ooh no. Poor pony! It swept through our barn about 7 years ago, and it was awful. It wasn't worth quarantining any one horse, because we figure someone had touched a horse with strangles and then came to visit horses at our barn.
Lots of compresses for their necks, and keep a close eye out for signs of strangles in any other horse at your barn.
I can't remember exactly, but I think we were treating horses at the barn for a few months... luckily my horse at the time didn't get it too badly.
I think it stays dormant for a while too? I have no idea how long, or I might be completely off base..?