shepard mix losing all hair around neck and on tail

8 yr old male.  started as if his collar was rubbing the hair off.  Now  is 4 to 5 inches wide covering the whole back and side areas of his neck.  His hair is dry and matts easily.  Lost weight but appetite is still excellent.  He had a full tail that is now almost bare of hair and you can raise his hair up in many areas on his head and back and find huge bald spots.  His bald skin on his neck has turned black.  His whole belly is black but no hair loss there.  We  have him on thyroid meds for 4 or 5 weeks.  No change but what hair he has seemed to get softer.  Did an ultra sound and found nothing.  His skin seems dry.  He itches sometimes but really not much.  Acts as if he is sensitive when I brush him.

Had changed his food a year ago to a salmon because of a diarreah (diarrhea) so changed it back to what he was used to before the hair loss started.  Put his weight back on quickly but No change in in hair loss in 3 months.  He's same in his behaviors.  Does not act at all sick.

Any ideas would be greatly appreciated.

[ggreg]

Obviously your vet needs to check for a mange-like skin disease, they take samples and look at them under a microscope.  Then they give medicine to get rid of it, as well as sometimes special medicated shampoos.  If you do nothing else, do that.

I might mention that getting the thyroid medication dose right is challenging, so you need to get a second opinion on not only how much, but even if it's needed at all.

I'm glad you switched back to the old dogfood, keep him on it.  If you ever have a problem with dogfood again, we used to use Nutro with ours and it made their coats look fantastic.  If the skin samples do not show a skin disease, then you might consider a different kind of flea deterrent... we have our dogs on Revolution, never had a problem with fleas ever again with that stuff.  Lastly, occasionally hair loss happens when a dog doesn't have enough to do in the day, so if you aren't already, you gotta get a ball and throw it for your dog every day and provide him with a Nylabone... when dogs get some age on them, they are not as frisky, but they do get bored, thus the need for some form of entertainment.

[ginger899]

I was thinking Mange too...(?) This is easily picked up from open countryside, or even gardens and yards where any wild creatures can go. Once my other dog got mange. The vet said it was fox-mange (very common in my area)

Sarcoptic Mange is caused by a tiny mite. What made me wonder if this could be the case for your dog is it started under his collar. That would be a perfect hiding-place and breeding-ground for the mange-mite. Also it is classic for hair around the affected area to become very dry and brittle. Skin scrapings taken by the vet should be able to tell if it is this.