Your veterinarian will soon have a new in-office test to help you make canine vaccination decisions. How useful that test will prove depends not so much on the test results, but on the questions veterinarians and pet owners expect it to answer.
The test, dubbed the Canine VacciCheck by its manufacturer, checks titer levels for three canine viruses: Canine Infectious Hepatitis (CAV-2), Canine Parvovirus (CPV) and Canine Distemper (CDV).
It’s not available yet, but its early marketing focuses on three uses:
Determining the vaccination status of dogs with unknown vaccination historyDiscovering whether or not a puppy has formed immunity after a vaccine is administeredFinding out if your dog’s immunity to any of those three viruses has “worn off,” and that he’s thus in need of what we call a “booster shot”I’ve long championed titer testing for the first two purposes, and having such a test available right in the veterinarian’s office, with results in as few as 21 minutes, is going to be great.
It’s the third use that I have a problem with, even though I think it’s the one that’s going to excite most pet owners and a lot of veterinarians.
However much we might like to believe we can run in and check the “gas guage” of our dog’s immunity and “top off” his antibody levels with a “booster shot” if necessary — and however much our veterinarians might like to make such a service part of our pet’s annual wellness checks — that is just not how the immune system works.
First, there no evidence that immunity to those three viruses, once formed, wears off during the dog’s lifetime. Virtually all adults dogs who were properly vaccinated as puppies retain immunity to CPV, CDV and CAV-2 lifelong. Outbreaks of parvo and distemper (canine infectious hepatitis caused by CAV-2 is very rare) happen in puppies and improperly vaccinated young dogs, not adult and geriatric populations.
Additionally, immunity to those three viruses is a process, not a substance that can be directly counted and measured.
In the case of CAV-2, CDV or CPV, cells known as “memory cells” are formed when the dog is infected with, or vaccinated for, those viruses. If, later in life, the dog is exposed to the virus again, memory cells will “recognize” the virus and rapidly produce large amounts of antibodies to fight it.
This process happens whether or not there are circulating antibodies in the bloodstream at the time. (Tizard, Ian R., Veterinary Immunology: An Introduction, 6th Ed, Saunders 2000.)
It’s perfectly appropriate and very helpful to check for circulating antibodies shortly (around 2 weeks) after giving a puppy a vaccination, because at that time, their absence will strongly suggest the formation of immunity failed.
This can happen when maternal antibodies interfere with the puppy’s own immune response to the virus. Initial immunization can also fail to take place in a dog of any age if the vaccine is improperly stored or administered, or is somehow damaged, misformulated, or inactivated. Using a test like this after any vaccination is a way to know for sure that immunization took place.
It also makes sense to test a dog of unknown vaccination history, because if he does have circulating antibodies to the viruses, you’ll know that he doesn’t need to be vaccinated for them. This can help rescue groups, shelters, and adopters of stray or rescued dogs avoid giving unnecessary vaccinations, thus sparing the dog the risk of their side effects.
Sure, if the dog doesn’t have antibodies he might be immune anyway, but it’s perfectly rational to err on the side of disease prevention and administer the vaccination.
Unfortunately, that third purpose, the one that has the least scientific support, is being pushed by the manufacturer in this little video they made about the test:
Yes, even inappropriate use of a test like this will help avoid a lot of unnecessary vaccinations. And it will help veterinarians pay their bills, which I’m all in favor of. Some of my best friends are veterinarians, after all.
But there’s still no evidence that dogs who were ever immune to any of those three viruses need either antibody level testing or re-immunization, and unless somebody finds some, I’d recommend sticking to the first two uses for this and any other titer test on the market.
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