While snake bite is rare in humans with dogs it is a different matter. Dogs have a number of different reactions to snakes ranging from being scared of the snake to attacking it. The ideal reaction is to bark at the snake from a safe distance but unfortunately the most common reaction is to attack the snake. A dog attacking a snake is not a conscious effort to protect the family, rather some dogs will simply kill any small animal within reach. Unfortunately for the dog some animals can fight back.
Symptoms of a dog being bitten vary from the dog being un-coordinated and looking drunk to vomiting and bleeding from the lips and anus. It is normally very difficult to locate the actual bite site. The absolute best thing to do if you suspect envenomation is to keep the dog quiet and get it to a veterinarian as soon as possible. Veterinarians are normally pretty good at treating dogs as many have a lot of practice at it. Unfortunately treatment can be expensive as a vial of antivenom is around a thousand dollars, and more than one vial may be needed, and vet fees can mount up dramatically if intensive care is required.
There are a number of steps you can take it mitigate the risk of your dog getting bitten :