The Department of Agriculture has confirmed a case of 'Atypical BSE' in an 18-year-old cow.
It was identified through surveillance of 'fallen' animals, who died on a farm in Galway.
The animal tested positive on a screening carried out at a department-approved, private laboratory over the weekend.
It was then subject to follow up confirmatory tests at the department's Central Veterinary Research Laboratory.
In a statement, the Department of Agriculture say: "There are no associated public health risks with this event - a comprehensive set of public health controls are in place and the animal in this case was excluded from the food chain and its carcase will be incinerated."
"The disclosure of this case of Atypical BSE does not have any impact of Ireland's current OIE BSE 'controlled risk' status or trade status," it adds.
Since 2006, the majority of BSE cases here have been diagnosed in animals that were over 12 years of age at the time.
But this case is the first confirmed since 2013, which was also seen in fallen stock.
There are two types of Bovine Spongiform Encephalopathy (BSE) - more commonly known as Mad Cow Disease.
There were several incidents of Classical BSE since the 1980s.
BSE cases in Ireland - last updated March 24th 2014 | Source: Department of Agriculture
This was associated with the feeding of meat-and-bone meal, where scientific evidence indicated BSE was acquired in the first year of life.
While Atypical BSE has been identified more recently, and is thought to occur spontaneously.
It occurs in older animals with a low incidence rate - having been first recognised in the early 2000s.
There have been 101 atypical BSE cases identified in the European Union from 2003 to 2015.
This compares to a total of 2,999 cases of classical BSE during the same period.
Back in February 2015, the US market re-opened to Irish products for the first time in 15 years.
This marked the end of an American embargo on European beef, which was introduced at the height of the BSE crisis.