Your dog's natural curiosity and his prey drive encourage him to investigate anything that moves, including some living creatures who can harm him. In the event that an animal bites your dog -- even if the biter is not a predator, such as an opossum -- you need to handle it quickly and appropriately to minimize the potential damage the bite can cause.
Opossums are notorious for playing dead when frightened; but if your dog corners a opossum who's not playing dead, it is normal for the opossum to try to defend himself. Opossums have relatively few defenses, so you can expect your dog to emerge from a fight with an opossum sporting bite marks as well as claw marks.
After decades of being warned about the rabies risk associated with wild animal bites, it is only natural for you to wonder if an opossum bite will give your dog rabies. The good news is that your dog faces almost no rabies risk due to an opossum bite. For one thing, your dog should be vaccinated against rabies. The rabies vaccine protects your dog from the disease and is legally required in many areas of the country. For another, according to the Humane Society of the United States and the Missouri and Illinois Bi-State Wildlife Hotline, opossums are largely resistant to rabies and almost never carry the disease. The odds of a healthy, vaccinated dog getting rabies from an opossum bite are next to none.
The real threat your dog faces from an opossum bite wound is the chance of infection. An uncleaned, untreated bite wound can contain plenty of dirt and bacteria. Without treatment, the bite wound may become infected and cause complications including fever, vomiting and diarrhea.
If your dog gets bitten by an opossum, or any wild animal, your best option is to take him to the veterinarian for an exam and treatment of any injuries. Your veterinarian will be able to medicate the wounds and prescribe any antibiotics or painkillers he feels your dog needs as a result of the wound.