Coughing chicken?

[sissybug]

I need some advice. I have had my road island red since December. She was already 1 1/2 years old. She was coughing at that time. I bought her some medicine you mix into the water. I gave that to her for 6 weeks. Cough went away but with in a few days it
Came back. So off and on I have been giving her the chick medicated starter. Her cough gos away and then
Comes right back. Not sure realy what to do for her. She eats great acts great but has a persistent cough. None of my other chickens are coughing at this time but I don't want any of them to start coughing with her. Help please. Thank you any advice is welcome!

 

[Eggcessive]

It could be caused by mold, an allergn, a virus, or a bacteria. I would get her tested for MG (mycoplasma gallisepticum,) which is a chronic respiratory disease. Tylan and oxytetracycline are commonly used to prevent it, while Denegard is used for recurrent infections. It is contagious and can make carriers of the flock. Here is a link for testing centers, and your vet may be able to do it:
http://www.aphis.usda.gov/animal_health/nahln/downloads/all_nahln_lab_list.pdf

Here is a good link about the most common respiratory diseases with symptoms:
http://edis.ifas.ufl.edu/ps044