Answer
The preferred view is that dogs are not napaak, only their saliva in napaak.
We are unaware of the ruling concerning dogs in the previous nations, however the saliva of dogs was classified as napaak(inpure) for us, from the time Nabi (sallalahu Alaihi wasallam) classified it as such.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai