When this outbreak happened at the barn I was boarding at neither of my horses got anything other than a little bit of a runny nose, and they were exposed to a gelding who had burst out in the pasture, the second to come down with it, nobody knew until it was too late, but only 4 horses got it, all under 5 years old, all vaccinated for it, and only the horse that I mentioned earlier came down with the ******* strangles.
I have also treated some nasty wounds, and the horses never became aggressive towards me or anyone else that needed to treat them. But I did not stay for hours every day constantly touching, rubbing, disinfecting, hosing, bandaging, etc. I made sure everything was quick and as painless as it could be. I think a lot would have to do with the horses personality and the how the owner was treating it.