Is Corid a brand name? I've never used anything like ti and I'm not sure I'd know a case of Cocci if I had one. I worm as a precaution and use DE regularly when cleaning for mites if there ever are any. I can't really say I've noticed them either.I agree with Eggcessive. I use Corid when a rare case of cocci pops up in chicks during a protracted wet period. It is amprolium, a thiamine analog. It messes with the B vitamin that the oocysts that cause cocci feed off of and you only give it for 5 days. Not an antibiotic at all. I've never needed to treat adults, though. Usually, by 12 weeks they are immune to the varieties that are in their soil and unless exposed to a new strain they've never encountered, they shouldn't fall prey to it as adults. I suppose it could happen when the immune systems are severely compromised, as with Marek's or other serious diseases.
I have heard of people breeding for resistance to cocci, however, those are some hard and, to me, truly unnecessary losses since they do develop natural immunity even if treated for a bout of it as chicks.
Truth? I have a sick pullet. Not one from my lines. I got hatching eggs and it's one of them. I don't know what is wrong and it's just her.
Usually if I lose a bird it's just one that presents or I find dead with no visible symptoms. Not often mind you.