On Monday, I wrote about core vs non-core vaccines for dogs and cats. Today I want to give more details about the core vaccines for dogs, which include canine distemper virus, parvovirus, adenovirus, and rabies virus. First, here’s a quick primer on these four viruses and the diseases they cause.
The Big Bad 4
Distemper Virus: this virus is closely related to the measles virus that infects people. In the U.S., most cases of distemper involve puppies who have not been immunized against the virus. An infected pup has a sticky discharge from their eyes and nose, a fever that comes and goes, a cough that often develops into pneumonia, and a poor appetite. Later, the pup will begin to vomit and have diarrhea and have hard callouses on the foot pads. Many pups will die at this stage. If the puppy survives, 1-3 weeks later he or she will experience seizures, tremors, loss of balance, and weakness. Dogs that survive the neurologic phase of the disease often have life-long side effects, such as thickened pads on their feet and enamel erosion on teeth, and may experience life-threatening, progressive neurologic disease.
Parvovirus: nearly every group of mammals has a parvovirus that will infect them. Luckily, dog parvovirus only infects canids, and human parvovirus only infects people. In 1978, the canine parvovirus-2 appeared and caused deadly consequences. Infected dogs shed huge numbers of virus, which is hardy in the environment. In 1978-79, no dogs had immunity to the virus and vaccine was in short supply. Many dogs were infected and died. Additional mutations have occurred, and we now have CPV-2a, CPV-2b and CPV-2c. Puppies infected with parvovirus have extreme vomiting and diarrhea that leads to extreme dehydration. There is no effective anti-viral drug and treatment involves supportive care, including IV fluids, antibiotics for secondary bacterial infection in the gut, and anti-nausea medication. Puppies are generally hospitalized for up to 5-7 days.
Adenovirus: In dogs, canine adenovirus-1 causes a disease called infectious canine hepatitis, sometimes referred to as “blue eye” due to clouding of the cornea caused by the virus. Dogs infected with CAV-1 experience loss of appetite, lethargy, fever, discharge from the eyes and nose, extreme redness of the gums, and occasionally vomiting. Ten to thirty percent of dogs will not survive the infection. Another adenovirus, CAV-2, is one of the viruses involved in infectious tracheobronchitis, or kennel cough, which is rarely fatal. Interestingly, the vaccine against CAV-2 provides protection against CAV-1, so these days we only give CAV-2 vaccine to dogs.
Rabies virus: as I mentioned in my post last week about rabies vaccination, wildlife, namely skunk, bat, raccoon, fox, and coyote, are most commonly responsible for exposing pets and people to the rabies virus. Although it may take a long time from exposure to the virus to development of symptoms, once symptoms have begun, death occurs within 10 days. The average time between bite to detactable virus in the brain is 20-30 days. The virus travels from the bite location along the nerves, and after it reaches the brain, it is present in saliva and other body secretions. Infected animals die within 5-7 days after the virus reaches the brain.
Core Vaccine Schedule
Hopefully you are still reading after the rather morbid description of these diseases! You get the picture that these four viruses are nasty and can definitely kill our beloved dogs, right? Vaccines were developed for very good reason, and my older veterinary colleagues can tell some sad stories about dozens of dogs succumbing to distemper and parvovirus outbreaks 30-40 years ago. I don’t think it was so crazy in the 70’s and 80’s, in the midst of the outbreaks, to administer vaccine to dogs every year. Today, though, we have much better control over these viruses (and they are all still around, don’t be fooled) as well as good scientific evidence that our vaccines create immunity that lasts much longer than one year. This is why the vaccination interval has been updated. It’s common sense! So here is the much-awaited schedule:
Distemper, Parvovirus, and CAV-2 vaccine
- For puppies < 16 weeks of age: vaccinate at 8, 12, 16 weeks of age
- For dogs > 16 weeks of age receiving first dose: single dose of vaccine
- for puppies who received initial series by 16 weeks of age, booster 1 year later, then every 3 years*
- for dogs who received initial vaccine after 16 weeks of age, booster every 3 years thereafter*
*The 2011 AAHA Canine Vaccination Guidelines state that vaccines for these viruses produce a protective immune response in dogs for at least 5 years.
- Puppies under 16 weeks of age: one dose between 12 and 16 weeks
- Dogs over 16 weeks of age: one dose
- All dogs must receive a booster within 12-14 months after the initial dose; thereafter booster every 3 years
The Wrap Up
Without a doubt, vaccines have saved many dogs’ lives and have helped to greatly reduce the incidence of rabies in people. The pressing question now is why dogs are still being vaccinated on an annual basis when national guidelines and scientific evidence recommend otherwise. Next week, we’ll look at non-core vaccines for dogs and core vaccines for cats. During the last week in January, we’ll finish up with non-core vaccines for cats, titer testing in dogs and cats, and my personal recommendations for vaccinations.