9 C.F.R. § 77.4
(a) A State animal health official may request at any time that the Administrator designate part of a State as having a different tuberculosis classification under this part than the rest of the State. The requested zones must be delineated by the State animal health authorities, subject to approval by the Administrator. The request from the State must demonstrate that the State complies with the following requirements:
(b) Retention of APHIS recognition of a zone is subject to annual review by the Administrator. To retain recognition of a zone, a State must continue to comply with the requirements of paragraphs (a)(1), (a)(2), and (a)(3) of this section, as well as the requirements for maintaining or improving the tuberculosis risk classification of each zone in the State, and must retain for at least 2 years all certificates required under this part for the movement of cattle, bison, and captive cervids.
(Approved by the Office of Management and Budget under control number 0579-0146)