I’ve been holding off writing about this, hoping for more details, but my inbox has been flooded with questions about it so I figured I’d get the ball rolling. There’s been a bit of a media frenzy about an apparent outbreak of severe disease in dogs in northern Michigan.

What do we know?

  • Not much.  There have been various social media and news reports about an unknown disease or a “new parvovirus” outbreak in dogs in the area. Reports mention “dozens” of dogs affected, most less than 2 years of age, mainly with vomiting and diarrhea.
  • Concerns about a new strain of canine parvovirus are circulating on social media, but some reports have indicated that while parvo is suspected, test results have been negative. I suspect that’s incorrect, or that there are some nuances to the situation that haven’t been conveyed.

On Monday, Michigan’s state veterinarian’s office issued an update:

“We are still in the early stages of this investigation, but some of the first samples submitted to the Michigan State University Veterinary Diagnostic Laboratory were positive for canine parvovirus. However, there are more results pending and more to be learned,” State Veterinarian Nora Wineland, DVM. “When MDARD first learned of these cases in northern Michigan, we immediately reached out to the veterinarians and animal shelters involved and began our response efforts. Protecting animal and public health is one of the department’s key pillars, but it is a team effort. Dog owners need to ensure their pet is up to date on routine vaccinations as it’s the first step in keeping your pet healthy.”

While light on details, the statement highlights that parvovirus is a leading candidate for the cause at this time. The number of dogs that were positive and the number that were tested area important to put those results into context. Social media reports talk about large numbers of dogs, but that’s not really reliable since cases can quickly be blown out of proportion.  Dogs with any random / routine illness can lumped into case counts without a good case definition and proper data collection, so it’s hard to know the scope of the issue at this time.

What could this be?

A new virus?

  • Probably not. Most outbreaks are caused by the usual suspects. I never discount the possibility of something new, but we start by looking for common things.

An outbreak caused by a new strain of parvovirus?

  • The big concern is about a new strain of parvo that current vaccines don’t protect against. I’d say this is unlikely. Outbreaks caused by “new” strains of parvovirus get talked about frequently but ultimately, they’re usually caused by well-established strains.
  • The “new strain” fears often come up when disease occurs in vaccinated dogs, but most parvo cases in vaccinated dogs aren’t caused by a new strain. Vaccines may not always work in young dogs because antibodies from their mother are still present and can interfere with the vaccine. That’s why we (should) vaccinate dogs at frequently intervals until they’re 16-20 weeks of age. We start early in the hope that they will respond to an early vaccine, then keep vaccinating until an age that we’re confident they will respond.
  • Disease in younger vaccinated dogs can also occur because the vaccine didn’t get a chance to work. We also see issues that are likely due to use of dodgy vaccines or vaccine handling, like when dogs are vaccinated by owners or breeders that get their vaccines from questionable sources, or when cold chain might not have been properly maintained.
  • Disease in vaccinated dogs doesn’t necessarily mean this is a new virus, or a new strain of a common virus, but it’s a consideration, for sure. Disease in older, properly vaccinated dogs would cause me more concern.

An outbreak of our typical canine parvovirus?

  • This is probably the most likely explanation, or at least the one to rule out first. That will require confirmation that parvovirus is actually the cause in most cases, and investigation of the vaccination status of those dogs.
  • Sequencing of parvovirus from affected dogs would ideally be done to see if it’s a different strain.

A social media frenzy?

  • We always have to step back and figure out what we know versus what people are talking about.
  • Not uncommonly, I get questions about an outbreak of X disease and ultimately nothing unique is happening.  Sometimes, a few routine cases get blown out of proportion online.  Sometimes, we hear more about cases that occur routinely in the background, just because people start talking about them.
  • Reports of a large number of sick dogs could truly be an abnormally large number of sick dogs, or it could be the typical number of dogs that are sick but that no one usually talks about. This could also be a situation where there is a small outbreak of parvo in dogs in one area, but lots of dogs with unrelated GI disease are getting lumped in with them, which confuses the issue.

How can dog owners protect their dogs? Especially if they live in or are traveling to Michigan.

It’s mainly common-sense measures and the same things I’d recommend for any area at any time:

  • Make sure your dog is probably vaccinated against parvovirus (and other vaccine-preventable diseases)
  • Keep your dog away from dogs that might be sick
  • Limit contact with other dogs, especially large numbers of dogs and transient populations of dogs that are unfamiliar to you and of unknown disease / vaccination status.

As I mentioned, we typically recommend vaccinating puppies for parvovirus every 4 weeks until 16-20 weeks of age. In shelters, the recommendation is often every 2 weeks because of the increased risk. We have confidence that a vaccine given at 16+ weeks of age will be effective in the vast majority of dogs. At that point, it’s a bit case-by-case. Dogs might get one more dose 2-4 weeks later, especially if they are at higher risk of exposure (e.g. lots of parvo in the area, lots of contact with other dogs and dogs of unknown health status) or we might stop the initial series at that point.  Dogs then get a booster 1 year later, then go on an every-3-year schedule.  The key is getting things started off right.  Proper vaccination of puppies is key to preventing this potentially devastating disease.