Chickens can gape with respiratory infections such as ILT, MG, and others, but gapeworm and a stuck foreign object in the throat can also cause gaping. Chickens with gapeworm cannot eat or drink due to the difficulty breathing. But gapeworm is fairly rare. The sneezing kind of makes it more likely to have a respiratory infection. Do you see any nasal drainage, watery eyes, rattles or wheezes? What antibiotic did the vet decide on? Let us know how is getting along, and I would probably worm him with some Safeguard liquid goat wormer 1/4 ml per pound for 3 days in a row, given orally. That would treat gapeworm.
Edited by Eggcessive - 12/19/15 at 6:48pm