I got a question about an old post on this topic, so I decided to add a bit of information and re-post it. Not much has changed since it was written in 2018, apart from more reports of people and pets getting sick from raw pet food and raw treats.

Is freeze-dried raw pet food any different than fresh or frozen raw diets, from a microbiological standpoint?

We don’t have much pet food-specific research, but there’s little reason to believe there would be much difference between these types of diets when it comes to the microbes we’re concerned about. When I want to preserve bacteria, I freeze them or freeze-dry them – those are actually the preferred methods for long-term storage of bacteria. Freezing or freeze-drying is a pretty hospitable process and state for most bacteria. Some, such as Campylobacter, don’t tolerate freezing (or especially fresh-thaw cycles) as well as others, so freezing or freeze-drying might have some impact on those specific bugs. For the higher profile pathogens like Salmonella, E. coli and Listeria, it probably doesn’t have much of an effect. I can see there being some reduction in bacterial numbers but probably nothing substantial, and certainly not enough that I’d consider it when deciding whether it’s an appropriate diet for a particular pet and household.

The story is quite different for some parasites. Many parasites and parasite eggs don’t tolerate freezing – that’s why fish for sushi is typically frozen at some point before it is served. Some are hardier than others, though. Toxoplasma, a potentially important foodborne parasite, is susceptible to freezing, but only if the temperature is low enough and the time is long enough (e.g. -12C for 3 days will kill most Toxoplasma cysts.  To put that into context, typical household freezers run around -20C).

So, the take home message is that for of the microbes that we’re worried about with raw meat,  freezing or freeze-drying is NOT a food safety practice. It’s food preservation, not bacterial control.

Another point to add… advertizing around pet diets is variable and sometimes quite dodgy. I just checked two websites selling freeze-dried raw diet. One had good info. The other… well… not so much.  Don’t let company advertizing be your infection control guidance.

More information on raw diets and toxoplamsosis are available on the Worms & Germs Resources – Pets page.

I usually link blog posts to Tweets, rather than re-hash my Twitter musings (weese_scott) on the blog, but two things I posted on Twitter today may be of interest here.

COVID-19 in captive gorillas

Not surprisingly, COVID-19 has been identified in captive gorillas, in this case at the San Diego zoo.  It’s suspected that the gorillas were infected by an asymptomatically infected keeper, despite the intense precautions that have been taken to try to protect the animals since the pandemic began. It’s not at all surprising, since we assumed gorillas (and other non-human primates) that are relatively closely related to humans would be very susceptible to the SARS-CoV-2 virus, just like we are. With COVID-19 running rampant in California, it’s also completely unsurprising to have had an asymptomatically infected keeper at the zoo.

The more interesting aspect might be how the virus was actually transmitted from person to gorilla. Zoos tend to have very strict control measures in place to prevent this from happening (even when there isn’t a global pandemic), and the San Diego Zoo is an excellent facility. Figuring out how this occurred (e.g. inadequate practices, inadequate compliance) will be important to guide control measures at other facilities.

Toxoplasma gondii associated with brain cancer

Toxoplasma gondii is a protozoal parasite that has been linked to lots of issues in people, often with somewhat questionable evidence. Cats are the definitive host of this parasite, for which they get a very bad rap, but most human exposure is from the environment or food.

A recent paper has made some interesting but tenuous links between Toxoplasma infection and glioma, a type of brain cancer. It was interesting research, involving a large prospective study in which they collected blood samples from cancer-free people, and then followed them over time. After 13 years, they looked at the risk of gliomas in those who did or did not have antibodies against T. gondii prior to diagnosis (probably no real reason for picking 13 years… long enough for cancer to develop and it happened to be when they were ready to look at that).

There were some weak associations between one type of Toxoplasma antibody and development of glioma and glioblastoma. The data aren’t too convincing, but there are some similar results from elsewhere, which shows the subject needs more study.

What does this mean for cat owners?

  • Very little. Gliomas are a rare cancer, and while Toxoplasma exposure is quite common, it’s not usually from someone’s pet cat. Toxoplasmosis is a “don’t eat poop” disease, so there are lots of simple, routine things we can do to reduce the risk from pet cats (like not touching cat feces and washing your hands after cleaning the litter box).

More of my comments are posted on Twitter here: https://twitter.com/weese_scott/status/1348707854430167040

We have more information about Toxoplamsa on the Worms & Germs Resources – Pets page.

Here’s the latest version of our pandemic guidance document for Ontario veterinary clinics, produced in collaboration with the OVMA.  Previously entitled “A guide to reopening veterinary medicine in Ontario” it has been retitled “A guide to mitigating the risk of infection in veterinary practices during the COVID-19 pandemic (04-Jan-2021)“.

Previous versions of the guidance and other related documents can be found on the Worms & Germs COVID-19 Veterinary Resources page.


We continue to track cases of canine infectious respiratory disease in various parts of Canada, for what it’s worth. The data are obviously a bit dodgy because it’s primarily from self-reporting, but I think we’re getting some interesting information. Cases seem to be slowing down, but we continue to get reports from the two main areas in Canada (and a trickle from the  US). Part of the clustering we’re seeing is probably due to local increased awareness and reporting, but I don’t doubt that a couple of reasonable-sized outbreaks have been ongoing.

Click here for the latest version of our canine infectious respiratory disease complex (CIRDC) map (December 31), now with the ability to display cases reported by month.  A snapshot of the map is also shown below.

Here are some additional details from the data we’ve collected via the reporting survey:

65% of affected dogs had been vaccinated against “kennel cough” in the past year.

  • That’s not too surprising. Kennel cough vaccines protect against one, two or three of the many potential causes of CIRDC, but not all of the causes, by any means. Furthermore, no vaccine is 100% effective. These data don’t tell us anything about how well those vaccines work (they actually work quite well).

Of that 65% of affected dogs that were vaccinated in the past year:

  • 40% were vaccinated orally: The oral vaccine only covers Bordetella bronchiseptica, which consistently comes in as the #2 cause of CIRDC in Canada. It’s a good vaccine for that bacterium but has less coverage than intranasal vaccines.
  • 29% got an intranasal vaccine: Intranasal vaccines in Canada cover Bordetella bronchiseptica and canine parainfluenza virus, giving protection against the top 2 causes or CIRDC. Some also include protection against canine adenovirus type 2.
  • 35% received an injectable vaccine: Injectable vaccines are less protective when it comes to CIRDC. Oral and intranasal vaccines provide better protection where the infection occurs – in the upper respiratory tract.
  • 26% were unsure of the vaccine type: So whether these dogs were truly vaccinated against kennel cough is unclear.

Over half of affected dogs had visited a dog park shortly before they got sick.

  • That’s not surprising at all, since CIRDC is spread dog-to-dog, and parks are a place where dogs congregate.  Groomers came in as the #2 most common previous contact, followed by doggie day care.
  • Since we just looked at sick dogs, we can’t say anything about risk factors (e.g. we don’t know if visiting a dog park was more common among sick dogs since we couldn’t compare them to healthy dogs).
  • There were a couple specific parks that were frequently named, so it’s likely there were some true hot spots of transmission at those parks.

Diagnostic testing was performed on 17% of sick dogs, but nothing remarkable was apparent in terms of diagnosis.

  • That’s actually a pretty high percentage for testing in cases like this. Testing isn’t commonly recommended for routine cases of CIRDC since the cost is hard to justify where there’s little impact of test results on individual patient care.
  • Testing is more useful when there’s an outbreak (to figure out what the culprit is and see if there are any control measures that might be applied), with imported dogs (worried about bringing in influenza strains), kennels (outbreak potential) and breeders (outbreak potential, risk of more severe disease in young and pregnant dogs).
  • Limited test results were provided on the survey but nothing remarkable was present.

Most of these outbreaks of CIRDC die out over time and we never find the cause.

  • Canine parainfluenza is always high on my list since it’s common (common things occur commonly) and can be missed with routine testing because the virus isn’t shed for long. By the time the dog is taken to a veterinarian and sampled, PCR tests looking for the virus may be negative (and other approaches like antibody-based testing aren’t usually done).
  • A “new” or (more likely) established but unknown cause of illness is certainly possible. There are undoubtedly many canine respiratory viruses out there that we don’t know about.
  • Introduction of canine influenza from imported dogs is always a concern. It’s a “foreign” disease, but canine influenza was introduced to Ontario a few years ago, and was ultimately eradicated (as far as we can tell).  Here, since there haven’t been any positive test results, it’s unlikely to be the cause. That virus is shed for a while in infected dogs, and I’d expect to see a positive result with a reasonable number of tests. Introduction of influenza into areas where few to no dogs have immunity to the virus would almost certainly result in more widespread disease. So, I think flu is pretty unlikely here, but the potential for flu is a reason to test. We’ve shown it can be controlled when it’s caught early, but if it’s not, it can cause a lot of damage.

Disease tracking like this won’t provide clear answers, but helps identify and refine things we need to look at, so I think there’s a role for it  as an easy, low-cost surveillance tool.

The new SARS-CoV-2 strain circulating in the UK (technically called SARS-CoV-2 VUI 202012/01, or B.1.1.7 – see “what’s in a name” below) has raised a lot of concern internationally. The fact that we have a mutant strain of the virus isn’t surprising. There are countless mutant strains out there already. Viruses like this naturally change over time. Usually the changes are fairly irrelevant in terms of how the virus behaves, though they can still be useful for tracking purposes. However, depending on the type of mutation and location on the virus genome, it can impact what the virus does in either a good way, or a bad way. Mutations are random, but if a certain mutation helps the virus survive and spread, those mutant strains tend to become more common.

What’s the deal with B.1.1.7 (or whatever you want to call it)?

This strain has multiple mutations (compared to other commonly circulating strains), and many of those mutations affect the spike protein. The spike protein is what the virus uses to attach to ACE2 receptors, which are found on the surface of human and animal cells. The better the match between the spike protein and the ACE2 receptor, the greater ability of the virus to attach to and infect cells. Differences in the ACE2 receptors impact species susceptibility (e.g. a person’s ACE2 receptor is a good match for the virus, so people can be infected. A bird’s ACE2 receptor is a very poor match so birds are resistant). The mutations in B.1.1.7 seem to make the spike protein a better match for human ACE2 receptors.

That’s likely why this strain seems to be much more transmissible to people than other strains, and it’s rapidly become a common strain the UK. It’s also been found in various other countries (typically with an epidemiological link to the UK).

How did B.1.1.7 emerge?

The ECDC’s Threat Assessment Brief mentions three main potential mechanisms for the emergence of this particular strain. They considered gradual accumulation of the collection of mutations in the UK to be unlikely, since this strain is a big jump from other strains in that country (i.e. intermediate generations of the virus with smaller numbers of these mutations weren’t found in the population before B.1.1.7 suddenly appeared). That left the following main considerations:

  • Prolonged infection of a single patient with SARS-CoV-2, which allows more mutations to occur quickly, with subsequent spread back into the general population.
  • Infection of an animal, with mutation in the animal and then transmission back to people.
  • Gradual emergence of the strain in another country that has little sequencing data, and then introduction of the strain to the UK.

I assume this strain originated in a person. However, movement of viruses between species can foster selection of mutants, and that’s why we’re paying close attention to how SARS-CoV-2 behaves in animals, especially large groups of animals like mink farms where there can be a lot of transmission. It’s also one reason we’re worried about infection of wildlife, as sustained spread in wildlife could potentially create lots of new strains.

What is the impact of B.1.1.7 on animals?

Increased affinity for human cells doesn’t necessarily mean increased affinity for other species’ cells. It might, or it might result in decreased affinity. Hopefully someone’s looking into that.

  • If this virus is equally transmissible to animals as its predecessor, we still have more human cases and that means more animal cases, just from more human-to-animal exposures.
  • If this strain can more easily infect certain animal species, we could see even more human-to-animal transmission, i.e. a higher occurrence of the spillover infections we’re already seeing.
  • Another concern is whether any new strain could infect species that are resistant to the current SARS-CoV-2 virus, including livestock and wildlife species. I doubt this set of mutations is enough to change the host range, but it needs to be considered.

How can we find out how B.1.1.7 affects animals?

Experimental studies are one way, but they’re not ideal in this case for a number of reasons. Field studies can be useful, looking at transmission of the new strain to animals in contact with infected people, as well as ongoing surveillance of animals in settings like mink farms. The issue is there are very few researchers doing things that way. Logistical challenges, as well as lack of coordination with the human health measures and testing, hamper timely testing of in-contact animals. We need to test animals when infection in their human contacts is first detected if we want to recover virus from them. Cooperation of local and provincial health authorities has been a challenge here, an understandable one though given the stress the system is under trying to manage the pandemic. It’s another example of why planning for this type of thing needs to be done in advance (as I said repeatedly post-SARS-CoV-1, and as I tried to address with the province in January 2020, with no response). The odds are good that animals won’t play a role in dissemination of this virus, but it would be nice to base that on data, not hope.

Will this new strain impact the most impressive vaccination development drive in human history?

Hopefully not. There is confidence that this mutation will not impact the efficacy of the current vaccines. However, it’s a reminder that we still have to control transmission as much as possible while vaccines roll out. Less transmission means fewer illnesses, fewer deaths and fewer mutations. We need to buy time until vaccines are available to everyone, everywhere, to reduce disease and the risk of significant mutations.

What does it mean for Canada (or the US, or any other country)?

It means we need to:

  • Control the spread of SARS-CoV-2, whatever the strain
  • Sequence more viruses to understand the presence and spread of different strains
  • Investigate potential animal sources
  • Vaccinate, vaccinate, vaccinate

What’s in a name? When it comes to a virus…

Just like we quickly tried to move away from calling SARS-CoV-2 the “Wuhan coronavirus,” we are trying to avoid calling this new strain a “UK variant.” It’s best referred to as a strain first found in the UK, or by its technical name (which unfortunately isn’t particularly short or catchy).  We shouldn’t be “shaming” countries that find pathogens or their variants and report them. Just because this new strain was first found in the UK doesn’t mean it originated there. We don’t want fear of blame, travel bans or things like that to be a disincentive for countries to test and report. Even if the virus emerged there, it’s not the UK’s fault (beyond the fact that more virus spread overall means more risk of a mutation like this occurring).  A mutation like this could have happened anywhere in the world and been imported to the UK, and then spread rapidly there after it arrived.

We’re continuing to track informal reports of canine infectious respiratory disease in a number of areas.  Click here for the latest version of our canine infectious respiratory disease complex (CIRDC) map (December 17).

We’re still getting lots of reports of sick dogs in Edmonton and Calgary, both via cases reported through our survey for the map and through emails that I get from various people.

The cause of illness in these dogs is currently still unclear. There have been a few positive tests for canine parainfluenza virus (our most common cause of canine infectious respiratory disease) and Mycoplasma (something I’m not convinced is truly a primary cause of disease in dogs), but nothing consistent. Limited testing and testing late in disease affect our ability to figure out what’s really going on.

Nonetheless we are seeing some clustering around specific parks and some cases linked to groomers, which is not uncommon in situations like this.

There are various reasons we’re paying attention to SARS-CoV-2 in domestic animals. One important one is the potential for transmission of the virus from domestic animals to wildlife (because animals tend to have more direct contact with wildlife than people do). More specifically, we’re concerned about transmission to wildlife and then persistence of the virus in wildlife populations. For that to occur, you need susceptible wildlife species in large enough numbers and in close enough contact with each other for transmission of the virus to be sustained over time.

There is emerging information about the susceptibility of a few common wildlife species, so there is basis to those concerns and a need for more study.

A lot of the concern about SARS-CoV-2 in animals has revolved around mink. They’re highly susceptible and farmed mink are kept close together in large numbers. That’s a recipe for virus transmission (and potentially virus mutation, but that’s a different story). Farmed mink are also good at escaping. “Wild” mink found around mink farms tend to be escaped mink, or the offspring of escaped mink.  Escaped farmed mink and wild mink can often be distinguished by certain physical characteristics including size (larger) and coat color (some farmed mink are bred for coat colours that don’t commonly occur in wild mink) .

When it comes to SARS-CoV-2, escaped mink create a few concerns. One is they could take the virus with them when they escape if they’re infected, creating another potential exit point from the farm for the virus. We don’t want that. The virus getting onto the farm is bad, but if it stays there and burns out, it’s not as big deal compared to the farm becoming a source of infection for other animals. Mink don’t shed the virus for long, so there would only be a short window of time after escape that a runaway mink would pose a transmission risk to other animals. Another concern is that if escaped mink continue to hang around the area (e.g. coming back to find food), they could become a longterm bridge for infectious diseases (e.g. SARS-CoV-2, and others) from the farmed mink to wildlife.  Or worse, if escaped mink move between properties in areas where mink farms are close together, they could spread diseases from farm to farm.

That’s my long-winded introduction to the latest concern with mink, identification of SARS-CoV-2 in a wild mink in Utah, USA. Some mink farm outbreak investigations have included testing of wildlife around the farm. Infected cats have been found in Europe, and testing of wild mink around an affected farm in Utah identified an infected animal there too. They’re considering it the first case in a “free ranging, native wild animal,” which I guess is correct, but I’m not sure it’s much different than the spillover to cats on and around mink farms that’s been seen before. Not surprisingly, the viral sequence from the affected mink was identical to that of virus from mink on the nearby farm.

What does this mean?  It’s too early to tell. One good thing about the SARS-CoV-2 virus is there’s no long-term carrier state, that we know of (at least outside of bats… that’s yet another story that still needs to be sorted out). If the virus makes it into wild mink or other wildlife, the relevance depends on whether that species can maintain and spread it. Infection of solitary species, species that have low population density, or species that aren’t very susceptible and don’t shed a lot of virus likely ends quickly. The concern is infection of large groups of susceptible animals, where infection might be self-sustaining in the population, circulating within and between groups (just like it does in people). At this point, we have no idea if that’s a realistic concern in wildlife, but it’s better to look and find out than just hope for the best.

Still, the best way to prevent this from becoming an issue is to prevent exposure of all animals as much as possible, especially wildlife. The best way to prevent that is to control it in people.

A few days ago, I wrote about our efforts to track infectious respiratory disease in dogs, based on informal reports of potentially increased disease activity in a couple of areas (particularly Calgary AB and Guelph ON).  Click here for the latest version of our canine infectious respiratory disease complex (CIRDC) map.

As expected, once we started asking, we started getting more reports of sick dogs in several areas. There are also some interesting potential links. For example, numerous cases from Edmonton have a link to Lauderdale dog park. It’s unclear whether that means there’s a true cluster associated with the park versus it simply being a very busy park frequented by a lot of dogs (sounds like it is) versus people being more likely to report exposure to that park. But it’s something to consider, and that’s a large reason why we do this kind of data collection. We’re not trying to get really accurate and specific information, we’re simply trying to spot trends and find things on which we can potentially act. The more data we have, the more we can hopefully figure out.

So veterinarians and dog owners, please keep reporting cases of dogs with suspected infectious respiratory disease through our survey, even if the signs are relatively mild. It’s quick and anonymous.

A few disclaimers:

  • The survey results and map are always going to be biased, since we depend on people to report cases. A cluster of cases can be a cluster of increased disease or a cluster of increased reporting.
  • For privacy reasons, we plot cases at the FSA level (forward sortation area, aka first 3 digits of the postal code). Where the dot ends up on the map isn’t reflective of the exact location of the reports. (As I said in a Tweet about dots on the map, please don’t yell at me if your house ends up under a dot. It’s not supposed to be that accurate.)

A few times a week, I get questions like this from veterinarians:

  • I have a canine patient from [name your country] and it’s sick. What diseases should I be aware of?
  • I have healthy canine patient that was just imported from [name your country]. What diseases should I be aware of?

Or I get questions like this from dog owners:

  • I’m getting a dog from [name your country]. Are there any disease concerns I should know about?

Or, less commonly, I get questions like this from physicians:

  • I have a sick (human) patient that adopted a dog recently from [name your country]. Are there any zoonotic diseases I should be thinking about?

We don’t have good international disease surveillance in dogs, or even a central database of the information that is available.  I’ve kicked around ideas to address this particular gap for a while, and Dr. Katie Clow and I have finally gotten something rolling as part of our broader canine importation research. Our goal is to make it easier for people to figure out some of the regional disease risks when importing or traveling with dogs, and to identifying zoonotic disease risks from dogs that have traveled or dogs encountered when traveling.

To do this we have created an interactive global canine infectious disease map. This is a VERY beta version, starting with a limited number of diseases, and there are almost certainly errors and omissions. The way we’re going to make this map most useful is with lots of ground-level input from different countries, especially those from where there’s little published information on infectious diseases of dogs.

We are soliciting input to identify any incorrect disease categorizations, relevant information that should be added to clarify infectious disease issues (if you hover over a country on the map, a comment box appears), and suggestions for the next diseases to add to the map.  Any comments can be sent to me at jsweese@uoguelph.ca, by Twitter @weese_scott or via the Worms & Germs Blog contact page.

Not surprisingly, COVID-19 has been identified on a mink farm in British Columbia, Canada, in the midst of Canada’s 2nd wave of the COVID-19 pandemic.

It’s important note that so far, the virus has only been found in people on the farm, not in the mink. Eight farm workers were reportedly diagnosed with COVID-19 over the weekend, so now testing of the mink is underway. With 8 infected people at the facility, it’s pretty likely that the mink are infected as well, since they are quite susceptible to the SARS-CoV-2 virus, but we’ll need to wait for the test results later this week.  If there are a few infected mink on the farm, that can become lots of infected mink pretty quickly.

This is a breaking story so more information will no doubt roll out over the next few days.

The big questions are:

Have the mink been infected with SARS-CoV-2?

  • We’ll know soon enough.

Has there been any mink-to-human transmission of SARS-CoV-2?

  • That’s a bit harder to discern, especially if all of the infected workers have had contact with each other. If the virus is detected in mink, sequence analysis and comparison of the strains in the mink versus the workers will be part of the picture.

Has/will the SARS-CoV-2 virus mutate in the mink (as was seen in Denmark)?

  • We’re still unsure about how much of a risk virus mutation is.  Mink farms have  large numbers of susceptible animals, making them good places for mutations to occur. Virus mutations are random events, so they may be good or bad. We’re worried about mutations that negatively impact control measures (like vaccination) or that could make the virus more transmissible or illness more severe IF the mutated strains spill back into people. As above, sequence analysis will be used to look for evidence of significant mutations.

Have other animals on or around the farm been infected with SARS-CoV-2?

  • Testing of any other animals on the farm (e.g. cats) and wildlife on the property will likely follow if the mink are found to be infected.