Parvovirus is usually diagnosed in young dogs that have not received their full complement of preventative vaccines. Protecting puppies from parvo is a race between declining maternal immunity (antibodies they receive from their mom), exposure to the virus, and vaccination. When maternal immunity is high, it deactivates the vaccines. As maternal immunity begins to fade, vaccinations become effective, but since we don’t know how much maternal immunity a puppy has received and when it begins to wane, we have to vaccinate multiple times to keep the window when a puppy is susceptible as narrow as possible.
Veterinarians typically recommend that puppies be vaccinated for parvo starting at 7-8 weeks of age (earlier vaccines will almost surely be deactivated), and then every three weeks, for a total of three (sometimes four) vaccinations. Most vets then recommend a booster at the first annual checkup and then one every three years from that point on. Checking a dog’s titer — the level of antibodies to parvovirus in the blood — is an alternative to giving routine boosters in adult dogs. At some point, vaccination may no longer be in the pet’s best interests because of advanced age or illness; this should be determined on a case by case basis.
The recent outbreak of parvo in adult dogs surprises me for a couple of reasons. First, it is so easy to prevent. A vaccine booster or titer check every three years should do the trick in most cases. I’m sure economic concerns played a role for the owners of these dogs in Mesa County, but this a classic case of an ounce of prevention being worth a pound of cure. While it is best for owners to schedule an appointment with their veterinarian for a checkup and any needed preventative care at least annually, a combo vaccine that offers protection against canine distemper, infectious canine hepatitis, canine adenovirus type 2, canine parainfluenza and canine parvovirus is widely available over-the-counter for about $6.00. According to one pet insurance company, their average claim for treating parvovirus is $717.59. Even with appropriate therapy, the disease can be fatal.
I also thought that adult dogs would be a bit more resistant to parvovirus than the reports from Mesa County seem to show. Parvo is widespread in the environment, and exposure to low levels of the virus in an otherwise healthy, previously vaccinated adult dog should act as a natural "booster" of sorts. I don’t have the details of these cases. Maybe these dogs weren’t well-vaccinated previously. Maybe they weren’t otherwise healthy, or they were coming across massive doses of the virus that overwhelmed their tenuous immunity. Whatever the reason, I’ll certainly be using this outbreak as evidence as to why adult dogs need to receive their boosters or have their titers checked on a regular basis.
Dr. Jennifer Coates