TB control strategy should centre on complete herd health history

AFTER LOSING 60 pedigree Holsteins to bovine TB, one Cheshire producer and his vet believe the disease should be tackled in a more radical way.

Alhough his herd is now clear, the producer concerned – who runs 400 milkers – prefers not to be named. But he and Neil Howie, senior farm partner in the Nantwich Vet Group, believe the way he handled the major TB breakdown has lessons for others.

“The first is it is possible to buy in TB, no matter how carefully cattle are sourced. We had never seen TB until two years ago, when we restocked after a foot-and-mouth contiguous cull. We only bought from herds that had tested clear, but we had 20 reactors at our first test,” recalls the producer.

Having again been made aware that the herd screening tuberculin skin test could miss individual infected animals, the producer persuaded DEFRA vets to cull some animals that tested negative as direct contacts.

“When you work with cows you know when there is something wrong with them. It may be an unexplained fall in yield, a change in behaviour or lethargy. We sent 10 non-reactors, two had TB and one of these had lesions.

“The DEFRA vet was excellent and could not have done more within the present control framework. I am sure what we did helped us clear the problem more quickly. The industry urgently needs a more accurate TB test, but in future we will pay to skin test any purchased cattle.”

Should there be another breakdown, he plans to use gamma interferon blood testing at his own expense. And, so better precautions can be taken, he believes DEFRA should inform producers about TB incidents. He was not told when a neighbouring unit was put under restrictions.

The rapid spread of bovine TB means he and other cattle producers could face mandatory pre-movement testing of store and breeding stock in the near future.

But Mr Howie describes this idea as perverse, because it will seriously disrupt farming and is unlikely to be effective. “DEFRA are the servants of society and producers, so they should listen more to those who are telling them they must respect the way the farming industry operates,” he claims.

“The concept of restricting movements until a test is done flies in the face of the industry’s history, would be a logistical nightmare and would fail to get producers’ co-operation.”

However, he accepts that cattle trading, rather than wildlife movement, is responsible for long distance spread. His answer is for DEFRA to help buyers by being more open with information about infected herds.

Instead of just acknowledging whether or not TB is present in a parish, Mr Howie would like buyers, or their vets, to be able to check the past TB status of a farm from which cattle are being sourced.

He believes producers have to accept responsibility for trying to keep out TB. However, he concedes that the tuberculin skin test is fallible and can miss infected animals. “Producers who buy cattle, particularly high value breeding stock, should be prepared to pay for them to be tested twice within 60 days of arrival.”

But he acknowledges the poor accuracy of currently available tests means biosecurity can fail to stop a new farm becoming infected. In his view priority should be given to cleaning up TB in newly infected areas before they become hotspots.

“Whenever herd breakdowns occur, the resources should be available to ensure reactors are valued and removed before they can infect other cattle or local wildlife carriers,” reckons Mr Howie.

Producers should also be encouraged to follow the example of his client and use their husbandry skills to send non-reactors exhibiting hard to diagnose symptoms for compensated slaughter.

“I have other clients who have picked out animals with negative results, but were found at the abattoir to have lesions.”

The latest DEFRA statistics show there were 2461 new herd breakdowns in Great Britain in the first nine months of 2004, and 48% of these were later confirmed by post mortem examination or by laboratory culture.

But a total of 4403 herds were under TB restrictions at some time during the period and September ended with 3296 herds, or 3.54% of the national cattle herd, operating under TB control regulations. This figure included some of the 3288 herds which testing was overdue.

On average, the number of reactors involved in each TB incident was 3.1, and between January and the end of September 14,445 cattle were slaughtered as reactors.