The issues pertaining to the development of effective bTB vaccines – targeting both cattle and badgers, are extremely complex in nature.
They were discussed in detail at the recent North of Ireland Veterinary Association (NIVA) 2024 annual conference.
Dr. Sam Strain is chief executive for Animal Health and Welfare Northern Ireland (AHWNI). He explained that, where badgers are concerned, a form of BCG vaccine is at the centre of current discussion, adding:
“It can be used therapeutically. However, this is only the case when used in animals that have not been infected with TB.
“The reality is, that the population of badgers in Northern Ireland has an extraordinarily high level of TB within it. The immediate use of any type of vaccine on badgers will, in all probability, have very little effect.
“To make vaccination work within a badger population will first require a significant reduction in the levels of TB that already exist.”
Dr. Strain added that “the ultimate use of a vaccine on badgers is the direction of travel now being taken by most jurisdictions where TB is a major issue”.
Turning to the potential use of a vaccine within cattle populations, Dr. Strain indicated that the use of a BCG vaccine will lead to a cross reaction with the current skin test.
bTB vaccines
Dr. Strain continued: “Simply going in with a vaccine right now will generate lots of false positives when cattle are tested.
“Work already underway in England is looking at the development of a DIVA skin test for bTB. This comprises a cocktail of antigens that are specific to TB but not in the BCG.”
He added that he is “not party to all the results of this work up to this point. However, the test must overcome a number of hurdles.
“First of all, it must be effective in detecting TB infection in cattle, at least to the levels that can be obtained courtesy of the current skin test.
“DIVA must also deliver a very low number of false positives. It must be very specific.”
Prof. Philip Robinson, currently conducting research in veterinary public health at Harper and Keele Vet School, highlighted the need for agriculture to learn from the past in terms of how it dealt with bTB eradication today:
“We have already seen the quite extensive use of the BCG vaccine within badger populations in both Great Britain and the South of Ireland.
“But when it comes to the use of the vaccine in cattle, a degree of caution is required,” he said.
Prof. Robinson added that the science involved is “extremely complex and, in reality, it will take a number of years before all the issues involved are fully ironed out.”
“But what does concern me most, are the supply chain implications.”
“In reality, we would be putting an attenuated form of Mycobacterium bovis out into the supply chain.
“There may well be market and social acceptability issues coming into play if such a development was to be considered,” the professor outlined.
