Introduction
Most veterinarians agree that all dogs should be vaccinated against those diseases that are widespread, cause serious illness, and/or are highly contagious. In addition, other vaccines may be recommended based on the risk they pose to individual dogs. While many pet owners believe vaccines produce 100% protection in all dogs, this is not always true. Some vaccines will protect most dogs, but others may only reduce the severity of clinical signs.
Core Vaccines for Dogs
Canine Distemper
This disease, caused by the morbillivirus (a paramyxovirus), causes respiratory, digestive, and nervous system signs in affected dogs, and can be fatal in about half of unvaccinated dogs. Recovered dogs may have permanent damage to their nervous systems. The chronic form of the disease can lead to hard pad disease, a chronic thickening of foot pads, and encephalitis, an inflammation of the brain. Some dogs that acquire the virus show no signs or very mild signs, but can easily infect other susceptible dogs. Unvaccinated dogs are at a 350 fold increased risk of contracting this highly contagious disease which is spread by discharges from the nose and eyes of infected dogs.
Infectious Canine Hepatitis
This virus is caused by a viral agent, the canine adenovirus CAV-1, and is spread through infected urine. The virus may cause liver failure, eye damage, respiratory problems, and can be fatal. Commonly encountered clinical signs are vomiting, abdominal pain, diarrhea, and occasionally coughing. It is actually CAV-2, a closely related virus that is used in the vaccine because it is less likely to cause side effects and is cross-protective.
Canine Parvovirus
The disease is caused by parvovirus of types CPV-2, CPV-2a and CPV-2b. Infection is both serious and widespread in dogs. Signs, which include severe vomiting and diarrhea with blood, result from the virus damaging the gastrointestinal tract. The disease is spread via infected feces. Death in as early as 48 to 72 hours can occur in some dogs, although sudden death can also occur. Parvovirus infection may also cause bone marrow suppression and myocarditis (inflammation of the heart muscle). This virus is very resistant in the environment and is easily carried around on people’s shoes and other objects, leading to virus transfer. For this reason, even indoor hi-rise apartment dogs that never go out require protection. Vaccination is the most effective protective strategy for all dogs, young and old.
Canine Parainfluenza Virus
One of the causes of kennel cough, this respiratory disease is caused by a parainfluenza virus. Characteristic features of kennel cough are a hacking cough, discharge from the nose, and occasional fever. While the parainfluenza virus on its own produces mild symptoms, especially a cough, it is frequently present as a co-infection with other kennel cough agents.
Rabies
All mammals, including humans, are at risk of contracting rabies, which is almost invariably fatal. Rabies is sometimes called the great pretender because signs are so variable in animals. Rabid dogs may display a "dumb" form, characterized by listlessness, weakness, and paralysis, or the "furious" form of rabies characterized by abnormal aggression. Less commonly, dogs may just have signs of drooling with their tongue hanging out. In areas where risk is high, vaccination of dogs and cats is mandatory. Even dogs that do not go outside much should be vaccinated: rabid bats can fly into homes, and rabid wildlife such as skunks and raccoons can enter a fenced yard.
Research shows that animals with rabies can shed the virus (infect people) before the signs are obvious, so avoid close contact with a stray. Instead, contact the appropriate authorities to rescue it for you.