Iowa Code § 165.32: Retest.

The secretary of agriculture may order a retest of any dairy or breeding cattle at any time when, in the secretary’s opinion, it is necessary to do so, and shall, once in three years, order the tuberculin testing of any cattle to conform to and comply with the regulations of the federal bureau of animal industry in any county where the percentage of bovine tuberculosis has been reduced to one-half of one percent or less, subject to the provisions of this chapter with reference to the disposition or slaughtering of animals found to be reactors when given a tuberculin test. Such county shall be a modified accredited county, and it shall be unlawful for any person to transport any dairy or breeding cattle into such county unless they have been examined for tuberculosis as provided in this chapter.