It is possible to eradicate bovine TB from cattle herds in Britain and Ireland, but to do so, “someone will have to throw big money at it,” Devon vet Dr Dick Sibley told a meeting of the Pedigree Cattle Trust (PCT) in Armagh last Thursday night.

It is the third time in recent years that Sibley has come to NI to speak to the PCT and during his latest trip he also put his views to Agriculture Minister Andrew Muir in a meeting facilitated by the Ulster Society for the Prevention of Cruelty to Animals (USPCA).

The message Sibley brings is challenging for all those involved in developing a TB eradication plan for NI. It is also attractive for those against a badger cull in NI as he believes the targeted removal of badgers in TB hotspot areas will ultimately have a limited impact.

His main argument is that the current TB skin test, which compares the reaction of the animal to two types of tuberculin (avian and bovine), leaves behind too many infected cows.

Some of these infected animals have a latent infection and don’t succumb to the disease. Others become infectious when exposed to a different disease challenge (such as BVD), a change in diet or hormonal changes post-calving. Finding these animals requires repeated testing using a variety of tests, suggested Sibley.

“Using the current skin test as we do, we have no hope of eradicating TB. No one has done it with the level of infection we have got. It is a screening test for infected herds, not a test for finding individual animals,” he said.

One option is to drop the avian injection site, meaning we just rely on what is currently the bottom lump. While it is a “very sensitive way of testing”, the problem is it would result in a significant number of “false positives”, so would come at a high cost for taxpayers and farmers, acknowledged Sibley.

The same applies for various alternative tests, such as the interferon gamma blood test, which will identify cows with TB that the skin test will miss, but costs around £30 per sample in lab fees.

Sibley has also been involved in trials of alternative tests that check for TB in dung, saliva or blood on Gatcombe Farm, a large dairy business in South Devon milking 340 cows through robots in a contained system.

History of TB

The farm has a long history of endemic TB, with 93 cows removed as TB reactors in sporadic outbreaks since 2012.

As part of the work at Gatcombe Farm, a total of 192 cows since 2015 have been identified as “high risk” given they had a bottom lump at a skin test. These animals have been repeatedly checked using these alternative tests. In total, 81% were shown to be infected with TB, although not all might actually be infectious, said Sibley.

He outlined how the farm has managed these high-risk cows separately, with no milk from these animals fed to calves and a recent decision to stop breeding replacements from the cows.

In 2019, the Gatcombe herd was declared TB-free and at that stage the use of the alternative TB tests was stopped. A TB breakdown occurred two years later.

Sibley questions Defra TB claims

Earlier in 2024, a paper was published in a scientific journal which highlighted that by the end of the fourth year of badger culling in parts of England, the Official TB Free status Withdrawn (OTFW) incidence was down by an average of 56%.

Dick Sibley believes the data is being manipulated to justify the badger cull in England.

He points out that OTFW is allocated to a herd when lesions are found in reactors at slaughter or when TB is cultured from a tissue sample. If there are no lesions nor a positive culture identified, a breakdown herd is instead classed as Official TB Free status Suspended (OTFS).

In his home area in the southwest of England (Devon, Cornwall and Dorset), the number of OTFW herds have been trending downwards, but OTFS herd numbers have generally been going in the opposite direction.

“These [OTFS] herds have got TB – you just have to look harder,” said Sibley. He suggested that part of the reason for TB reactors not having visible lesions at slaughter is because they are being picked up earlier by increased use of the interferon gamma blood test. “We are getting selective data here. If cattle have lesions, they are just a more advanced case,” said Sibley.

He believes that his questioning of the data is one of the reasons why his tenure on a Defra bovine TB partnership group was not renewed at the end of February 2024.

Bigger issues to confront than badgers

Earlier in his career, Devon vet Dick Sibley argued for the need to cull badgers to help control TB, but he now believes it is a pointless activity, with much bigger issues to be confronted, particularly around TB tests on farms.

“I have no special affinity to badgers. Our experience for over five years is that killing them is very hard work and expensive. Some farms have put in over £10,000 and they are niggled they still have TB,” he said.

He suggested there is still a lot more to be understood around how the disease is transmitted between cattle and that it is not just a respiratory spread, with faecal contamination of water or food also important. Given an adult dairy cow will produce 45kg of faeces daily compared to a badger at 100g, you have to kill a lot of badgers to equate to one infectious cow, argued Sibley.