Tackling a persistent TB breakdown
By the Animal Health and Veterinary Laboratories Agency (AHVLA)
Persistent TB breakdowns can have a devastating impact on farming businesses. To help farmers regain their Officially TB Free (OTF) status as quickly as possible AHVLA has recently introduced a more tailored and hands-on management approach to tackling these long-term breakdowns.
Movement restrictions are put in place when TB infection is suspected in a herd. If TB is subsequently confirmed the herd loses its OTF status and movement restrictions remain in place until the herd passes two consecutive skin tests.
When a herd has been under movements restrictions for more than 18 months because of infection this is classified as a ‘persistent TB breakdown’.
Richard, one of AHVLA’s vets, has been investigating a persistent TB breakdown in the South West of England:
“The farm I want to talk about has been under movement restrictions for nearly six years. At first losses were not extreme: 13 cattle between January 2008 and December 2010. Then in 2011 and 2012 the number of reactors escalated to 60 each year, and finally in 2013 losses hit a catastrophic 159.
"Jack and Jill (not their real names) run a traditional dairy farm, with a substantial beef enterprise alongside. Their total stock exceeds 1100, with 300-400 cows in milk at any one time. Having had a manageable TB problem for some years, in 2011 the abattoir started reporting visible lesions in some fat cattle sent for slaughter. Laboratory culture of these lesions subsequently confirmed the presence of Bovine TB.
"The alarm bells really started to ring that autumn when two dead badgers were found in a corner near the beef finishing shed. A TB skin test in November revealed 35 reactors, 29 of which showed visible lesions. Fresh badger tracks in some wet concrete showed a continuing presence of these animals on the farm.
"Having undertaken a Disease Report Investigation at the beginning of the breakdown, assessed the post mortem results and reviewed cattle movements onto the farm I concluded that the infection had probably been brought into the herd by wildlife. At this point I discussed bio-security with the farmer and his wife to reduce potential cattle contact with badgers. Jack took positive action, erecting a new cubicle shed and an extensive 1.5 metre concrete panel barrier to make their entry to the farm yard much more difficult.
"With these measures in place a subsequent survey with infrared motion activated cameras showed no badgers in the farm yard over an eight week period. But the farmer and his wife were unaware that their prize home-bred bull had not only contracted the infection but was spreading it. Nobody knows when he succumbed to this disastrous disease or how many of his ‘wives’ had been infected at the same time. Maybe he was not immediately detected by the TB skin test, but whatever the time scale, open purulent places in his lungs ensured he was a danger to any cow in which he took an interest. He finally became a skin test reactor in early summer of 2013, but that did not prevent the slaughter of a further 214 cattle that year, some also with spreading infection in their lungs.
"So where are we now? We have a positive farmer who acknowledges the help he has had from AHVLA and his own private vet. He thinks the worst is behind him. Reported TB from the abattoir has become a rarity and his young cattle were free from infection at the last test. The lingering infection amongst the cows is, hopefully, a reflection of the high level of disease initially and not ongoing infection. Both Jack and Jill hope a clear TB skin test in 2014 is on the cards.
"With disease reducing there is an air of optimism about and I leave the last comment to Jill. In her words:
“The way forward for us is to continue to TB test, promptly remove any TB reactor animals, and be ever vigilant in watching the health and behaviour of our cattle, all the while keeping our biosecurity measures on farm under review. Any signs of coughing, weight loss or unexplained ill-health must be investigated to make sure the animal is not a carrier that has gone through the test undetected.”