What Does the Vet Say? - April 2025
Bovine tuberculosis (bTB) has increased in prevalence on Irish farms over the past few years, causing economic and personal stress for livestock owners affected: “It is a huge stress for farmers going through a TB breakdown, and it is an increasing problem,” says Joris. “We see herds that never had a problem suddenly coming up with reactors. I wouldn’t say it’s getting out of control, but it’s costing the industry a lot of hardship and a lot of money,” he adds.
It has also led to the Department of Agriculture, Food and the Marine (DAFM) to state that the rising numbers recorded since 2017 highlight the ‘continued need for urgent action by all stakeholders’. Its provisional data, at the end of December 2024, showed that 41,630 reactors had been identified and 6,142 herds were restricted on a 12-month rolling basis. At that time, herd incidence was (provisionally) 6 per cent. In 2016, that percentage was 3.27.
Financial support
Tirlán has introduced a €5m support measure to assist its milk suppliers affected by TB outbreaks. Joris outlines the details: “It is part of an overall TB support package that Tirlán has launched to provide cashflow support, because farmers with a TB breakdown lose both cows and milk production. It will assist farm cashflow while farmers wait for Department of Agriculture supports to kick in. It’s basically a pre-payment on future milk production. We’re allocating it to farms that have at least five per cent of the adult dairy cows and pregnant replacement heifers coming up as reactors.
“The measure starts for herds that have had a breakdown since January 1, 2025 and it will run for two years. We’ve put an end date of December 2026 and we will review whether we need to extend this or tweak it. It’s a voluntary scheme and the money will be taken back out of the milk payments from 2027 if you entered the support programme in 2025.
“Over 2027 and 2028 the money would be refunded to the co-op through payment deductions over several peak production months. There are special concessions for new entrants hit by TB as the financial impact is even greater for them at a time of high investment in their businesses.
TB drivers
TB is caused by caused by the bacterium, Mycobacterium bovis and discussing the vectors that are driving the spread of TB in Irish livestock herds, Joris says: “I don’t need to explain that this is a very complicated disease. If it was simple, we would have solved it decades ago. There is obviously a wildlife reservoir, but the cattle population is also a reservoir with cattle moving into areas where TB wasn’t prevalent before. They might get detected and get taken out of the herd, but by then TB might be established in that locality and that’s when the wildlife becomes an important factor in keeping TB in the area.
So, it’s that balance between where TB is coming from, and there are various factors, including trading of animals, biosecurity, and wildlife,” explains Joris. Upgrading biosecurity on farms has an important role to play in keeping the disease at bay in some instances, he says, adding: “And it could also be as simple as upgrading some of the hardware, fencing, gates and so on that are no longer fit for purpose.”
Susceptibility to TB
We are seeing TB outbreaks in herds previously clear for many years. Joris sheds some light on why this might be the case: “The animal’s immune system is very important [in this regard]. Certain animals or certain herds might be more resistant to TB than others but if the exposure is high enough, they will get it. There is even a genetic component identified, and the Irish Cattle Breeding Federation has started including that in the EBI. From the health sub-indexes you can select sires that deliver proven higher resistance to TB in their offspring. If you are in a higher risk location, it’s worth considering those sires as part of your bull selection process.”
And there are other scientific developments ongoing including the potential role of vaccination against TB but, Joris says, the major problem with this is that you can’t differentiate between a vaccinated animal and an infected animal. He elaborates: “From an international trade perspective, it’s just not acceptable that we can’t distinguish between an infected and a vaccinated animal. There’s been a lot of money spent on research in developing a marker vaccine, but we’re still not there. If that were to happen then we’d be in a situation where we could vaccinate animals and be able to say here is a clear animal and she’s vaccinated, she’s protected against TB. We’re not there, but the research is ongoing and hopefully one day they’ll crack it.”
Genetic variation study
The results of a new study – published on World Tuberculosis Day, which took place in March – has shown a genetic link to bovine TB susceptibility. Researchers at University College Dublin (UCD), University of Edinburgh, and ETH Zurich identified several key genes and pathways involved in the bovine response to M. bovis. Professor Eamonn Gormley, director of the bTB diagnostics laboratory, at the UCD School of Veterinary Medicine, said this is the first study that ‘directly links genetic variation underpinning bovine TB disease susceptibility to the activity of individual genes’. “Importantly, it signposts future research to develop new diagnostics and tools for breeding cattle with enhanced disease resilience,” he said.
Keeping global diseases at bay
Joris, a former lecturer at the UCD School of Veterinary Science, widened the discussion to more exotic diseases that have not yet, fortunately, reached our shores: “Bluetongue would be hugely impactful if it entered Irish livestock. We’re coming out of what is the quieter time for the midges that carry the bluetongue virus. As the weather warms up again the risk of infection heightens. It is increasingly prevalent on the continent and has reached the UK. If the prevailing wind keeps the midges off the island, we’ll be okay from that perspective. But there’s still a risk of animals that are infected being brought into the country. If we import animals from the likes of France or Belgium, that greatly increases the risk of the virus establishing itself here. Infection risk factors include biological material such as embryos and semen.”
Avian flu is a huge problem in the US and there have been some incidences of it here, particularly in the northern part of the island of Ireland. Joris looked at the risks involved: “At the moment, the impacts in this country are limited to the poultry sector, where flocks must be housed under current regulations. But what we’ve seen in the US is quite worrying. Avian flu there has gone from being solely a bird problem to now affecting the dairy herd. It’s spreading through the milk between cows in the parlour, the way we might see mastitis spread," he says.
There are now nearly 1,000 herds across the US infected with avian flu. Pasteurising milk kills it, so there’s no risk from a consumer perspective. But it’s really worrying that in the US a strain of avian flu has jumped species from birds to bovines, Joris says. Reports of foot-and mouth-disease in some parts of Europe was also recognised as a concern: “There was a single case in January in Germany. It was limited to a water buffalo farm, but a few weeks ago there was another case reported on a large Hungarian livestock farm. Information on the precise strain was not immediately available, but equally worrying is the fact that the authorities do not know where the disease originated or how it got onto the farms. The latest Hungarian case is in the centre of the country and none of the surrounding countries have an infection. "Foot-and-mouth disease is very infectious. It spreads very quickly between susceptible animals. It can be carried by people and even in food waste. It’s very easy to transport the disease from somewhere outside the EU in food material that then is chucked out and wildlife might pick it up. We must be very cautious with this and we’re following the cases in Germany and Hungary very closely.”
Additional reporting: Bernie Commins.