Coccidia are microscopic, single celled parasites that infect the intestinal tract. They can cause Coccidiosis, which is an infection often accompanied by diarrhea (often bloody) and lethargy. Weight loss and crop issues are also sometimes noted. This can be diagnosed through a fecal float by a vet. Coccidiosis is most common in chicks around "brooder age". Week old to 7ish weeks. Older birds can get it, it's just much less common.
Marek's is a viral disease caused by the Herpes virus. There are different types of Marek's: Ocular, cutaneous, neural, and visceral. The form most people experience is neural. Symptoms include limping, and then paralysis of usually one leg. Sometimes sudden onset paralysis of one leg. Sometimes that progresses to both legs. Lethargy, weight loss, seizures, and crop issues have also been known to follow. This can only be diagnosed through necropsy by a state AG vet. Marek's is most common is birds 12-30 weeks of age. I've never personally seen it affect younger than 12 weeks. I have seen it affect ages up to about a year.
I have been doing as much research as possible but can’t find anything describing significant differences.. please help
