Concern is growing over wild sheep that have been grazing on the Cooley Mountains.
They are within the surveillance area established following the discovery of two cases of foot-and-mouth in Co Louth.
The outbreak was confirmed at Proleek, near Jenkinstown, on a farm located within the earlier exclusion zone established following an outbreak of foot-and-mouth in Co Armagh.
It is the first confirmed case of FMD in the Republic during the current European crisis.