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Focus

Focus - Herd health - March 2020

Slight increase in national bovine TB stats

The Department of Agriculture, Food and the Marine recently released the national herd incidence for bovine tuberculosis, which showed that, as of December 31 2019, it stood at 3.72%, marginally up on 2018 (3.51%) and 2017 (3.47%)

Since the beginning of 2019, 3.72% (4,060 herds) of all herds tested for bovine tuberculosis (bTB) have experienced a new breakdown, ie. at least one animal tested positive for bTB. Herd incidence for 2019 was the highest recorded since 2013 and marks the third successive year of increasing bTB levels.
Figure 1 shows bTB levels in many areas overall are low but there are areas with higher levels of bTB in the north-east of Ireland (Monaghan, Cavan, Louth and North Meath) as well as parts of Clare, Cork, Wicklow and some other districts.
The number of reactors identified through a combination of skin testing and gamma interferon testing (GIF) in 2019 was 17,058, a decrease of 433 from 2018 (about 2.48%). GIF testing can identify bTB infection at an earlier stage than the single intradermal comparative tuberculin test (SICTT), which is used for the annual round test. Therefore, when used appropriately, GIF testing can reduce the chances of leaving residual infection in a herd after de-restriction. By removing more infected cattle earlier, the risk of re-infection will fall, according to the DAFM.
Over the last 10 years, herd incidence has fallen from just under 5.09% in 2009 to 3.72%, and reactor numbers have fallen from over 23,805 to 17,058. This is due to the cooperation between farmers, private veterinary practitioners and DAFM officials. However, continuing efforts are needed from all stakeholders to reverse the increase in national bTB incidence over the past three years and to reduce levels in 2020, the DAFM has said.

What is driving the current trends in bTB levels?
While Ireland has far lower levels of bTB than in previous decades, this trend has reversed over the past three years. The reasons why this is happening are multifactorial and often relate to local factors. It is likely that the expansion of the dairy herd since 2015 has played a role in this, since dairy herds, larger herds, and herds which introduce more cattle are all more at risk of bTB breakdowns. Fifty-two% of all bTB reactors in 2019 were in dairy herds, while there were approximately 2.8 million farm-to-farm cattle movements in the same year.
Risks must be addressed by national policy changes and by actions at farm level, according to the DAFM.
“As we enter into the decade towards 2030 this is a pivotal year for Ireland’s bTB eradication programme and it is critical that, through working in partnership and joint ownership, all stakeholders take the necessary actions to reduce disease transmission, protect herds from new infections, and clear bTB from restricted herds.”

Advice for herd keepers to reduce their risk of bTB?
These recommendations are part of the DAFM’s efforts to help farmers tackle bTB.
1. Reduce the risk from badgers:
• If badger setts or latrines are present on grazing land, fence them off with electric fencing to keep the grazing cattle away. This is to avoid cattle encountering contaminated soil;
• Do not feed cattle concentrates spread on the ground, and try to avoid spilling feed on the ground, as badgers and deer may consume it and contaminate any leftovers which cattle may subsequently eat. Do not store feed, eg. beet in an area accessible to wildlife;
• Feed cattle in raised troughs;
• Wildlife-proof farm buildings by covering the lower part of access gates to sheds so wildlife can’t get through; and
• Advise DAFM of any badger setts on the farm

2. Reduce the risk of contiguous spread:
• Boundary fences should be well maintained, particularly if neighbouring land has a herd which has had bTB in the recent past; and
• Mixing groups of cattle that are normally managed on separate land fragments should be avoided.

3. Reduce the risk of residual infection:
• Cull any cattle that ever tested inconclusive, even if they subsequently re-tested negative; and
• Consider culling any cattle which were in the herd during any previous bTB breakdown, particularly older cows.

4. Reduce the risk of introducing infected cattle:
• If purchasing cattle, reduce the risk by sourcing them from a herd which has not had a bTB breakdown in recent years; and
• If purchasing cattle at a mart, cattle with a more recent bTB test date are likely to be at less risk than similar cattle which were last bTB tested many months ago.

5. General advice:
• Ensure good quality bTB testing facilities are available – the vet should receive any assistance needed;
• Farmers engaged in contract rearing should consider their biosecurity measures and how they would manage a bTB breakdown affecting the contract arrangements. Avoid feeding unpasteurised milk to calves;
• Effective cleaning and disinfection of any areas where reactors were kept is essential and will reduce the risk of environmental contamination infecting other cattle;
• If sharing machinery, trailers, etc. with other farms, minimise the risk of bTB spread through environmental contamination by cleaning and disinfection;
• When breeding, select bulls which are genetically more resistant to bTB and avoid those more genetically susceptible. The Irish Cattle and Beef Federation (ICBF) provides bTB scores for bulls on their website, using a traffic light system; and
• Advice videos can be found on the DAFM’s YouTube channel, or at www.agriculture.gov.ie

Regional

  • The herd incidence in Monaghan of 7.02% and Cork North of 6.12% (which is significantly higher than the national herd incidence of 3.72%) are particularly relevant as they have higher cattle densities than other counties and this therefore indicates greater amounts of bTB.

  • Cork north had the highest number of reactors at 1,993. Monaghan had the second highest at 1,336 followed by Clare with 1,190 reactors.

  • A targeted, high-impact bTB control plan has been in place in Monaghan and parts of Cavan and Clare during 2019 in collaboration with stakeholders. Its focus is to identify and eradicate disease in those areas as quickly as possible.

  • While Wicklow west had the highest herd incidence at 12.33% (380 reactors), this region has less than 0.5% of the national herd.

  • Limerick and Longford had the lowest herd incidence at 2.06% and 2.21%.