MrFluffyandGirls
Crowing
Here's a article that might be of help...
https://www.backyardchickens.com/articles/the-great-big-giant-mareks-disease-faq.66077/
https://www.backyardchickens.com/articles/the-great-big-giant-mareks-disease-faq.66077/
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Sorry about your silkie, but I alao think that he may have Mareks. They may display a numb leg with curled under toes as one of the possibly symptoms. It never hurst to offer some vitamin B complex or a vitamin that contains riboflavin (B2) just in case of a deficiency. A leg injury with nerve damage also could be possible. It is too late to vaccinate your other chickens, since they have been exposed. The vaccine takes 2-3 weeks to take effect, and it is best to vaccinate any new chicks to your flock while keeping them from any exposure to feather dander or dust around your coop and environment.
Here's a article that might be of help...
https://www.backyardchickens.com/articles/the-great-big-giant-mareks-disease-faq.66077/
I’ve tried to research and find somewhere that tests but not coming up with results.Really good article!!!
OP, if it were me, I would try and get him PCR tested if it were possible.