I am told, but cannot quote the actual Bulgarian AKT or Law that the dog owner is responsible in such cases and can go to jail.
However, proving who owns the dog, (it'll get quickly disowned under such circumstances) is another thing.
I find that the 'working' Karachchans that are meant to be with their Shepherd and Sheep can sometimes be far from where they're meant to be. My dogs have had the odd run it with the 3 that roam around here and it cost me 70 Lev in Vets fees to have my female dog sown up and injected.
I told the Shepherd on his return that the next time I see them over on my territory, I'd shoot them. Can't say as it has made much difference although, now I'm in good relations with the Sheep owner and he keeps the sheep and their shepherd well away from my property now.
Worthwhile doing the Tetanus as already suggested. Not sure about Rabies, but perhaps you should check with a Doctor or a Vet first. It used to be some painful course of injections in the stomach, but I understand those days are now passed.
I still prefer a stout walking stick when out with the dogs, I defy anyone to withstand a whack over the head with it.