder full of baby chick crumbles. This is supposed to gradually build up the chicks immunity naturally to the germs in the area they will live. However, seems to me, if the illness is soil born it could possible give it to the baby chicks. I don't know. Hope all that helped in some way. Do not give up. Other people do it, you can too, you just have to stick with it. Don't get down about it.