This disease first appears in the form of poor laying skills and a weak chicken. As it progresses, you will notice coughing, sneezing, breathing problems, swollen joints, and possibly death.
Now, there is a vaccine for this illness, and it can be treated with an antibiotic from the vet. However, it can be picked up from other birds (even wild birds) and it can be transferred from a hen that has it to her chick through the egg.
As a precaution, keep an eye out for any of these symptoms so it can be treated quickly and effectively.