Lately, there have been quite a few news reports about canine parvovirus in London, Ontario. Overall the report have been pretty balanced, highlighting the fact that parvo is causing problems but not overplaying the issue (which happens all too often). Some reports have said there’s an “outbreak” of parvo in an area.

Sometimes a situation like this may be a true outbreak, but most often, it’s a small cluster among the baseline of endemic disease, or it’s just an “outbreak of discussion,” not disease. My guess is that the issue here is the typical small cluster of cases in a group of inadequately vaccinated dogs that’s gotten some extra attention and media chatter, but that the overall parvo rate and risk in the city is pretty much unchanged. Unfortunately (and as usual), we don’t really know for sure, since data are sparse, anecdotes can be misleading, and we don’t have any formal surveillance for parvo in dogs.

Canine parvovirus is an endemic virus pretty much everywhere on the planet where there are dogs. When it first emerged, it was devastating, causing widespread illness and death. Now, it’s largely controlled in areas where there’s good vaccine coverage in the canine population, but cases still occur because of incomplete vaccine coverage and infection of puppies before they can develop protection from their vaccines.

Vaccination is undeniably the cornerstone of parvovirus control where it’s available. We have really effective and safe vaccines for this very serious disease, that’s caused by a virus that’s highly transmissible and hard to avoid. In one article, a veterinarian was quoted as saying parvo vaccination for dogs is “non-negotiable” in her practice, and that’s a fair position to take.

Our parvo vaccines are incredibly effective. It’s exceedingly rare to see parvovirus in a properly vaccinated dog. Almost invariably, if a “vaccinated” dog gets parvo, it’s a dog that didn’t get a full/proper vaccine course.

Most of the parovirus vaccines currently available on the market are modified live virus (MLV) vaccines which are very effective, and can produce robust immunity with a single dose. However, vaccine response in puppies can be unpredictable. If their mother was vaccinated against (or previously infected with) parvo, she will pass antibodies on to her puppies. Those antibodies hang around for a while, providing some protection but also interfering with vaccine response. That’s why we typically vaccinate puppies at 8, 12 and 16 weeks of age – not because they need multiple doses or a specifically timed series, but rather because we want to start young to try to get the puppy protected ASAP in case those maternal antibodies are starting to disappear, and continue to an age where we’re pretty confident that the puppy will produce its own active immune response to the vaccine.

I want to get at least one dose of parvo vaccine into any puppy at 16 weeks of age or more. An extra booster at 20 weeks of age is a bit of an insurance policy – it’s probably not needed if the puppy got a dose at 16 weeks, but it provides an extra buffer in case the puppy is one of those rare cases that didn’t response to the previous dose because of lingering maternal antibodies.

After that 16 or 20 week dose, we give the dogs another dose in 6-12 months of age. With that, we have given 2 doses that we are quite confident will stimulate an active response and provide immunity, and given over a relatively long time frame (which typically produces a better immune response than a condensed series of vaccines). That should give the dog very solid immunity for at least 3 years (and probably more, but we don’t know how much more in any given dog).

If an adult dog hasn’t been vaccinated before (or it’s vaccine status is unknown), it should respond nicely to a single dose of parvo vaccine. A second can be given a month later, but it’s probably unnecessary. An additional dose 6-12 month later will then establish nice long-lasting immunity.

So, if you have a puppy:

• Make sure you talk to your veterinarian about vaccinations ASAP. Sadly we see cases of parvo in young puppies where the owner just didn’t get around to getting the dog vaccinated as early as possible (life’s busy and it’s easy to forget…). Parvo can then be fatal, and/or can be very expensive to treat (particularly relative to the cost of a vaccine appointment…).

• If your puppy has gotten a parvo vaccine, and it’s less than 16 weeks of age, one is NOT enough. We need to makes sure the dog gets that dose at 16 weeks or more. Most “of ‘”vaccine failures” I see are dogs that got their last dose at 12 weeks. That’s not a vaccine failure in my mind, that’s a dog that didn’t get vaccinated properly. Since rabies vaccination can be done (and is ideally done) at 12 weeks of age, some people forget or are less motivated to get the 16 week parvo vaccine, but critical to ensure that gets done. It can be a life-or-death decision for some dogs.

As with most of these “outbreaks,” things will likely die down in London ON, likely from a combination of improved vaccination, the infection burning through the high risk group, and waning attention and discussion. That’s the usual routine. However, we will see similar incidents elsewhere. Parvo will always be a risk wherever there are dogs, so we need to maintain vigilance and vaccine coverage.

Vaccine hesitancy is a challenge in veterinary medicine, just like human medicine. So is complacency. When vaccines work, people don’t see the devastating disease, and they forget why those routine vaccines are so important.