Why is it that a virus that infects humans, is not likely to infect a dog or a cat?

Most of the viral and bacterial infections are transmitted from dogs to humans by dog bite; however, other infections caused by protozoa have a fecal oral transmission. Cats can transmit Toxoplasma to people through their feces, but humans most commonly become infected by eating undercooked or raw meat, or by inadvertently consuming contaminated soil on unwashed or undercooked vegetables. Rabies is a viral disease that is spread through the bite of an infected animal. Hope I’ve helped ;)