Here’s a question I get a lot that I’ve posted about before:

I am immunocompromised, is it safe for me for my pet to get a modified live vaccine?


A client came in and said their physician told them their pet should only receive killed vaccines.

Here is a little background first:  Killed vaccines contain dead (inactived) viruses or bacteria, or bits of them. There’s nothing “alive” in the vaccine that can replicate, but the immune system can still respond to the fragments of the target pathogen. Modified live vaccines (MLVs) use strains of a virus or bacterium that have been weakened so they don’t cause disease, but it’s still an active (“live”) microbe. In general, modified live vaccines are ideal since they stimulate an immune response that’s stronger and more comparable to what happens when the body encounters the normal (“wild type”) equivalent of the bug in the vaccine.

However, there can be risks with MLVs to people (and sometimes animals) with compromised immune systems, since even those weakened bacteria or viruses might cause disease in rare circumstances.

The Canadian Immunization Guide states “In general, people who are severely immunocompromised or in whom immune status is uncertain should not receive live vaccines because of the risk of disease caused by the vaccine strains. In less severely immunocompromised people, the benefits of vaccination with routinely recommended live vaccines may outweigh risks.”  These guidelines are focused on vaccines against human diseases and the emphasis on people with severely compromised immune systems is important to note.  Sometimes, this concern washes down to include exposure to modified live vaccines for animals.

When thinking about the risk, the first thing to consider is whether the original wild-type bug that was modified (or killed and chopped up) to make the vaccine is able to infect people. If the normal bug can’t infect a person, there’s no reason to think that a weakened strain of the same bug would pose any risk. That eliminates concern about almost all of the animal vaccines we use.

The concern about MLVs for animals usually crops up in relation to Bordetella bronchiseptica. This bacterium is one of the many causes of “kennel cough,” and there are both oral and intranasal vaccines for dogs that use a modified live strain of the bacterium. For B. bronchiseptica, these MLVs offer much better protection for the dog than the injectable killed vaccines. Bordetella bronchiseptica can cause infections in people, but it’s very rare. So, the modified strains used in these vaccines should be even less of a risk to people – but very low doesn’t mean zero.

I’m only aware of a couple of reports of human infections from B. bronchiseptica vaccine. One is a person that was squirted in the eye with the vaccine. The other was a person who had had a kidney-pancreas transplant (and would therefore be very immunosuppressed) and was suspected to have been infected via her recently vaccinated dog.

Overall, the risk posed to people by these vaccines is very low.  The main risk would be from being exposed to a large dose, such as being squirted in the face when the dog is vaccinated, or having a vaccinated dog immediately sneeze on or lick the face of the high-risk person. These types of exposure are avoidable using simple measures such as keeping high-risk individuals out of the room when vaccinating (or at least keeping them away from the animal’s face), avoiding contact with the nose and mouth of the dog after vaccination (something that a high-risk person should do anyway), and using good routine hand hygiene  (another thing a high-risk person should do anyway).

Additionally, we need to consider the risk from the vaccine strain versus all the other bacteria that are present in every dog.

  • If I had just vaccinated a dog with a modified live Bordetella vaccine and you asked me to rank the microbes in the dog’s nose/mouth that could potentially harm someone, the vaccine strain wouldn’t even crack my top 10 list. That’s not to completely dismiss concerns about live vaccines, but it helps put them in perspective.

And one more thought to consider…  what are the benefits to that same high-risk person of vaccinating the dog?

  • If a dog gets Bordetella infection, there’s some (very slight) risk of infection of an immunocompromised owner from that bacterium. Additionally, a coughing dog aerosolizes more bacteria from its respiratory tract, maybe increasing risk of exposure to that bacterium and other more concerning bacteria in the dog’s respiratory tract. Maybe more importantly, if the dog gets antibiotics for kennel cough (not usually needed but they tend to be overused), then the biggest risk is probably the emergence of various antimicrobial-resistant bacteria in the dog, with the potential for human exposure.

So, most of the MLVs we used in dogs and cats pose no risk to people. Bordetella vaccination poses such a low risk that I think the overall benefits clearly outweigh the risks. Every high risk person should have a detailed talk with their physician (or ideally an infectious disease physician) that is well versed in zoonotic diseases to make a plan for reducing the risks associated with routine pet contact. Avoiding modified live vaccines in the pets is unlikely to be a part of that.

I’ve gotten behind on writing so I’ll start back with a quick post. The World Small Animal Veterinary Association (WSAVA) has released an advisory document about the new coronavirus (the cause of the newly named disease COVID-19).

On the animal front, it’s still an ongoing battle to balance awareness (considering potential zoonotic sources and what to do with exposed animals) and over-reaction (resulting in paranoia about contact with any animals). We still have no evidence that this virus affects domestic animals, but since we also still have no real evidence that it doesn’t, it’s best to continue to take reasonable precautions to reduce the risk of exposure of animals to infected people, and to properly manage pets of people who are infected. It’s not necessarily complicated, and it hopefully won’t be necessary, but it’s always better to practice prevention than damage control.

On the prevention front, my dog Merlin had fake coronavirus for the day (just like he had fake Ebola a few years ago) to practice our containment practices. He escaped unscathed, and Merlin made the front page of the Toronto Star in the process.

I haven’t written much here about the 2019 novel coronavirus from China lately. In part, that’s because I’ve spent a lot of my time writing or reviewing documents for various groups on the topic. A common challenge I face with zoonotic diseases is the message. On one hand (or for some groups), I’m trying to raise awareness, to makes sure animal aspects are properly addressed. On the other, I’m trying to make sure people don’t go over the top and become paranoid of animals of one species or another. It can be a battle sometimes, because the line between awareness and paranoia is pretty short.

Another issue is lack of resources, expertise, confidence or willingness to consider options when it comes to managing the potential zoonotic risks, particularly with a novel virus strain like this one.

What’s the easiest (or most obvious) way to eliminate a zoonotic disease concern?

  • Eliminate the animal(s).

We’ve seen this lots of times in the past, where fear, lack education or lack of desire lead to euthanasia of pets or other animals that is completely unwarranted.  Unfortunately we’re seeing it again with the 2019 novel coronavirus.

What are we talking about, in terms of increasing awareness?

The big thing is we don’t know which animals can be infected. Too often, the default is to say “animals can’t be infected” until it changes to “oops… I guess they can.” Major agencies have said “we have no evidence that domestic animals can be infected.” That’s true. It’s also true that we have no evidence that they can’t. Some of those groups’ messages have changed over the past few days to at least say that infected people should stay away from animals, as a precaution. That’s a great start.

The prudent approach is to assume animals can be involved in coronavirus transmission until we’re sure they can’t. SARS provides a perfect example of why we need to be careful about this issue. We know now that cats and ferrets are susceptible to SARS, which is a relative of the current novel coronavirus. We also know that an SARS-infected cat can infect another cat, and the same goes for ferrets. So, it’s reasonable to assume that cats, dogs, ferrets and/or other animals could be infected by other related coronaviruses too.

What does that mean we should do?

Pay attention but not panic. My general line is that we need to treat animals like people. If someone is infected, the response would include tracing that person’s contacts. Typically, that means human contacts. For me, that means anything with a pulse. If someone is infected and their spouse is being quarantined, the same quarantine should apply to their pets.

What are we talking about in terms of decreasing paranoia?

Thinking about the potential role of animals is great.  Thinking all cats are going to kill us is not. There are simple approaches to identify exposed animals and to properly manage them. Household quarantine of pets can be done. Sometimes it’s challenging (especially with dogs) but it’s doable in many households, and a few facilities (like ours) are equipped to handle quarantine of pets. My dog, Merlin, had “pretend-Ebola virus” for the day a few years ago when we were testing our Ebola containment procedures. He’s going to have “pretend-coronavirus” on Friday as we do a practice run for this virus.

Is there actually a problem?

Probably. We’re getting lots of reports from China and elsewhere about dogs being killed in large numbers. Finding out why is critical.

Is it because people are afraid they’ll get infected by their dog?

  • That’s an easy educational piece. If I don’t have coronavirus and my dog stays in the house, he’s not getting exposed. If I keep my dog away from other dogs or people, the only way he’s getting exposed is from me.

Is it because they don’t think they can care for their dog if they can’t leave the house?

  • That’s another, but different, educational piece. We need to educate people about how to manage a dog inside a house for a couple weeks.

Is it because they can’t get food for their dog, since their movements are restricted?

  • That leads to a need to figure out a support system, just like a person would need to get food/groceries for themselves.

Knowledge vacuums lead to fear. Fear leads to knee jerk decisions, and those often lead to bad outcomes. It’s a scary situation in areas where this virus is active and fear-based responses are understandable, but still unfortunate. However, we can do a better job managing the virus and the fear. In areas where this virus has not yet established itself, it comes down to:

  • Ensuring animal contacts of human cases are queried.
  • Ensuring exposed animals are quarantined.
  • Using good old fashioned infection control, like hand washing.
  • Keeping the fear at bay and applying logic to the problem.

A long post (rant), but that’s a quick summary of what I’ve been dealing with.

I’ll probably post some “Merlin’s day with coronavirus” pictures later this week.

While the whole story hasn’t been sorted out, it seems pretty clear that one or more animal species at the Wuhan Seafood Market (which sold much more than just aquatic animals and their products) was the source of the novel coronavirus.  Just like SARS.

Once again, this has raised concerns about markets where diverse live animal species are sold to large crowds. In a few interviews lately I’ve been asked about the role of wildlife markets like this in disease. There’s not a good answer and it’s a hard question to answer, because of the lack of information and also some important cultural contexts that have to be considered.

One reporter asked whether illegal wildlife trade is a concern. Really, “legal” or “illegal” probably doesn’t change the risks too much. Legal or illegal isn’t necessarily based on infectious disease risk, although illegal markets might mean less overall scrutiny, which could make things a bit more hazardous.

One question is, “Do wildlife markets pose a risk?” 

The answer is clearly “yes.”

Why?  These markets bring lots of animals and lots of people together. Wildlife in particular bridge the gap between “the wild” and the rest of “us.” That’s a concern because there are many undiscovered infectious diseases lurking in the wild.  As we encroach more into previously wild areas and bring animals from those areas to areas where people live and work, we increase the risk of being exposed to something nasty that’s been hiding out peacefully in the wild animal population.

The harder question is, “What should be done about wildlife markets?” 

The most logical answer, one that is easy to say from a distance, is “don’t allow them.” That would be ideal, as it would reduce contact between large numbers of people and large numbers of animals, as well as contact between large numbers of different animal species. There are also animal welfare and conservation benefits. Yet, I’m not in a position to say ‘”close them down” because I don’t know the social, cultural and food access issues, which can be different in each case. I suspect these markets could be closed down with complaints but no major problems, but I’m old enough to know that first glances from a distance aren’t always right. We’ll see how things progress with the ban of the wild animal trade that was put in place across China on Sunday, in terms of whether it will be sustained, and whether it will actually stop the trade or push it underground…

Like most zoonotic disease issues, this is a complex area that will likely defy a simple solution.

It was a bit of a slog but we’ve posted the updated 2020 edition Infection Prevention and Control Best Practices for Small Animal Veterinary Clinics. In addition to updated information, the new version has many new and expanded subjects, and provides a comprehensive guide to infection control for veterinary hospitals.

Click here to download the guidelines (open access).

There’s also a voluntary survey linked to it for any veterinary staff members who want to provide their thoughts about guidelines. It will help us assess what we have and what we need to do for future revisions.

The situation with this novel coronavirus in China is rapidly evolving, with more aggressive control measures locally and lots of planning elsewhere. Recently, snakes were suggested as the origin of this virus, which was surprising and contrary to the assumption that this would be traced back to bats.

Information (as well as speculation) now seems to be flowing more rapidly with this outbreak, and the snake hypothesis has been challenged by many since it came out. Click here for a more detailed discussion of the links between this novel coronavirus, bats and snakes (or not), for those who are interested.

I’m sure we’ll see much more genetic analysis of this virus by many different groups, but I suspect it will keep coming back to bats as the source. How it made it to humans will still be a big question, since it’s quite likely there was a different species that bridged bats and humans (as was the case with raccoon dogs and civets with SARS).

Norovirus infections suck. I know from personal experience.

Sometimes incorrectly referred to as the stomach flu (since it has nothing to do with influenza), norovirus infections in most otherwise healthy people tend to be fairly short-lived, but they still make you feel miserable (to say the least).

Previous studies have suggested that dogs can sometimes be infected with noroviruses, but data have been limited. So, my general recommendation has been to just try to avoid puking on your pet. Less dramatic contamination of a pet’s haircoat (e.g. you have norovirus on your hands and you pet the dog/cat, and then someone else pets the same animal) probably also poses some risk of transmission between people, just like inanimate objects that have been touched. However, I haven’t been too concerned about dogs actually getting infected themselves and then infecting people.

A recent paper in Emerging Infectious Diseases (Charoenkul et al. 2020) adds a twist to the situation. It describes an outbreak of gastrointestinal (GI) disease in kids and dogs in a household.

Two young kids got sick first and were diagnosed with norovirus. Shortly thereafter, two dogs were moved from the family’s kennel into the household. Those two dogs, plus 5 of 6 puppies from a litter born in the household developed GI disease a short time after the kids got sick. Norovirus was found in fecal samples from the puppies and adult dogs in the household. Some dogs were positive for three weeks, which makes it more likely that they were truly infected (i.e. the virus was replicating in the dog), rather than the test simply detecting norovirus particles that had been ingested and were just passively moving through the dog’s intestinal tract and came out the other end. No other typical causes of canine diarrhea were identified. That doesn’t guarantee the problem was norovirus, but it makes it more likely.

When they looked at the genetic makeup of norovirus in the two human samples vs the two canine samples, the viruses from the dogs “clustered” with the human viruses, and they were all consistent with the typical human norovirus, not the noroviruses previously reported in dogs (see image below). This all makes it most likely that the human and canine infections were linked, and that people were the source.

Is this a big deal?

  • Probably not. However, it provides more evidence that dogs can sometimes be infected with human norovirus.  Since the virus was detected in the dogs’ feces, it raises the potential that they could then infect people.
  • While it’s not a game-changer, it’s still interesting and shows the importance of basic hygiene (especially handwashing) when you’re sick, remembering that pets can be part of the family microbiologically, as well as socially.

The recent reports of human-to-human transmission of the novel coronavirus that’s been identified in China certainly raise the stakes. While this virus still seems to be less transmissible and less virulent than its relative, the SARS coronavirus, it’s pretty early to have a lot of confidence in that. Lessons seem to have been learned from SARS, but at the start of an outbreak it’s hard to predict too much.

What’s the companion animal spin?

Human infections were first linked to an animal (seafood) market. That’s not surprising, since SARS also started at an animal market, and lots of undiscovered coronaviruses are lurking in different animal species (especially bats). The fact that the outbreak was first linked to an animal market doesn’t mean the animals were the source (because there are also lots of people in markets), but it would make sense.

If that’s the case, it’s a bit optimistic for us to think that this virus would be able to infect only its host species and people.

Looking back at SARS, we know that virus can infect a few different mammals, including cats. When SARS was a problem in Canada, people who were exposed underwent voluntary household quarantine, meaning they were supposed to stay at home and away from family members for a period of time. Yet, nothing was said about pets. I could have been quarantined in my basement, away from my family, but still have had regular contact with my cat, who then could have had contact with the rest of the family (and if he was an indoor-outdoor cat, contact with other cats). Think what would have happened if SARS was able to establish itself in the feral cat population of a city like Toronto. It’s probably not transmissible enough between cats to do that, but we didn’t know that at the time. I remember emailing someone who was dealing with the SARS crisis in Ontario at the time about the pet issue, and the response basically was “Good point. Gotta go.” When dealing with a crisis, something ancillary like that isn’t high on the priority list.  We wrote a commentary about the potential risk of pets in household quarantines related to SARS a little while later that got some attention, but I’m not sure there was much action.

That’s why we need to be proactive. For containment measures for SARS, this new coronavirus or any other new disease, we need to assume that multiple species can be affected until proven otherwise, and we need to act accordingly. That doesn’t necessarily need to be complex. It might just be making sure animal contact questions are asked along with human contact questions, that quarantine protocols consider what to do with exposed animals, and that quarantined individuals are kept away from animals. We developed guidelines for management of pets related to Ebola exposure a few years ago, and it took a lot of time to get it right.

Hopefully we don’t have to worry about it, but it’s better to plan ahead than try to catch up.

I saw a TV commercial yesterday talking about a skin product and how it “protects your microbiome.” Microbiome is a big buzzword now, but do what do we really know?

A lot, and almost nothing.

The microbiome is the vast population of microorganisms (mainly bacteria) that live in a site like the intestinal tract, respiratory tract or on the skin. While we often think about bacteria as causes of disease, they’re also critical for our survival. The overall population of microorganisms (the microbiome) provides many benefits to the host (be it a person or animal), but how it interacts with the body is complex and poorly understood.

I’ve been working on microbiota for quite a few years and I think I understand a fair bit about it, but I also think I understand little about it in the grand scheme of things. People often think it’s this cutting edge new technology (it is) that can tell us a lot about ourselves or our patients (it can) and guide medical decisions (not yet). The problem is, there’s a difference between information and knowledge. If you give me a fecal sample (or sample from any other site), I can tell you lots about what’s in it. I can tell you how that fits on a population level with normal or healthy groups. But, I can’t say much with confidence about that individual.


While we’re getting more and more information about the microbiome in healthy and sick animals and people, we don’t really know what we’re looking at. There’s a wide variety of “normal” microbiomes, not just one. If you take 100 healthy dogs and 100 dogs with inflammatory bowel disease, there will be some clear differences between the overall groups. However, some of the sick dogs will have microbiomes that look just like normal dogs, and some perfectly healthy individuals will have microbiomes that I’d consider completely screwed up.

Also, while we get reams of data, and there are lots of ways to analyse them, we still don’t really know what the most important elements are. Is it the overall richness (number of different bacterial species)? Their diversity? The presence of specific bugs? Ratios of specific bugs or groups?

There are still many other issuses as well. For example, does a single sample tells us the whole story? Do data from one geographic region apply to another? Do we need to account for diet, age and various other factors? Should a healthy vegan’s microbiota, for example, be expected to be the same as a healthy meat eater? How good is testing feces when disease occurs higher up in the intestinal tract?

Lots of questions still need answers.  This isn’t meant to dismiss the importance of the field. Like many other groups, we continue to work to try to figure out the microbiome. However, we need to make sure we stay grounded and remember how little we actually “know”.

You can pay to get your dog’s (or your) microbiome tested, get recommendations about whether it’s “normal,” and sometimes be sold treatments as a result of that interpretation. You can buy products to “protect” your microbiome (without much or any evidence behind them). However, remember that marketing often outpaces evidence.

The microbiome’s a wonderful thing. I can’t wait until we understand it better.

This is a smaller outbreak than the puppy outbreak from the previous post, probably in large part because fewer people have contact with geckos, but… Contact with reptiles such as geckos has been a known risk factor for human salmonellosis for years. That’s a big part of the reason for recommending that high risk people (i.e. those less than 5 years of age, over 65 years of age, pregnant, or immunocompromised) have no contact (direct or indirect) with reptiles.

In this outbreak (Koski et al, Zoonoses and Public Health 2019), Salmonella Fluntern was the cause of infection in 12 people in 4 US states (Oregon, California, Iowa and New York). The median age of those affected was 5 years, with a range from less than 1 to 58 years of age (so much for the “keep young kids away from reptiles” recommendation). No one died, but 3 people (25%) were hospitalized. Most people reported contact with leopard geckos, and the same bacterium was isolated from a gecko owned by one affected person.

No common source of geckos was identified and their bacteria were different enough genetically that a point source isn’t likely. Other gecko- or reptile-associated Salmonella Fluntern isolates were identified in bacterial databases from Europe. So, this suggests that Salmonella Fluntern is a reptile (or even gecko) associated strain, posing a broad risk to reptile/gecko owners.

This report doesn’t change any recommendations, but just shows (again) the issues that are involved. Reptiles shouldn’t be in high risk households. People with reptiles need to use some basic hygiene precautions to reduce their risk of infection. It’s not rocket science, but it’s often neglected.

More information about reducing the risk of infection associated with reptiles can be found in on the Worms & Germs Resources – Pets page.