PI animals are highly infectious and should be culled or slaughtered as soon as they are identified. If you decide to retest the PI animal, it should be isolated from the rest of the herd as soon as it is identified.
PI animals should not be traded. Members of BVDFree agree not to move Persistently Infected (PI) animals other than directly to slaughter (or through a dedicated red slaughter market). Knowingly selling an infected animal may also be in breach of the Sale of Goods Act.
BVD causes significant losses in herds that have it, through acute (transient) as well as persistent infection. An animal that is transiently infected will suffer lower immunity and increased susceptibility to other diseases as a result. The daily additional hidden costs of keeping a PI in the herd far outweigh any value of keeping the animal.