Both cats and dogs are at risk of being bitten although young cats and oriental breeds of cat seem more at risk probably because they are more playful and inquisitive.
Most dogs will have a severe anaphylactic (allergic) reaction within the first 15 to 60 minutes after being bitten and will need immediate veterinary treatment. Cats will generally take longer to show signs. Its not unusual to have a "quiet" cat at night and wake up to a cat that cannot walk the next morning after a bite. The signs of snake bite include;
Dogs with acute anaphylactic symptoms will be salivating, may vomit, urinate, breathe rapidly, may be trembling, collapse and may have blue gums and tongue. These dogs will often die if they don't get immediate veterinary treatment.
Cats will generally be quiet at first, then after several hours will develop weakness and in-coordination in the hind legs which eventually progresses to the fore limbs causing a general flaccid paralysis (floppy cat). They may have dilated pupils. Often these animals are very frustrated and vocal.
Animals bitten by snakes require anti-venom. 50% of animals who don't receive anti-venom will die even with supportive therapy (intensive nursing on a drip). Anti-venom is best given as soon as we can, as early administration will save lives and reduce the costs of treatment as the animals improve more quickly. Animals may need more than one dose of anti-venom (if bitten more than once).
It is a good idea to keep your yard as clean as possible to avoid attracting snakes to your environment. Mow long grass, remove piles of wood and leaf litter. Snakes love rats and mice so keep compost bins covered and pick up any fallen fruit to discourage rodents. Snakes also seak out water so if possible keep water bowls indoors.