kakayona-from what I understand and from my experience, blood in stool is one sign but all may not get it, especially chicks under 3 weeks may not. Mine were very lethargic, not eating/drinking much. Some would stand by themselves and sorta sway and sleep on and off. Their feathers look unkempt, but mostly just the being super sleepy. One day old chicks will be sleepy, but mine are 1-3 weeks and were doing great, annoyingly loud and happy chirping eating and drinking sleeping then scratching around-and all of sudden all the activity just stopped. BUT-coccidosis comes from the soil so in very young chicks it might not be if they have had no contact with soil, but you have to remember soil from your shoes, hands, the kids hands or that cute free range they went on for only 10 minutes!