Cattle vaccination can become an important item in the toolbox in the battle to eradicate bovine TB in herds, the UK’s chief vet has insisted.
Defra has announced that the first stage of field trials of the cattle Bacille Calmette-Guérin (BCG) vaccine and diagnostic test to differentiate infected from vaccinated animals (Diva) are under way in England.
Chief veterinary officer Christine Middlemiss said the trials on a cattle farm in Hertfordshire would test the specificity of the Diva test and gather safety data to check how it performs in the field. The test works by identifying proteins in infected cattle that are not present in uninfected animals.
A second phase of the trials, planned to start from February 2022, will combine the vaccine and diagnostic test in further herds across England and Wales.
It is hoped the trials will allow Defra to generate enough evidence to support a market authorisation application to the Veterinary Medicines Directorate to use both products in the UK, with the aim of rolling them out commercially by 2025.
Ms Middlemiss said experimental work at the Animal and Plant Health Agency laboratory at Weybridge had demonstrated full protective immunity for about one-third of cattle given the BCG vaccine, some immunity in a further third, but no response in the final third.
“Vaccination won’t be the whole story of our controls, just as we see in our response to coronavirus,” Ms Middlemiss said. “But absolutely, being able to protect animals that are free of the bacteria – over 60% of them to some degree – is worth having.”
Ms Middlemiss also noted that a field trial in New Zealand from 2014 to 2018, of cattle given a lower dose of the BCG vaccine, provided more than 85% protection.
Asked whether a TB cattle vaccine and Diva test would be commercially available for farmers to use from 2025, she said: “I think it really is pretty viable and that’s because we have now got the Diva test and that’s the key difference.”
Defra is carrying out cost-benefit studies to understand where it will prioritise the use of the vaccine and how much it will cost.
Ms Middlemiss said it would be “fairly expensive” to vaccinate cattle, but she anticipates that the cost of the Diva test will be similar to the current tuberculin skin test. No decision has been made on who will pay for it.
The World Organisation for Animal Health has been made aware of the trials and Ms Middlemiss said it was “really important” that the organisation validated the Diva test to allow trade in cattle vaccinated against bovine TB.
NFU deputy president Stuart Roberts said: “This latest development will take time, and we hope that vaccination of cattle will further contribute to eliminating this disease when it is available.
“However, we must continue to remove the risk from all vectors to achieve eradication, and we remain significantly concerned about the direction of travel from the UK government in its bovine TB eradication strategy.”
James Russell, president of the British Veterinary Association, added: “The launch of these field trials marks the culmination of years of ground-breaking research and efforts by the veterinary scientific community to expand the range of tools available to vets and farmers to tackle bovine tuberculosis.
“We look forward to seeing the results of the trials on the vaccine and test’s accuracy and safety.”