Hi, foxes used to carry distemper I believe , but I dont think they do any more. My main worry of dogs being around where foxes have been is the chance of the dog catching sarcoptic mange - sometmes called fox or red mange. Keep an eye out for little pink or scabby patches on the front of their arm pits , chest or on the top of their head, which is where puppies usually show it first. It you suspect he may have these, dose him with Stronghold drop on - from the vet straight away, dont wait for a diagnosis. Having had this problem myself in the past, all my puppies are protected with Stronghold from 6 weeks to 12 months, as often puppies will contract it where an adult will not. It also clear fleas and treats for roundworm, so if you do use it dont worm with anything else until he's the age where he may need a tapeworm treatment. But I dont mean to frighten you, its just that I have had a bad experience with fox mange , its very unlikely that your puppy will catch anything. Try not to worry too much - enjoy him!!