It's a disgrace and all those involved should be prosecuted. And no, don't sell me this story saying it comes from Europe and it's traceable. That is bullshit! Europe is a big mess and half of it is full of corruption and organized crime and mafia.
Start passing laws to force supermarkets to buy locally and stop risking peoples lives by buying in places where they have no way of knowing where the meat comes from or who is actually sourcing it.

And let me tell you this: YES, IT IS CONTAMINATION. Horse meat nutrition wise is not the same as beef. In some areas it's much stronger nutritionally and it might do harm to some people eating it as beef. Horse meat has twice as much vitamin b12 and twice as much iron!