Pre-movement TB testing: What is the expert view?

Pre-movement testing for TB – a controversial topic at present – could be useful in a very targeted way, focusing on high-risk herds, according to a veterinary expert.

Prof. Simon More, of the UCD Centre for Veterinary Epidemiology and Risk Analysis (UCD CVERA), was speaking on the topic of TB eradication before the Oireachtas Joint Committee on Agriculture, Food and the Marine.

Responding to a question from Fianna Fail agriculture spokesperson Charlie McConalogue on whether pre-movement testing for TB would make much of an impact in eradication efforts from a scientific basis, the professor was of two minds.

“In terms of pre-movement testing, we did a study, about 12 years ago where we specifically investigated whether pre-movement testing would be useful here,” he said.

“What we did was a little bit like a cost-benefit because there’s a lot of effort involved in pre-movement testing and would that help in terms of picking up more breakdowns.

Our view at the time was that pre-movement testing would only be useful in a very targeted way, essentially focusing on high-risk herds.

However, the professor made two broader points on the matter.

“In terms of first principles of course if this is a high-risk herd and you’re having animals moving out of that herd, if those animals are tested at appropriate times – and six months is probably appropriate because it takes time for the infection to develop and to also test positive to the test – it could be useful.”

Prof. More also highlighted, considering the animal-based decisions made in differentiating between clear and infected herds, his worries: “I would have concerns that with our tests, we’re really stretching the ability of the tests to do that.”

Continuing, he explained that the pitfall with pre-movement testing is the focus on individual animals as opposed to the broader herds.

“If you were to move to a risk-based situation, it is much safer to work at a herd level – so we’re saying that all of the animals in the herd are of equivalent herd status; whereas pre-movement testing is moving from that to actually looking at the individual animal.

We know, say an animal’s infected, the probability with the skin test we’re going to pick up infection on average is 50%; but it will be much generally higher if it’s later in the course; it would be much less if it’s earlier in the course.

“I guess the fundamental question is are we doing enough. That’s really where I’m coming from.”

Asked if TB eradication can be completed without introducing risk-based movement, Prof. More was not optimistic.

“To be honest I cannot see us – based on all of the evidence I have in front of me, I’d have real concerns about whether we can eradicate – certainly within a reasonable time – without a really robust risk-based system which probably would need to include trading, unless we get a better test etc.”