Section 77.34 - Official tuberculosis tests(a)Primary tests -(1)Single cervical tuberculin (SCT) test.(i) The SCT test is a primary test that may be used in individual captive cervids and in herds of unknown tuberculous status. Each captive cervid that responds to the SCT test must be classified as a suspect until it is retested with the CCT test and is either found negative for tuberculosis or is classified as a reactor, unless, with exception of a designated accredited veterinarian, the testing veterinarian determines that the captive cervid should be classified as a reactor based on its response to the SCT test. A designated accredited veterinarian must classify a responding captive cervid as a suspect, unless APHIS determines, based on epidemiological evidence, that the captive cervid should be classified as a reactor. A captive cervid that responds to the SCT test must not be retested using the DPP® test.(ii) The SCT test is a primary test that may be used in affected herds and in herds that have received captive cervids from an affected herd. When used with affected herds or in herds that have received a captive cervid from an affected herd, the SCT test may only be administered by a veterinarian employed by the State in which the test is administered or employed by USDA. In affected herds or herds that have received captive cervids from an affected herd, each captive cervid that responds to the SCT test must be classified as a reactor, unless APHIS determines, based on epidemiological evidence, that the cervid should be classified as a suspect because of possible exposure to a tuberculous animal.(2)DPP® test.(i) The DPP® test is a primary test that may be used in individual captive elk, red deer, white-tailed deer, fallow deer, and reindeer, and in herds of these species that are of unknown tuberculous status. Except as specified in paragraph (a)(2)(ii) of this section, each captive cervid that has non-negative test results to this initial DPP® test will be classified as a suspect and retested with the DPP® test. A captive cervid that has non-negative test results to the DPP® test must not be retested using the SCT or CCT test.(ii) The DPP® test is a primary test that may be used in affected herds of captive elk, red deer, white-tailed deer, fallow deer, and reindeer, and in herds of these species that have received captive cervids from an affected herd. In such herds, each captive cervid that has non-negative test results to the DPP® test will be classified as a reactor, unless APHIS determines that the captive cervid should be classified as a suspect because of possible exposure to a tuberculous animal.(b)Supplemental tests -(1)Comparative cervical tuberculin (CCT) test.(i) The CCT test is a supplemental test that may only be used in order to retest captive cervids that have been classified as suspects after being tested with the SCT test. The CCT test may be used in affected herds only after the herd has tested negative to at least two whole herd SCT tests and only with the prior written consent of APHIS. The CCT test may not be used as a primary test.(ii) A captive cervid tested with the CCT test must be classified as negative if it has a response to the bovine PPD tuberculin that is less than 1 mm.(iii) Unless the testing veterinarian determines that the captive cervid should be classified as a reactor because of possible exposure to a tuberculous animal, a captive cervid tested with the CCT test must be classified as a suspect if:(A) It has a response to the bovine PPD tuberculin that is greater than 2 mm and that is equal to the response to the avian PPD tuberculin; or(B) It has a response to the bovine PPD tuberculin that is equal to or greater than 1 mm and equal to or less than 2 mm and that is equal to or greater than the response to the avian PPD tuberculin.(iv) A captive cervid tested with the CCT test must be classified as a reactor if: (A) It has a response to the bovine PPD tuberculin that is greater than 2 mm and that is at least 0.5 mm greater than the response to the avian PPD tuberculin; or(B) It has been classified as a suspect on two successive CCT tests.(C) Any exceptions to the reactor classification under the conditions in paragraph (b)(1)(iv) of this section must be justified by the testing veterinarian in writing and have the concurrence of APHIS.(2)DPP® test. The DPP® test may be used as a supplemental test in order to retest captive cervids that have been classified as suspects based on an initial DPP® test. In such instances, the supplemental DPP® test must evaluate a new serum sample drawn from the cervid no sooner than 30 days after the initial DPP® test. A captive cervid that has non-negative test results on two successive DPP® tests will be classified as a reactor, unless APHIS determines that another disease classification is warranted. 78 FR 1722 , Jan. 9, 2013, as amended at 79 FR 43926 , July 29, 2014