First, bovine tuberculosis is a disease that evolves very slowly, and it takes a lot of time for an animal to be infected. We have to go back five years to see whether the animals that joined the herd or left it during that period of time were infected. If the bacteria infects an animal today, it can take up to two, three or four years before the animal begins to show clinical signs of the disease.
Secondly, once we know an animal is infected, we inventory all of the animals of more than one year of age on the primary farm. Before that, we autopsy the contaminated animal to establish the pathology and confirm the case. We then do laboratory cultures of the bacteria, which take about 14 to 16 weeks. The process is long. There are three or four tests to detect bovine tuberculosis, but none of them on their own are sufficient to diagnose every animal; they have to be combined.