Whether diseases are reportable or not depends on multiple factors. These include whether it causes a lot of economic losses, or whether it is zoonotic, or a disease that could create a lot of impact on the general survivability of the industry and Canadians.
Then there is a list of reportable diseases dictated by the World Organisation for Animal Health, OIE, which binds us. Canada, being one of the 181 members, is basically obligated to report and also to take actions.
However, in terms of the reportable diseases specific to the provinces, the provinces may actually use it for statistical purposes or for management purposes. Federally reportable diseases might be different from the provincially reportable diseases.