The Animal Health Board is responding to a bovine tuberculosis (Tb) infection in a dairy herd in the Awanui area, the third case in that area within three years. Infected cows found in two herds in 2009 had been destroyed, and the herds had since tested clear.
Now positive reactors in a third herd, which was not one of those involved in 2009, had been destroyed.
The board's northern North Island regional co-ordinator, Frank Pavitt, said last week that the exact source of the infection had yet to be determined, but there were number of possibilities.
Checking wild animal populations, especially possums and pigs, was already under way to see if the disease was present in the surrounding area, but while possums were the main source of Tb infection in farmed cattle and deer they had never been identified as a cause in Northland.
Infection could also arise as a result of importing infected cattle, and hunters introducing deer or pigs from other areas to provide sport.