Need help: 16 week old Orp not walking well, sits all day.

[TattooedMama]

So my Blue Orpington is 16 weeks old now (whom we believe is a hen but we are watching closely, lol). I have noticed her sitting more often lately the past week or so and thought it was odd. She would walk around if you got close to her and seemed to walk fine. Two days ago we went to the store and when we came back my son said she was walking funny. She seems to have trouble putting weight on one of her legs. Sometimes she will walk fine for a few minutes at a time but then she will favor one leg over the other and walk funny. When she sits, its not graceful at all. I brought her into the house and put her in a dog crate with probiotics and electrolytes in the water and gave her some food. She has been eating and drinking but she sits when she does, like she cant handle standing for long periods. She also seems to be favoring her left side and only peck that direction, I remember last night reading something about loss of neck control? When she continues to peck to the left, it throws off her balance and she starts to roll. She can turn her head right but doesn't when eating.

She shares a pen with two chocolate hens and one chocolate roo. The other birds are all fine. I have had this blue hen since she was 8 weeks old and shes never appeared to have any problems. These four were my first set of birds on my property and they come from a knowledgeable local ranch. I did get a set of day old chicks in the mail almost 5 weeks ago now but those are vaccinated against Mareks and in a brooder inside the house, very separate from my older babies who are outside. She also seems to not be holding one of her wings close to her side? There are no obvious injuries that I can see. Any ideas? And should I just count on her not making it?

 

[Eggcessive]

I would suspect some neurological disease such as Mareks disease or lead poisoning, but mycoplasma synoviae and viral arthritis can cause a chicken to sit on it's hocks. Is there any swelling of her leg or foot joints? Any respiratory symptoms? Here is some reading:
https://www.backyardchickens.com/a/the-great-big-giant-mareks-disease-faq
http://extension.unh.edu/resources/files/Resource000791_Rep813.pdf
http://partnersah.vet.cornell.edu/avian-atlas/search/disease/502
http://www.thepoultrysite.com/diseaseinfo/99/mycoplasma-synoviae-infection-ms-infectious-synovitis

 

[TattooedMama]

I would suspect some neurological disease such as Mareks disease or lead poisoning, but mycoplasma synoviae and viral arthritis can cause a chicken to sit on it's hocks. Is there any swelling of her leg or foot joints? Any respiratory symptoms? Here is some reading:
https://www.backyardchickens.com/a/the-great-big-giant-mareks-disease-faq
http://extension.unh.edu/resources/files/Resource000791_Rep813.pdf
http://partnersah.vet.cornell.edu/avian-atlas/search/disease/502
http://www.thepoultrysite.com/diseaseinfo/99/mycoplasma-synoviae-infection-ms-infectious-synovitis

HE seems to be fine. Wouldn't you know he decides to crow for the first time sitting next to me in my office. He does have his mouth open slightly on and off but I figured that was because it is somewhat warm in the house. Thermostat is at 78 but this room tends to get warmer. It is definitely his left foot that he's having trouble walking on. I don't see any obvious swelling or difference in the legs.

 

[TattooedMama]

I should also add, he does not have diarrhea and his pupils are perfectly fine. He is not missing food when he aims to peck at it, has eaten a good amount and he's drank a fair amount of water since yesterday. He even seems alert. I'm wondering if it's possible that he is leaning so far to the left because he can't put pressure on that foot and is trying to maintain balance. He will revert from favoring his right leg to walking pretty well.