Investigations into the suspected BSE case on a dairy farm near Louth village are considering the possibility that the five-year-old cow may have contracted the disease from feed eaten years earlier.

The Rotbunt cow, a rare pedigree breed is from a farm well-regarded for its standards.

Bovine Spongiform Encephalopathy, commonly known as Mad Cow Disease, is a fatal disease that attacks the animal’s brain and central nervous system. Some 1,659 cases have been reported in Ireland since the first case was diagnosed in 1989. That outbreak was linked to animals eating feed that contained contaminated meat-and-bonemeal.

The number of cases fell dramatically after the feed mix was banned and other control measures were introduced. There were no cases of BSE reported last year, for the first time since 1989.

Most animals that died from BSE in recent years were old and had eaten feed containing meat-and bonemeal years earlier, so a case involving a five-year-old cow is unusual.

However, because animal feed can adhere to the sides of feed silos, investigators are considering the possibility that old feed containing meat and bonemeal may have hardened and fallen into new feed.

The suspected BSE case is on a farm that had a BSE outbreak many years earlier but investigators don’t believe the cases are linked.

The Department of Agriculture said it was tracing the animals born at the same time as the affected cow and was tracing her calves and testing them for the disease.

Both groups of animals will be destroyed as a safety measure.

The Government stressed it was an isolated case and moved to reassure consumers that there was no food safety risk. Taoiseach Enda Kenny said it was “ a disappointment to put it mildly, given the very rigid standards and the very high level of integrity and credibility that we have in our systems that this has come to light”.

Minister for Agriculture Simon Coveney there was “absolutely no human risk” as the animal had not entered the food chain. “What we have is a very robust system whereby any animal that dies on a farm gets BSE tested, so no animal can die in Ireland, on a farm...without being tested for BSE.”

He said it was ironic that this should happen just one week after Ireland’s BSE status was upgraded from “controlled risk” to “negligible risk” status.

He also noted that Ireland had “controlled risk” status when it got the ban lifted on beef exports to the US, China and Japan so if Ireland reverted to that status it should not affect trade.

ICMSA president John Comer said it was important that people did not over-react. “We would doubt whether this incident could threaten the kind of market penetration and international recognition that Irish beef has been achieving over the last number of years,” he said.

This was echoed by Bord Bia chief executive Aidan Cotter who said the case was “unfortunate” but he was confident it would not adversely impact on the reputation of Irish beef among its European and international customer base.

IFA president Eddie Downey said he believed it was a random and isolated case and the fact that it was discovered showed the effectiveness of the monitoring and control systems.

“A random case is not unusual in the context of the robust control systems we have in place for all diseases.”

Fianna Fáil spokesman on agriculture Éamon Ó Cuív said it was essential that immediate action was taken to isolate the cow and the farm. “All measures must be utilised to ensure that the herd’s status is protected and that a comprehensive plan is put in place to limit exposure to any potential case.”

BSE control measures were stepped up in the mid-1990s when variant CJD, a fatal brain disease in humans, was linked to BSE. All animals presenting for slaughter are examined by veterinary inspectors and after slaughter animal tissue shown to be capable of transmitting the BSE agent is removed and destroyed.