The rabies virus is fatal once symptoms appear. Rabies vaccination is required by law at local or state levels because the disease is fatal to humans as well as dogs, raccoons, coyotes, foxes, skunks, cats, and other mammals.

Some veterinarians use three-year rabies vaccine; those in areas with disease outbreaks give boosters every year for maximum protection.

The American Veterinary Medical Association considers canine distemper to be the greatest single disease threat to the world’s dog population.

Canine distemper virus is fatal to 80 percent of the puppies and 50 percent of the adult dogs that contract it. Symptoms include congested lungs, nasal discharge, gunky eyes, coughing, weight loss, vomiting, and diarrhea. As the disease progresses, it attacks the nervous system, often causing partial or complete paralysis and seizures.

Distemper is highly contagious. Dogs can get the virus through the air, by direct contact with urine, feces, or secretions from infected dogs, and by contact with kennels, bedding, toys, or other objects that may hold the virus.

According to AVMA, “Some veterinary medical scientists estimate that practically every dog that lives to be a year old has had contact with the virus at some time. … Distemper is so prevalent and the signs so varied that any sick young dog should be taken to a veterinarian for a definite diagnosis.”

Most distemper cases appear in dogs less than six months of age and in old dogs that have not been routinely vaccinated. Once the dog is infected, there is no cure. Treatment is supportive; i.e., fluids are given to prevent dehydration and symptoms are treated, but the disease must run its course. Dogs that recover from distemper may develop hardened foot pads and nose leathers and have vision and nervous system problems throughout their lives. In addition to these consequences, puppies may also have mottled teeth from damage to developing enamel.

Distemper can be prevented by vaccination. Some university studies indicate that immunity lasts longer than a year after inoculation, but pet owners should discuss frequency of vaccination with their veterinarian. Generally, older dogs that remain at home may not need annual boosters, but dogs that spend time in training classes, grooming shops, day care centers, or boarding kennels; dogs that participate in public events; and dogs that compete at shows and trials should be vaccinated.

The North Carolina State University published a vaccination protocol in 2001 that “highly recommended” vaccination against distemper with a modified live vaccine but noted that, because some studies indicate that dogs are still protected for five years or more when challenged by the disease, “a booster vaccination of every three years among adult dogs is reasonable.”