Question to the Department for Environment, Food and Rural Affairs:

To ask the Secretary of State for Environment, Food and Rural Affairs, if he will publish the number of (a) negative or (b) inconclusive Bovine Tuberculosis first culture tests on pigs that have subsequently returned a positive test result on the second culture in each of the last three years.

Bovine tuberculosis (TB) is a chronic, infectious and primarily respiratory disease caused by the slow-growing bacterium Mycobacterium bovis (M. bovis). It is mainly a disease of cattle and other bovines, but it can affect a wide range of mammal species, including pigs.

TB is a notifiable disease in pigs and other non-bovine farmed animals. This means that suspected lesions of TB detected in the carcases of those animals during veterinary post-mortem examination or routine post-mortem meat inspection in the slaughterhouse must be reported to the Animal and Plant Health Agency (APHA) without delay. APHA will place the affected herd under precautionary movement restrictions pending completion of bacteriological culture and whole-genome sequencing to try to identify the bovine TB bacterium from those lesions in the laboratory.

On certain occasions it becomes necessary to repeat an initial negative culture and, because M. bovis is a slow-growing bacterium, this will substantially increase the turnaround time for the final laboratory results.

The numbers of primary cultures and re-cultures are shown in the table below, along with the results thereof.

The higher percentage of re-cultures in 2020 and 2021 are due in part to a decision that all pig samples sent from the bovine TB Low Risk Area of England and all of Scotland should be subject to primary culture and secondary culture, conducted simultaneously (in parallel) in order to minimise the time the affected herd is under precautionary movement restrictions. The large number of ‘other’ results in 2021 is due to a large proportion of cultures that had not yet completed the full incubation time at the time the data were extracted.

APHA has validated a new polymerase chain reaction (PCR) test that can detect the bovine TB bacterium directly from tissue samples collected at post-mortem meat inspection, without the need for bacteriological culture. The major advantage of this new method is that it will typically take only three weeks to report a result from the day the sample reaches the laboratory, compared with 6-22 weeks for bacteriological culture. It is hoped that this new PCR test for TB will enter routine use at APHA for tissue samples from pigs and other non-bovine animals early in 2022.