You can contain strangles by using clorox to clean water troughts, feed bowls, etc. If they are over it, they shouldn't pass it on to another horse or contaminate their pasture - however, thirty days quarantine is NEVER a bad thing. Just fence them off from the othr horses, and don't use a community water tank, buckets, etc.
Will it hurt to soak the trailer with clorox before I move them? We were just going to take it to the power washer but it should air out fast.