I wonder that there has not been any major outbreaks as dealers go from one breeder to another so they could have fish from 20 breeders . I visited the famous Korakuen garden in Okiama where they lost all the fish I was told that they would hunt for the best deal to replenish the few hundred koi they had but sometimes that can be dangerous . Myself I think it is best to stay with one or two breeders that breed their own
Regards
Eugene