In the U.S., the bovine tuberculosis (bTB) status of captive cervids has been monitored primarily through individual animal or whole herd TB skin testing, and by voluntary inspection at slaughter.
The 1999 Uniform Methods & Rules (UM&R) for Bovine Tuberculosis Eradication and 9 Code of Federal Regulations (CFR) Part 77 have detailed information on bTB testing in farmed/ captive cervids. Approved tests include the single cervical tuberculin test (SCT), the comparative cervical tuberculin test (CCT) and the Dual Path Platform VetTB Assay (DPP).
Skin Testing
The APHIS bTB regulations for farmed/captive cervids authorize the use of the single cervical tuberculin test (SCT) as a primary test, and comparative cervical tuberculin test (CCT) as a supplemental test as official tests for bTB in captive cervids. If an animal responds to the SCT then the animal can be retested with the CCT within 10 days or after 90 days.
Serological Testing
The Dual Path Platform VetTB Assay (DPP) is approved as both the primary test and subsequent secondary test for official program testing to diagnose bTB in farmed and captive elk, red deer, white-tailed deer, fallow deer, and reindeer when the test is conducted at the National Veterinary Services Laboratories (NVSL).
If the primary DPP test on an animal is positive, the animal is classified as a suspect and that animal or herd is quarantined by the state, and a secondary DPP test may be done after 30 days. If the secondary DPP is negative, the animal is then deemed negative and released. If the secondary DPP is once again positive, the animal is considered a ‘TB reactor’. According to regulations, TB reactors must be depopulated and submitted for a diagnostic necropsy. Lesions suggestive of TB, and specific lymph nodes are harvested and submitted to NVSL for analysis. Histopathology of the tissues is performed, and if positive, a polymerase chain reaction (PCR) test is then done. Tissues are submitted for culture whether the histopathology and PCR are negative or positive, and incubated for at least 60 days. If the culture is positive for TB, the animal is infected and further testing of the herd must be done. NVSL is now using a whole genome sequencing process and can identify if a particular TB organism is related to others in the library, and perhaps identify where it was transmitted from.