9 C.F.R. § 73.1b
Under the Animal Health Protection Act (7 U.S.C. 8301 et seq.), the Secretary may promulgate regulations and may prohibit or restrict the movement in interstate commerce of any animal, article, or means of conveyance as the Secretary determines necessary to prevent the introduction or dissemination of any pest or disease of livestock. Pursuant to this authority, the Department has quarantined various areas because of cattle scabies and has issued the regulations in this part governing the interstate movement of cattle from such areas. It is the policy of the Department to quarantine those portions of any State that are clearly identifiable, and in which exist animals affected with cattle scabies, or mites which are the contagion of said disease and not to quarantine an entire State for cattle scabies if the State adopts and enforces requirements for the intrastate movement of cattle that are at least as stringent as the requirements in the regulations in this part for interstate movements of cattle. Further, it is the policy of the Department to remove the quarantine from any quarantined area when it is determined that scabies-affected animals and the mites which are the contagion of scabies no longer exist in such areas.
9 C.F.R. §73.1b