Is it gapeworm?

[Abwgnr12]

My chicken is having trouble breathing, stretching out her neck, mouth wide open, strange sound. Wasn’t eating and drinking. I went to Facebook and many people thought gapeworm or respiratory. I gave her .25ml of duramycin as someone has recommended, 1x every other day, for 5 days. She got the first does Monday and will get the 2nd and 3rd Wednesday and Friday. Do you believe this is the right treatment? She seemed better most of the day Tuesday, quiet and less arranged breathing, but then late tonight (Tuesday) she’s back to the strained breathing. Please advise!

 

[nuthatched]

Gapeworm is very, very rare.
What other symptoms? Mucus? Sneezing? What does the crop feel like?
There's also a possibility of a crop issue, that's why shes adjusting her crop.

 

[Wyorp Rock]

Welcome To BYC

Can you post a video of her actions? Upload video to YouTube and provide a link.

How old is she?
What do you feed, including treats?
How long have you had her?
Where are you located in the world?
Is her crop emptying overnight?
Have you noticed any symptoms like bubbles in the eyes, mucous, coughing/sneezing, yellow or white pasty material or lesions inside the beak, a bad odor coming from around her head or on her breath, lice/mites, facial swelling, infection in the ears, bloat or fluid in the abdomen below the vent between her legs?

Is the Duramycin injectable? How much does the hen weigh? Duramycin (Oxytetracycline) may help with respiratory disease like Mycoplasma or some other infections, but the dose is hard to nail down, but it looks like you may not be giving the correct dose - here's the best info I have on dosing https://www.backyardchickens.com/threads/miracle-la-200-dosage-and-vetrx-for-crd-treatment.631458/

If you are unable to get video, if you have photos of her you can share that would be good too. Get one of her poop as well.

Work on hydration and keep her eating. Gapeworm is not that common, getting a fecal float is always a good idea, but if she's in dire straits and the antibiotic is not helping (once you are sure she's getting the proper dose), then treating with Valbazen or Safeguard may be worth a shot.