I have a flock of 60 mixed breed layers. Older chickens are 6 months to 2 years and were purchased with mareks vaccine. Twenty chicks are 8 to 12 weeks and not vaccinated. One chick showed signs of Mareks with leg paralysis 2 weeks ago and is quarantined. Placed hobbles on chick and adding B vitamins to feed. No change in condition of sick chick in 2 weeks. There is no design of disease in rest of flock. I have 2 questions: 1. How long should I should I wait to euthanize chick if no improvement? 2. If it is Mareks how long before it shows up in rest of flock?