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The testing information summarized here describes the typical approach for bovine TB during a disease investigation. However, the actual live animal testing for an individual herd will factor in considerations such as herd size, epidemiological data and the capacity to deliver different testing methods.
Testing for bovine TB during an investigation involves both live animal and laboratory testing. The full testing process can take up to 14 weeks as the final confirmatory test (laboratory culture) can take up to 12 weeks to complete.
There may be some situations where a second herd test is required to increase the confidence that a herd is not infected. The risk factors that would require a second test would be known before testing starts and will be explained to the producer. The second test would normally be done 6 to 12 months after the first test.
Risk assessments for herds with negative histopathology results will determine if a herd may be eligible for release from quarantine before final laboratory culture results are received.
The Compensation for Destroyed Animals and Things Regulations provide for compensation for animals sent for postmortem testing or destroyed for disease eradication.
Lifeline herds
When an infected animal is identified at slaughter, its whole life is traced back to the birth herd and every herd in which this animal resided/was part of during its life, is identified as a "lifeline herd". There may be limited investigative actions on premises that are not believed to be infectious and contaminated by an infected animal, for instance a premises where the animal spent less than 48 hours.
Lifeline herd testing
Primary live animal test
- Caudal Fold Tuberculin (CFT)
Ancillary live animal test(s)
- Parallel ancillary tests (blood samples during the CFT testing process)
- Gamma interferon (IFN -g) assay [BOVIGAMTM] when operationally feasible (may be limited to specific sub-groups in a herd)
Postmortem testing
- All reactor animals from the primary test and/or ancillary testing go through postmortem inspection with tissue samples collected for confirmatory testing
Confirmatory testing
- Histopathology and culture testing is required for all reactors
- A Polymerase Chain Reaction (PCR) test may also be completed on tissues where histopathology indicates the presence of mycobacteria
- A positive PCR or laboratory culture result is a confirmed case
Infected herds
A herd will be declared infected if:
- an infected animal is definitely traced to a herd from where it was moved from a short period before being found to be infected at slaughter or
- herd testing (from any category) in support of a bovine TB investigation detects an infected animal
An infected herd is tested to better understand the prevalence of the disease within the herd and to identify animals where tissue samples will be required even if there are no signs of bovine TB. Testing also informs disease investigation measures of other epidemiologically linked herds.
Infected herd testing
Primary live animal test
- CFT
Ancillary live animal test(s)
- No additional live animal tests are completed
Postmortem testing
- All reactor animals go through postmortem inspection with tissue samples collected for confirmatory testing
- All other animals go through postmortem inspection with tissue samples collected from any animals with signs consistent with bovine TB for confirmatory testing
Confirmatory testing
- Histopathology and culture testing is required for all reactors and any animals found with lesions consistent with bovine TB when slaughtered
- A PCR test may also be completed on tissues where histopathology indicates the presence of mycobacteria
- A positive PCR or laboratory culture result is a confirmed case.
Contact herds
Contact herds are all herds that shared a fence line or may have co-mingled with the infected herd. Each contact herd is evaluated and assigned a disease exposure risk categorization.
High risk contact herds
A herd where there has been repeated close direct contact events with an infected herd over the critical period which equates to significant opportunities for bovine TB transmission between herds.
For example:
- commingling with an infected herd for sustained periods during summer (such as intentional shared summer pasture)
- commingling with an infected herd for any period of time during fall/winter/spring period (such as shared winter-feeding areas)
High risk contact herd testing
Primary live animal test
- CFT
Ancillary live animal test(s)
- Parallel ancillary tests (blood samples collected at the time of reading for the CFT test)
- Gamma interferon (IFN -g) assay [BOVIGAMTM] when operationally feasible (may be limited to specific sub-groups in a herd)
Postmortem testing
- All reactor animals on CFT and/or gamma interferon go through postmortem inspection with tissue samples collected for confirmatory testing.
Confirmatory testing
- Histopathology and culture testing is required for all reactors
- A PCR test may also be completed on tissues where histopathology indicates the presence of mycobacteria
- A positive PCR or laboratory culture result is a confirmed case
Moderate risk contact herds
Where there is a history of moderate direct or indirect contact events with an infected herd for example:
- fence-line contact with an infected herd during the fall/winter/spring period only
- commingling with an infected herd sporadically or for short periods during summer period (for example, broken fences)
- exposure to equipment that was shared with an infected herd without thorough cleaning before/after use (for example feeding or watering equipment)
- access to a water source that has been shared with an infected herd
Moderate risk contact herd testing
Primary live animal test
- CFT
Ancillary live animal test(s)
- Gamma interferon (IFN -g) assay [BOVIGAMTM] when operationally feasible (may be limited to specific sub-groups in a herd)
Postmortem testing
- All reactor animals on CFT and/or gamma interferon go through postmortem inspection with tissue samples collected for confirmatory testing
Confirmatory testing
- Histopathology and culture testing is required for all reactors
- A PCR test may also be completed on tissues where histopathology indicates the presence of mycobacteria
- A positive PCR or laboratory culture result is a confirmed case
Low risk contact herds
A herd with a history of low level direct or indirect contact events with an infected herd
For example:
- fence-line contact during summer pasture period only
- short duration contact with an infected herd
Low risk contact herd testing
Primary live animal test
- CFT
Ancillary live animal test(s)
- Serial ancillary tests for CFT reactor animals (completed after CFT)
- Comparative cervical tuberculin (CCT) test or Gamma interferon (IFN -g) assay [BOVIGAMTM]
Postmortem testing
- All reactor animals from the ancillary test go through postmortem inspection with tissue samples collected for confirmatory testing
Confirmatory testing
- Histopathology and culture testing is required for all reactors
- A PCR test may also be completed on tissues where histopathology indicates the presence of mycobacteria
- A positive PCR or laboratory culture result is a confirmed case
Trace out herds
All trace out herds are high risk because of their potential to spread disease.
Trace-out herds received animals from an infected herd and are therefore the highest risk for exposure to disease. All eligible animals (6 months of age or older) in the herd are tested.
Any trace-out animals that are found in the herd are destroyed with confirmatory tissue testing regardless of their test results.
The same testing approach is used for
- a breeding herd where a trace out animal is located
- a breeding herd where a trace out animal has transited through the herd
- a breeding herd where the trace out animal died while in the herd, or transited through the breeding herd, and cannot be located on another premises, both resulting in the trace-out animal being unavailable for confirmatory tissue testing
Where a trace-out animal has been confirmed to have entered a breeding herd, and no evidence is available to demonstrate that it has left the herd, but the animal cannot be identified for confirmatory tissue testing, a second herd test may be performed 6 to 12 months after the first herd test.
Trace out herd testing
Primary live animal test
- CFT
Ancillary live animal test(s)
- Parallel ancillary tests (blood samples collected at the time of reading for the CFT test)
- Gamma interferon (IFN -g) assay [BOVIGAMTM] when operationally feasible (may be limited to specific sub-groups in a herd)
Postmortem testing
- All reactor animals go through postmortem inspection with tissue samples collected for confirmatory testing
- All trace-out animals are destroyed with confirmatory tissue testing regardless of their live animal test results
Confirmatory testing
- Histopathology and culture testing is required for all reactors
- A PCR test may also be completed on tissues where histopathology indicates the presence of mycobacteria
- A positive PCR or laboratory culture result is a confirmed case
Trace-out animals in feedlots
Where a trace-out animal is currently located in a terminal feedlot operation the approach involves arranging for destruction and disposal by way of slaughter in an abattoir under federal or provincial inspection.
For non-terminal feedlots, the approach will depend on whether the trace-out animal has had direct or indirect contact with animals potentially destined for a breeding herd.
Trace in herds
Trace in herds are herds that provided animals/sold animals to the infected herd.
Trace in herd testing
Primary live animal test
- CFT
Ancillary live animal test(s)
- Available serial ancillary tests for the testing of reactor animals
- Comparative cervical tuberculin (CCT) test or
- Gamma-interferon (IFN-ɣ) assay [BOVIGAMTM]
Postmortem testing
- All ancillary test reactor animals go through postmortem inspection with tissue samples collected for confirmatory testing
Confirmatory testing
- Histopathology and culture testing is required for all reactors
- A PCR test may also be completed on tissues where histopathology indicates the presence of mycobacteria
- A positive PCR or laboratory culture result is a confirmed case
Other testing
Proximity testing of herds of susceptible livestock located in a 5 km area from the boundary of each infected premises. Testing methods will be determined by the species involved and a risk evaluation.