If there is a history of Marek's in your flock, no chicken, no matter what the age, is safe. All it takes is a stressful situation and Marek's will take hold. The age limit doesn't hold true. It is said that chickens are immune after 25 weeks of age...but, there are many of us that will tell...
I vaccinate everyone also. I just wanted to give you the information so that you would have it. I buy vaccinated or hatch and vaccinate...then booster at 6 weeks..then yearly. European countries follow this regimine and with all the problems I've been having, it sounds good to me :) Good...
Once they have been exposed, the vaccine is not as effective...but, if you do find out that it's Marek's, I would vaccinate anyway. Some studies have shown that it still helps to prevent the disease or, makes the symptoms less severe.
I'm still really concerned that this is Marek's. I've been dealing with this deadly disease for almost a year now. I've lost 30 + chickens...it never gets easier :( Try to treat for a vitamin deficiency. If she gets worse, I would have her put down and necropsied. Make sure you take care of...
I'm sorry to hear that your little girl is sick.
First, if she has been bleeding for three weeks, why haven't you started treatment? That being said, if it were coccidiosis, she would be dead by now. If you still want to try and treat, Corid is the medication of choice. You can find it in...