Live Animal Testing
Diagnosis of TB in Live Animals:
Testing Flow Chart, June 2008 (PDF 34 KB)The first test to detect possible carriers of bovine tuberculosis is the Caudal Fold Test (CFT), in which a small amount of purified protein derivative (PPD) is injected into the fold of skin at the base of the tail.
- The CFT is read 72 +/– 6 hours later.
- If the test is negative, no further action is required.
- If the test is positive, the animal is classified as a responder and requires further testing.
- It is normal to have a false positive rate of 1–2% during a whole herd test.
Responders must receive a Comparative Cervical Test (CCT) within 10 days of the CFT. If this time–window is missed, the animal must be tested after 60 days have elapsed.
- The CCT consists of two injections given in the skin of the neck – one of bovine tuberculin extract and one of avian tuberculin extract.
- The CCT is read 72 hours later.
- The response is plotted on a special graph – a scattergram.
- The scattergram allows an animal to be classified as negative, suspect or reactor.
- CCT negative – no further action.
- CCT suspect –either humanely destroyed, necropsied and samples tested at a diagnostic laboratory, OR remain in the herd under quarantine and have a second CCT after 60 days. If the second test is still positive, the animal will be humanely destroyed, necropsied and tested.
- CCT reactor – humanely destroyed, necropsied and samples tested at a diagnostic laboratory.
Necropsy and laboratory testing:
- Animal necropsy and laboratory testing of the samples obtained (including microbiology, molecular biology and histopathology) are needed to definitely diagnose bovine TB. The samples that are required to be collected are the lymph nodes of the head, thorax and abdomen; however, any other abnormalities that are found should be sampled.
- These tests may take several weeks or months to complete.
- If the necropsy and sample testing indicate the animal is not infected with TB, the whole herd must be evaluated and may be tested a minimum of 60 days after removal of the reactor.
- If the necropsy and sample testing indicate the animal is infected with bovine TB, the whole herd is quarantined.
Herds containing infected animals are quarantined and the herd declared affected.
- The owner/producer, along with the government agencies involved, can apply for either whole herd depopulation OR develop a whole herd test and removal plan.
Caudal Fold Injection
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Caudal Fold Response
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Caliper Measuring
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CCT Injection
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CCT Response
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Contact us for more information:
California Department of Food and Agriculture
Animal Health and Food Safety Services, Animal Health Branch
1220 N Street, Room A-107
Sacramento, California 95814
Telephone: (916) 654-1447
Fax: (916) 653-2215
or send an email to: ahbfeedback@cdfa.ca.gov