Coon,
I've come to the conclusion that what Seth saw at my place was either a mangy coyote or coyote/dog cross. I've also came to the conclusion that the reason that it showed no fear and walked right past him was that it was so sick that it didn't have enough strength or will to be afraid. Another possibility was that it was a wild, or abandoned, dog. People will take sick/mangy dogs out and drop them off rather than deal with the problem.
Speaking of sarcoptic/red mange, if I had that dog, the picture of which you posted, and wanted to save it, I would do this:
1. Immediately rub it down with a mixture of used oil and diesel--the entire body.
2. Give it an injection of ivomec.
3. Put it on a high/high protein diet.
In most cases, the rub with oil/diesel will immediately knock the mange back.
In most cases, the ivomec will work on the sarcoptic mite--an external parasite.
In most cases, the high protein diet will cause the animal to secrete increased amounts of skin oil.
The increase in skin oil, which is secreted into the hair folicle, will work on the mite--which burrows into the hair folicle. The reason that sarcoptic mange can not be easily treated is that the mite is not on the surface of the skin but in the folicle. (A very good veteranarian in Ada, Oklahoma, back in the 1970's, said to me, "We've had some success with it [red mange] by treating the skin and by increasing the protein level in the diet. I don't know why that works." Since I knew that throwing cotten seed cake to an old mare would increase her skin oil to the point that she, from a distance, looked wet, I immediately knew why it worked.) Protein does wonders for most animals.
The treatment must continue over a period of time. One rub with oil and diesel and one can of dog food isn't going to do it.
Regular skin care and good diet will go a long ways toward eliminating skin problems on dogs--and probably people.
A couple of other things: Ivomec applied to the skin is a good route to go. Just remember that that medicine is absorbed through the skin--the dog's skin and your skin--and can be overdosed. Avon Skin-so-Soft also helps.
BUT, it remains true that a sarcoptic dog, and his owner, are often better off if the animal is humanely put down. And they should not be bred. One reason for that is that some lines of dogs appear to be more susceptible to the skin problem. The sarcoptic mite can often be found on dogs that have no other sign of the disease. They may have a genetic resistance to it--or they may be being fed and cared for properly.