Marek's paralysis can be as little as just one eyelid or pupil and paralysis is actually probably not the correct word..... it is more often a numbness or inability to coordinate a muscle, especially when they are under pressure like being jostled or bullied. So if they really concentrate they can sometimes activate that muscle. Yours also has a possible neck contortion (wry neck), which can be a symptom of several things including Marek's. In my experience with Marek's, very few get the skin lesions but there are a host of symptoms of the disease can cause that most birds do not get.
All that said, this chick is on the young side for Marek's and whilst it is technically possible, my gut feeling is that it is unlikely.
The other treatments you are giving are certainly worth a try although I would not give Poly-Vi-Sol at the same time as Corid if it contains the B1 Vitamin, Thiamine, so check the label.
As regards euthanizing, if you are able to offer supportive care and help feed the chick regularly, then I would keep going with it until it gets better or takes a turn for the worse. If it is unable to feed itself and you are unable to look after it due to life commitments, or it loses interest in food or shows signs of being in discomfort (cheeping) that you cannot easily fix (like pasty butt), that is when I would cull.
All that said, this chick is on the young side for Marek's and whilst it is technically possible, my gut feeling is that it is unlikely.
The other treatments you are giving are certainly worth a try although I would not give Poly-Vi-Sol at the same time as Corid if it contains the B1 Vitamin, Thiamine, so check the label.
As regards euthanizing, if you are able to offer supportive care and help feed the chick regularly, then I would keep going with it until it gets better or takes a turn for the worse. If it is unable to feed itself and you are unable to look after it due to life commitments, or it loses interest in food or shows signs of being in discomfort (cheeping) that you cannot easily fix (like pasty butt), that is when I would cull.
