Demodetic mange?

Question
Hi. I have been raising Boxers for a really long time. I'm huge on health, and have all of my dogs health tested before breeding (OFA, heart, ect.). I had bought a brindle female last year, she's 8 months old now. I looked over a year for her, wanting the right dog from the right breeder. I had her ears cropped, and told the vet to not use ACE. We went to pick her up after the ear crop. She was ice cold, and wobbly. Half way home, we live an hour away from the vet, she had a seizure. We called the vet back, but he was already out. We got her home, and finally got hold of him. He said she would be fine, don't worry. And it turned out he DID use ACE on her. Shortly after, she came up with a spot of fur missing off the top of her head. Took her back to the vet and he said it was demodectic mange, and that she shouldn't be bred. He did a skin scrapping, and found one adult mite, and that's it. A few days after that, she got into a hornet's nest, and was stung 5-6 times on her back. She did lose hair in those spots where she was stung. Another skin scrapping, and no mites were found. The spot on her head did not look like 'red' mange. This vet is still swearing that that's what it was, and if I choose to breed her anyway, he will make sure to tell any potiental puppy buyers about it. I had no plans on breeding her until I figured this mess out anyway, as I don't want to produce puppies with this same problem (I know it's an immunity problem). Another vet did a skin scrape, and found no mites, and thinks that it was  a fluke, especially because of the way the ear crop went. I have never dealt with this in 15 years of breeding, and was hoping that you could give me your thoughts. The spot cleared itself up within a few weeks, and no other outbreaks. If this was your dog, what would you do? I'm at a loss here, and am not sure. She's a beautiful dog, with a wonderful pedigree, and comes from health tested parents. I would really like to add her to my breeding program, as I think she has a lot to offer. But, I don't want to produce puppies with this problem. Any thoughts that you may have would be greatly appreciated. Sorry this was so long.

Answer
Hi Rita,

Localized demodectic mange is extremely common in puppies, who have an immature immune system to start and then are rapidly subjected to multiple stressors; worming, vaccination, weaning, leaving the litter/going to new homes.  Stress has a short-term depressive effect on the immune system, which can allow the mites to 'gain the upper hand', as it were, and then spots of mange may develop.  Your girl had the added stresses of an ear crop and a bad reaction to the surgical drugs, so it's not at all surprising she might have had a spot of mange.  

In dogs with inherited immune dysfunction, localized mange if left untreated will progress to generalized mange (covering most of the body) - it is these dogs who should not be bred.  A puppy with localized mange that resolves without treatment is a prime breeding candidate because you know at that point the immune system is functioning properly.

Further, all dogs have these mites on their bodies; one adult mite in one skin scraping is hardly an out of control infestation.  Of course I've no way of knowing whether this was truly mange or not, but with just one mite found it could have been any number of other things, as well.

There's a bit more on demodectic mange here (maybe pass this on to that first vet!):
http://www.marvistavet.com/html/demodectic_mange.html

As for what I would do:  If I had a quality, typey, health-tested bitch from health-tested parents who'd had a spot of demodex as a puppy that self-resolved and never recurred, I wouldn't hesitate to breed her. :)

Best of luck to you!