Available as an MSU Extension Bulletin (Adobe Acrobat)

The CCT test is designed to determine if a response noted on the CFT test is more likely due to infection with Mycobacterium bovis or Mycobacterium avium. The CCT test can only be performed by a full-time State or Federal regulatory veterinarian. The test is performed by the interdermal injection of biologically balanced bovine PPD tuberculin and avian PPD tuberculin at separate cites in the cervical (neck) area. A determination as to the possible presence of bovine tuberculosis (Mycobacterium bovis) is made by comparing the responses of the two tuberculins 72 hours (+/- 6 hrs) following injection. Responses to the CCT test are plotted on the CCT scattergram. Classification of individual animals is made according to the zone that the animal is plotted on the scattergram. Cattle classified as reactors are subject to federal regulations overseeing reactor classification. Cattle classified as suspect on the CCT test must be retested after 60 days by the CCT test or shipped directly to slaughter under permit in accordance with State and Federal laws and regulations. If an animal is classified as a suspect on two successive CCT tests, they are subject to reclassification as a reactor. A response to the CFT test indicates that an animal has mounted an immune response capable of recognizing Mycobacterium bovis. This immune response may be caused by infection with Mycobacterium bovis. However exposure or infection with other closely related bacteria, most commonly Mycobacterium avium (avian tuberculosis) could also cause a CFT test response. By comparing the immune response to bovine and avian tuberculin using the CCT test, a more accurate assessment can be made as to the source of the immune response. The comparative nature of the test reduces the likelihood of a false positive test result for bovine tuberculosis.

Negative Animal
Any cattle, bison, or goats that are classified as negative after comparison of reactions to biologically balanced bovine PPD tuberculin and avian PPD tuberculin at separate cites in the cervical (neck) area. Classification is based on objectively measuring the swelling associated with each injection and plotting them on the official USDA CCT scattergram. If plotted in the negative zone, the animal is classified as bovine TB negative.

Reactor Animal
Any cattle, bison, or goats that are classified as reactor after comparison of reactions to biologically balanced bovine PPD tuberculin and avian PPD tuberculin at separate cites in the cervical (neck) area. Classification is based on objectively measuring the swelling associated with each injection and plotting them on the official USDA CCT scattergram. If plotted in the reactor zone, the animal is classified as a bovine TB reactor. Animals classified as a suspect on two sequential CCT tests 60 days apart are automatically reclassified as a reactor. Animals classified as reactors are subject to the rules and regulations governing this classification. Cattle classified as bovine TB reactors are quarantined to the premises where they are disclosed until a State or Federal movement permit can be obtained. The animals are submitted to appropriate diagnostic laboratories within 15 days for necropsy and further diagnostic testing.

Suspect Animal
Any cattle, bison, or goats that are classified as suspect after comparison of reactions to biologically balanced bovine PPD tuberculin and avian PPD tuberculin at separate cites in the cervical (neck) area. Classification is based on objectively measuring the swelling associated with each injection and plotting them on the official USDA CCT scattergram. If plotted in the suspect zone, the animal is classified as bovine TB suspect. Animals classified as bovine TB suspect by the CCT test can be retested by the CCT test 60 days after the first CCT Test injection or taken to submitted directly to an appropriate diagnostic lab for further testing. Animals classified as suspect on a second CCT test are automatically reclassified as reactors and subject to the rules and regulations governing this classification.