I really hope it gets okay soon!
my friend had a jack russel, they lived on a farm, and they always played hide and seek in their huge barn. then one day the jack russell never wanted to go in there and they found it was because there was rat pee everywhere and rats were all about the barn. funny thing though, usually jack russells love anything 'rattish' and will hunt them out.
maybe something along those lines has happened with your dog
they got rid of the rats, and after about three months the dog went back in there as if nothing has happened.
do you have a cat??