The most frequent sign of rabies in dogs is an unexplained change in behavior, usually when a normally friendly dog turns aggressive or acts strangely for no apparent reason. A wild animal’s reaction may be entirely different. He may act tame and unafraid when approached by people. Once a rabid animal begins to exhibit abnormal behavior, which could take two to six months after contact, it has begun an irreversible process that will only end with his death, which will occur in a matter of days. There is no way to save his life because there is no cure for rabies. Not every dog, indeed not every animal (including humans) that is exposed to a rabid animal will contract rabies.
If you suspect your dog may have contracted rabies, be extremely careful and avoid all contact with him. Isolate him and call your veterinarian and animal control immediately. By law, you must make these notifications to protect the public. Let your doctor know if your dog has been vaccinated. If you live in Canada, you must also call the local police and the health control office. The best way to protect your dog from rabies is to follow a rabies vaccination protocol as established by your local government or as recommended by your veterinarian.
Source: Adapted from the American Animal Hospital Association