Common misconceptions about Bovine Tuberculosis (TB)

This page provide useful advice and guidance on common misconceptions about Bovine Tuberculosis.

The post mortem is more reliable than the TB skin test

There are frequent misconceptions surrounding the post mortem check on TB reactors. The post mortem is primarily a public health check. It is carried out while the carcase and organs travel past the inspector on an automated line. It is quite cursory in respect of some tissues which are not normally harvested for human consumption, e.g. the lungs. Farmers may think that the post mortem is more reliable than the skin test, whereas the opposite is the case.

If a skin reactor is post mortem negative it does not have TB

It is a misconception that if a skin reactor is post mortem negative, that the reactor does not have TB and no further herd testing should be required. That is not the case - the skin test is more reliable at finding positive animals than post mortem. A skin reactor is highly indicative of disease and therefore at least one herd test will be required.

Lateral Check Tests are only carried out where nose to nose contact has been possible

Lateral Check Tests are carried out to control the risk from an infected herd. Some herd owners may think that we only consider testing herds where nose to nose contact has been possible, but spread of infection via wildlife must also be considered. If wildlife is carrying infection, boundaries such as roads, streams, boggy areas or double fencing may be irrelevant. Where animals have grazed over the last year or more may also be considered.

After a TB breakdown Annual Herd Tests will revert to the month they used to take place

There is an idea that if a herd has usually done an Annual Herd Test (AHT) in a particular month for many years, then the herd owner is entitled to expect his AHT to revert to that date after any TB breakdown, or cycle of Lateral Check Tests, or after they have gone out of stock for a while. This is not the case. Why? DAERA pay for TB testing and must make sure that tests are not done unnecessarily. Herd tests are done at least once per year and this means setting the next herd test with a due date a year from the last test, which may have been done outside the usual time, e.g. a Lateral Check Test. Herd owners should also be aware that a Check Herd Test (CHT) is carried out about 6 months after a herd breakdown is resolved.

A badger cull will stop TB

There is a perception that if a badger cull is carried out locally or throughout NI, that all TB problems will disappear. This is unlikely to be the case as TB is a multifactorial disease with several different methods of spread.

A negative TB skin test means that an animal is definitely free of disease

An animal that has a negative TB skin test will usually be free of the disease, however this is not guaranteed. The TB skin test is not perfect and it is important to look at the TB history of the animal and the herd also. The more years the herd has been free of TB, the more confident you can be that any animals originating from that herd will be TB free. Likewise, an animal that has had no bovine rises (“bottom lumps”) in its test history and has never been an inconclusive animal, is more likely to be TB free.

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