‘Mysterious’ Canine Illness: What Dog Owners Should Know

ARIELLE DUHAIME-ROSS: This is Science Friday. I’m Arielle Duhaime-Ross.

If you have a dog, it’s likely that over the past few months you’ve been hearing about a mysterious canine respiratory illness. It’s easy to get a little scared. Some dogs are coming down with severe illness, which can last a long time and doesn’t respond to treatment. These reports have come in from across the country. And in some cases, dogs have died.

In the age of the internet, it’s hard to just how widespread this actually is and how it compares to something more familiar like kennel cough.

Joining me now to help break down these questions is my guest. Dr. Deborah Silverstein is a professor of Critical Care Medicine at the University of Pennsylvania School of Veterinary Medicine, in Philadelphia, Pennsylvania. Thanks for joining me.

DEBORAH SILVERSTEIN: Thank you so much for having me. It’s a pleasure to be here.

ARIELLE DUHAIME-ROSS: Yeah, it’s a pleasure to have you. So just so we’re clear on what we’re talking about here, what exactly are the symptoms of this illness?

DEBORAH SILVERSTEIN: Well, the illness that you are likely referring to, which has recently been dubbed the mysterious dog illness, is something that we’ve actually been seeing for many years and more commonly referred to it as the Canine Infectious Respiratory Disease Complex, or CIRDC, as an abbreviation.

And it’s a very close relative of what you previously mentioned to be kennel cough except we now know that kennel cough is really more than just one bug or one infection, but rather it’s several different potential organisms that can affect dogs’ respiratory tracts and lead to the common signs of coughing and possibly nasal discharge and eye discharge, and sometimes make them even feel sick and not want to eat or play with their normal energy levels, and in rare cases can lead to pneumonia and even life-threatening illness.

What we’ve been seeing in the past couple of years are perhaps some more severe bacteria or viruses that are affecting dogs, not necessarily different organisms from what we’ve previously seen, but perhaps mutated organisms or even dogs that have a very naive immune system and just haven’t been exposed to other dogs the way that they did perhaps before the pandemic. And we even are seeing a decrease in vaccination levels from before the pandemic because it has been harder to get in to veterinarians to get the vaccines that animals need.

So there’s probably several factors as to why we have been seeing more dogs coughing and having respiratory disease. But at this time, we don’t know of a mysterious illness, but rather probably something that we’ve dealt with before that has crept up again. And intermittently, we see more cases of common organisms.

ARIELLE DUHAIME-ROSS: I see. So we’re probably not talking about one single thing. It’s probably a bunch of illnesses, at least some of which are already familiar to us.

DEBORAH SILVERSTEIN: Yes, that’s correct. And I think in human medicine, we often see the same types of problems, where we may get a little cold that’s probably viral in nature. We don’t necessarily run to the doctor when we first feel sick. And then, if we don’t get better or we get better and then we suddenly feel worse again, we may seek medical advice and see whether there’s a secondary infection, like a bacterial infection, that’s led to a new problem or one on top of the original problem like a sinus infection or perhaps a lung infection.

And the same really holds for dogs, where many of them get viral infections that may or may not cause severe illness. But if they get more than one viral infection, or they get a bacterial infection such as the classic kennel cough and subsequently get another infection on top of that, they may become sicker than we would typically expect with just a single-organism infection.

And so it’s important that, as dog owners, we really just keep a close eye on our pets for any persistence of signs or severe signs, where an animal is not eating or wanting to have normal activity levels. Or of course, if they appear to be in respiratory distress, where they can’t seem to catch their breath, their gums or their tongue might appear slightly lavender or bluish tinged, those are indications that we need to bring our animal to the veterinarian or at least call the veterinarian and get advice as to what the best next course of action might be.

ARIELLE DUHAIME-ROSS: OK. I feel like some of this might be a little surprising to some of our listeners because there really has been this narrative around a mysterious new illness, something that we’ve never seen before. And correct me if I’m wrong here, but from what I understand, there does seem to be something that’s novel in some cases.

DEBORAH SILVERSTEIN: I think that holds for all of time. We are constantly seeing infections that are the same viruses or bacteria, but perhaps are a more severe form, just like with COVID, where there’s different strains of the virus, some of which cause a mild cold or no symptoms, but others that may cause life-threatening abnormalities.

And so I do believe that many of the organisms that we’ve been seeing are the same ones that we have seen in previous years. I can’t say with certainty that there is not a new organism– and many laboratories have been working to try and determine if there’s anything to worry about– but it’s quite common for dogs to get colds. Just like for our children that go to daycare to get colds, if a dog is exposed to another dog that may have recently or currently had an upper respiratory tract infection and they are sniffing each other and perhaps breathing some of the same air, it’s very easy for them to pass infections from one to the other.

And most dogs that have a normal immune system will show very mild signs and then be healthy again. If they are vaccinated, it’s possible they may never show any signs or have very mild infection. But because we have a new population of young dogs that maybe were acquired during the pandemic or didn’t have a lot of exposure to other dogs during the quarantine period, and many of whom are also not vaccinated, we may have a bit of a perfect storm, where it’s similar to the child that’s never seen another child and suddenly goes to first grade. More than likely, they will get some infections when they’re put in close proximity with other children that likely are passing along little upper respiratory tract infections.

And it’s the same with dogs that maybe are for the first time going to boarding kennels or doggy daycare or groomers or even classes, where they can get better behavior from their isolation during the pandemic. And so they’re getting exposed to probably some of the same organisms we’ve seen in the past, but they have a very naive immune system. And we know that many dogs with flat faces are popular right now and they tend to have a harder time clearing these infections because their respiratory tract is not normal compared to dogs with longer noses.

ARIELLE DUHAIME-ROSS: Oh, really. So dogs like pugs, for instance, would be more at risk?

DEBORAH SILVERSTEIN: Yes. Yes, exactly. So pugs, bulldogs– the infamous French bulldog that is so popular right now. We know that their immune systems are not always as strong or robust as other types of breeds. So when they get a mild upper respiratory tract infection, they may or may not get over it as quickly as other breeds of dogs.

So we are a little bit more cautious when presented with what we call brachycephalic, but more commonly known as smooshed face or flat faced, types of dogs with an upper respiratory tract infection because we know that they are more likely to have issues, where they may not be able to breathe or they may develop pneumonia due to altered clearance mechanisms in their lungs.

ARIELLE DUHAIME-ROSS: So what you’re describing is sort of a complex series of circumstances surrounding these illnesses. And I’m wondering, how does the mortality rate right now when it comes to these respiratory illnesses compare to before the pandemic, for instance? Should we actually be more worried than we were before as dog owners? I personally have two dogs. How worried should I be right now?

DEBORAH SILVERSTEIN: Well, that’s a great question. And I think there’s really not reason to be worried. I do think that it’s important to stay updated on information in your area regarding any uptick in respiratory infections in dogs. You might want to ask your daycare, your groomer, anywhere that your dog frequents, especially if they’re in close quarters with other dogs. It’s important to be aware if there’s an outbreak of upper respiratory tract infection.

Similarly, it’s important to talk to your veterinarian about what vaccines are most appropriate for your dog based on their lifestyle and to always stay vigilant with regards to what other animals your dog encounters, even at parks or on walks and the neighborhood. If they have any evidence of discharge from their nose or their eyes or they’re coughing, it’s very easy for your dog, even in a one- or two-minute encounter, to get exposed to some of these different viruses and bacteria.

So for pet owners, I think being cautious is appropriate. I don’t think there’s need for extreme worry or not taking your dog to socialize, but maybe to limit their interactions with other dogs if there’s a known uptick in infections in your area and to make sure that anywhere you take your dog is a responsible type of business, where they take really serious precautions to identify animals that might have illness and to prevent any spread of illness in their facilities.

ARIELLE DUHAIME-ROSS: All right. Well, it sounds like the takeaway is don’t panic.

DEBORAH SILVERSTEIN: Yes.

ARIELLE DUHAIME-ROSS: And talk to the people who interact with your dog. Thank you so much. That’s all the time we have for now.

Dr. Deborah Silverstein is a professor of Critical Care Medicine at the University of Pennsylvania School of Veterinary Medicine, in Philadelphia, Pennsylvania. Thanks for joining me.

DEBORAH SILVERSTEIN: Thank you for having me.

ARIELLE DUHAIME-ROSS: So this quote, unquote, mysterious illness might not actually be just one thing, but there does appear to be something new involved here at least in some cases. And researchers out of New Hampshire are determined to figure that out.

Joining me now to talk about what we’ve learned is my next guest. Dr. David Needle is a pathologist at the New Hampshire Veterinary Diagnostics Laboratory and a clinical associate professor at the University of New Hampshire, in Durham.

Welcome. Thanks for joining me.

DAVID NEEDLE: Thank you for having me.

ARIELLE DUHAIME-ROSS: So this really is something we haven’t seen before.

DAVID NEEDLE: That’s what it looks like. And one of the really cool pieces of data is we have a biobank, or a biological repository, where we freeze back specimens from carcasses and other samples that come through the lab. And we save them for diagnostics, but also for potential investigations.

And so we have tested samples from 2018, from 15 dogs, and did not find evidence of this bacteria. And in addition, if someone publishes a paper, looking at the respiratory microbiome or any type of other sequencing-based study, they publish all of their data on online repositories. And we have searched back through five other studies and found no evidence of this bacteria.

ARIELLE DUHAIME-ROSS: OK. So you’re definitely starting to learn about this thing. You’ve been analyzing samples from across the country. Are you seeing the same potential pathogen in New Hampshire as you’re seeing in Oregon?

DAVID NEEDLE: Yeah. Funny enough, New Hampshire and Oregon, yeah. Colorado sent us some great samples. And I talked to some really awesome clinicians there. And out of the 31 samples we tested from Colorado, none had genetic material from this bacteria.

ARIELLE DUHAIME-ROSS: Oh.

DAVID NEEDLE: Which was surprising.

ARIELLE DUHAIME-ROSS: Oh, that’s interesting. Yeah.

DAVID NEEDLE: Yeah. So in Southern California, contemporaneous to the pops in Colorado and Rhode Island, they had an outbreak of respiratory disease that ended up being a known pathogen, Streptococcus equi, subspecies zooepidemicus– or people just call it Strep zooep sometimes because it’s real cool.

ARIELLE DUHAIME-ROSS: So cool.

DAVID NEEDLE: Yeah. I mean, there’s nothing cooler than talking about microbes.

ARIELLE DUHAIME-ROSS: True.

DAVID NEEDLE: So that’s a pathogen that emerged a decade or so ago to be an impactful pathogen in dogs in group housing situations. And so that’s one of the things that’s an important part of what’s going on is we have to, in each case, do the normal investigation first.

ARIELLE DUHAIME-ROSS: Right. Well, what I’m getting from you is that all of these different reports of outbreaks of this one mysterious illness– what I’m getting from you is that, while in New Hampshire and Oregon that was in fact the case, it’s not the case everywhere. In some places, it was an outbreak of something that we had previously identified and knew about. So why is it so hard to break down and identify what this new pathogen is?

DAVID NEEDLE: So DNA has a four base pairs, A, T, G, and C. And A and T pair together and G and C pair together. So this bacteria has a very AT-rich genome. And the most commonly used sequencing technology is Illumina based. So NovoSeq or MiSeq/PiSeq And in the probes that it uses to generate the sequencing, it’s not biased as far as it’s sequencing everything with the probes that it has.

If you were to send through a swab of your nose or my nose, it’s going to be 99% us and 1% our microbiome and some pathogens. And if you’re going to send through you or me, our normal GC content, which is a lot higher than this bacteria, will outcompete the bacteria. It won’t be able to be picked up. So that’s one of the reasons.

ARIELLE DUHAIME-ROSS: Meaning that you are getting a lot of dog in your samples.

DAVID NEEDLE: Right. And that even taking out the dog, we’re going to have normal dog respiratory bacteria, which have quote, more normal GC content, which will outcompete this.

And so there’s other laboratory methods we’re going to use to more likely select for this type of pathogen. And then it’s not an easily cultured– it won’t come up on a standard bacterial culture. And so we’re going to be working with an expert in culturing fastidious small bacteria. And if we can culture it, that would be a really huge step.

ARIELLE DUHAIME-ROSS: So it really is about getting that dog DNA out of the way and sifting through the rest of what’s part of the respiratory microbiome to really identify and drill down and identify this one potential pathogen and really identify it.

DAVID NEEDLE: Right. And so it’s an interesting combination of the bioinformatics and data analysis wizards at the Genome Center, and also then myself and my colleagues at the Diagnostic Lab, looking through the data and being like, well, this is a pathogen. This is nothing. This is something we see when we culture all the time. It’s just background.

So it’s an interesting combination of the most fancy sequencing and informatics pipelines and then people getting their eyeballs on it and talking and thinking.

[LAUGHTER]

ARIELLE DUHAIME-ROSS: Yeah. What you’re describing is oddly old school even though you’re using the most advanced machines that we have to do this kind of work. It’s sort of wild.

DAVID NEEDLE: Right. Thankfully, AI hasn’t gotten rid of me yet.

ARIELLE DUHAIME-ROSS: Right. Well, there you go. One example where we still need human eyeballs and a brain.

That’s all the time we have for now. I’d like to thank my guest. Dr. David Needle is a pathology section chief at the New Hampshire Veterinary Diagnostic Laboratory and a clinical associate professor at the University of New Hampshire, in Durham.

DAVID NEEDLE: Thank you.

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