I don't think it would be an infection, because he has had it for at least a year. About the ivermectin, would the horse paste work, and how much should I give?
There could be 2 reasons your roo has yellow gunk in his ears. Ear mites or a respiratory infection. Gather up the following items you will need to clean and clear his ears: Eyedropper, neosporin, q-tips, tweezers, paper towels, a cup of warm water and hydrogen peroxide.
Tie your roo's legs together (not too tight,) then wrap an old towel around him snuggly. This will prevent him from squirming and flapping his wings when you lay him down on his sides.
It doesnt matter which ear you start on, he should be laying on one side. Take a q-tip and dip it in the water and clean the outside of his ear first, use as many q-tips as needed. The warm water softens the gunk and makes it easier to remove. Use a paper towel to clean around the area if necessary. There will be feathers covering his ear and it might be tough to see in the ear canal. You have to remove a little bit of the cotton from the tip of the q-tip to make it fit in the ear canal. Insert the q-tip slowly and gently into the canal and try to extract gunk...DONT go deep into the canal. Gently use tweezers to remove hardened gunk.
Grab your eyedropper and suck up some hydrogen peroxide, fill the ear canal with it. It will bubble up and loosen gunk free, this is normal.
Wait about a minute. Then remove abit of cotton from the tip of the q-tip (like before) and slowly and gently clean out the canal of gunk and the hydrogen peroxide, use as many q-tips as needed. Again, DONT go deep into the canal. After you're done, the ear will be clean.
Next, grab the neosporin and stick the tip gently into the canal and fill it up to the top til it comes out the ear. Do it slowly, you dont want the ointment spreading everywhere outside the ear. Now you are done with that ear. Flip your roo over and repeat this procedure for the other ear. Once your completed, remove the towel and untie his his legs and let him go about his business. He might shake his head some because he's not used to having his ears packed with ointment. But he'll be ok.
If there are mites, you should see tiny black or red specks on your q-tips or even see them in the ear itself. The neosporin will smother them if they're deep in the canal. You will have to repeat this procedure in 10 days if in fact it's mites.
If you didnt see mites, it could be a respiratory issue even though there wernt any other symptoms. Undue stress could set off other symptoms such as wheezing, runny nostrils, gurgling, swollen eyes etc...in which case you could seperate him and treat him with tylan.
You would also most likely have to repeat cleaning his ears out again a few months later, repeating the procedure I mentioned, IF it's a respiratory problem.
Keep in mind that ivermectin is a wormer, its secondary benefit is a miteacide. It would be ineffective if it's a respiratory issue you're dealing with in your roo.