The Minister for Agriculture is expected to decide today whether to extend the culling of animals on the Cooley peninsula in Co Louth in an effort to avoid the spread of foot-and-mouth.
Mr Walsh said yesterday he was awaiting veterinary advice and would make a decision within 24 hours.
Speaking on RTE he said the situation at present was that all cattle and sheep had been culled in a 3km zone around Proleek, Co Louth, where an outbreak of the disease was confirmed last week.
Asked whether he would extend the cull right across the Cooley peninsula, he replied: "That will depend on the veterinary advice and the co-operative effort between North and South, which I might say is excellent."
Describing his reaction to last Thursday's news of a positive case in the area, Mr Walsh said: "It was a real shattering blow because we had gone through more than three weeks of trauma and highs and lows and suspect cases and so on, and then we felt we were almost there, almost at the line."
The Department was still treating the outbreak as a secondary one, related to Northern Ireland's only positive case at Meigh, Co Armagh.
The Department's investigation unit and the Garda were intensively following up every possible lead to explain how the disease spread, he said.
Reacting to the Taoiseach's comments at the weekend that controls at ports and airports in the North needed to be improved, Mr Walsh said he was confident all necessary measures had been taken there.
"As far as I am aware we are getting the fullest and most total co-operation possible from the North of Ireland, and [Agriculture Minister] Brid Rodgers is outstandingly helpful in relation to all of this.
"But in any measures which you put in place to find an invisible, virulent organism, of course things can be tightened up."
On who should be compensated for financial losses arising from the crisis, the Minister said: he had "the very greatest sympathy" for affected businesses, but the first priority was to contain this disease and to seek to ensure that it did not spread to the entire country.
"After that we will have to look at how people were discommoded and the inconvenience and the loss of income for them."
