Knowing that my pups are going to have to work around sheep and cattle, I always like to get them around them as soon as possible, so they grow up familiar with them. But also the farm know me so know I'd never allow my dogs to cause any damage to their livestock.
Also, I'm very old!! Had my first dog in 1955, before vaccinations were around. My friend said to me one day, "You are old, you must have seen loads of distemper, what are the signs?" I had to tell her that I'd only ever seen one case, a dog down the other end of the road when I was about 10 years old. Contrary to what people think, in those days Distemper was very rare and dogs were not dying on the streets.
Of course, all this was many years before the first cases of Parvo Virus, which started around 1973. At that time I was instructing at a dog club, and one of our members was one of the very first cases. She bred a litter of GSD's which contracted Parvo. The pups were taken to the vet college in Edinburgh, which at that time was the place doing the research on it. It was there that they found that the cat flu vaccine helped, but it was too late for Marion's pups, all but one died from the parvo, and the one who survived that was so brain damaged that the vets put it to sleep. Trouble was, being a completely new illness dogs had no natural immunity to it and at that time, to contract it really was a death sentence! We really did wonder if it could spell the end of dogs! But of course that was not the case. The next generation of dogs started to acquire a certain amount of natural immunity, and a vaccines were developed, and the risk was greatly reduced. But I'm now hearing that there is a new strain doing the rounds causing problems. But I'm sure the research labs will soon get a handle on that too.