Rat bite fever is a bit of a niche disease but one that I talk about a fair bit because it’s often missed, or at least diagnosed a lot later than it could (and perhaps should) be.  It’s not an issue with technology or testing – it’s an issue of human behaviour and failing to ask a simple question.

Rat bite fever is a bacterial infection caused mainly by Streptobacillus moniliformis. This bacterium lives in then mouth of most rats, and people mainly get exposed from rat bites (hence the name). Typically, infection causes a febrile illness that’s readily treatable, but it can sometimes cause serious complications, and it can be fatal.

A recent paper in BMC Infectious Diseases (Adams et al., 2021) describes an unusual presentation of rat bite fever, but a pretty typical story overall.

The report describes a 55-year-old man with infection of vertebrae (bones) in his back. He went to the hospital because of severe back pain, and didn’t have any classical signs of infection. Imaging showed abnormalities in his back, and a sample from the affected area was collected. Bacteria were seen, and antibiotics were started. Culture eventually yielded Streptobacillus moniliformis.

This is an unusual presentation of an unusual infection.  There’s no reason someone in this situation would have thought “hey, this might be a weird case of rat bite fever” when the patient arrived. He also responded well to treatment, so it’s not one of the cases where missing the diagnosis early had a major impact.

The main reason to mention this case report at all is this statement:

On further history, it was revealed that patient had two pet rats and had sustained numerous bites in the last 1 year prior to symptom onset.

That’s often when this information is obtained…”on further history.” Animal contact is often not queried until after a (often late) diagnosis of a zoonotic infection is made.

Would it have changed anything in this case?  Probably not.  However, “do you have pets” or, preferably “have you had contact with any animals” is a simple question to ask right at the start. It takes little time and no money, but it can lead to a quicker diagnosis in some situations.

More information about rat bite fever is available on the Worms & Germs Resources – Pets page.

For this blog, I focus my writing on companion animal issues, but our group does much more than that, and a recent study of ours is worth a post here as well.

Antimicrobial resistance (AMR) is a huge issue globally. It’s a classic One Health problem with important human, animal and environment aspects, and it’s getting a lot more attention now as it’s become a genuine crisis.  We know we need to reduce and improve antimicrobial use in order to stem the tide of AMR. We already know a lot of things we can do to achieve that, and yet we often fail to use those tools.

Why aren’t we doing a better job of using available tools to help reduce antimicrobial use?

There are lots of reasons, but human behaviour is a big one. Despite knowing something is good, people are often resistant to change for any number of reasons, including but not limited to:

  • Culture (we do it that way because we’ve always done it that way)
  • Inertia (change requires effort, an it’s easier to just keep doing the same thing)
  • Lack of motivation to change when the problem isn’t immediately obvious (problems associated with AMR aren’t something most people see every day, and they’re often a “delayed” consequence of poor antimicrobial use, so that decreases motivation to alter practices)
  • Defensive medicine (the desire to treat something with antimicrobials “just in case”)

The last one is an area in which I’m particularly interested.  Sometimes, we (including physicians, veterinarians, farmers, animal owners and others) make treatment decisions based more on protecting ourselves, rather than the individual or group of animals we’re trying to help.

For example, let’s look at management of diarrheic diary calves (which are the focus on the study I mentioned).  Like most neonates, diarrhea is common in dairy calves. Most often it’s mild, but sometimes it can be serious and even fatal. On many farms, most or all diarrheic dairy calves are treated with antibiotics. Yet, we know that most don’t need them.

So why do so many diarrheic calves get treated with antibiotics?

  • Sometimes it’s lack of understanding of when antibiotics will actually be effective.
  • Sometimes it’s simply based on fear of what might happen if they don’t get antibiotics.

If a person’s job is to raise calves on a farm and a calf gets diarrhea, it’s often their decision how to treat the calf.  This is often (and should be) based on a protocol or decision tree developed with the farm veterinarian, but a veterinarian is not always involved in every treatment decision.  But more often than not, that person is going to err on the side of giving antibiotics, versus not.  In our study, we heard from calf caretakers that their thoughts are along the lines of “If the calf gets really sick or dies and it didn’t get antibiotics, it’s my fault.” So, there’s a psychological barrier to not treating. At the same time, the downsides of treating include cost of the drugs (but that’s considered a cost of doing business that no one focuses on), hassle (ditto) and the risk of promoting AMR. However, resistance isn’t as “in your face” on a farm as a dying calf, so instead the focus tends to be on the uncommon, bad outcome (i.e. the calf dying) and resistance it gets written off as an inherent, unavoidable risk that’s someone else’s fault.

So, we’ve heard many say things like “I know I don’t need to use antibiotics in most situations, but it’s my neck that’s on the line if something happens.”  Human behaviour, not biology, is the biggest barrier.

That’s a long winded introduction to a recently published paper that was part of Dr. Diego Gomez’s PhD program, in which we assessed a simple algorithm (below) to help decide whether or not to treat a diarrheic calf with antibiotics.

The algorithm that can be easily applied at the farm level, and it achieves a couple things.

  • It provides more evidence for decision making and education about when antibiotics are are recommended.
  • Probably more importantly, it provides a “cover your butt” component for the people making the treatment decisions on farm. By shifting the decision to an algorithm, concern about blame gets deflected too. Rather than worrying about taking the heat for a bad outcome in a calf, the decision-maker now has some backing (or someone else to blame), making it easier to make the decision they maybe always wanted to make.

So, did using the algorithm actually help decrease antimicrobial use in diarrheic calves?

Yes! There was a significant drop in frequency of antimicrobial treatment on most farms, though not all.  The differences between farms probably relate to how good a farm’s management practices were to begin with, as well as how much they trusted the algorithm (e.g. a farm that was already doing a good job limiting antibiotic use wouldn’t see as much of an improvement).

Overall, across 10 farms, there was a major drop in antibiotic treatment of diarrheic calves.

  • Before the intervention, 85% (1303/1573) of calves were treated.
  • After the intervention, just 18% (310/1698) of calves were treated.

All with a simple algorithm that costs absolutely nothing to use.

AND – very importantly – there was no adverse impact on calf health. Decreasing antibiotic use didn’t’ result in more seriously ill or dead calves, supporting the notion that most diarrheic calves don’t need antibiotic treatment.

Canine influenza is back in the news in the US, with close to 50 dogs infected with canine influenza at a dog rescue in Florida.  The outbreak has been going on for over two weeks already.  This is a “surprising but not surprising” scenario to me.

It’s a bit surprising because canine flu activity seems to have been really low to non-existent in the US lately. While there’s no formal surveillance program, I haven’t seen reports of it and haven’t heard any other chatter about diagnoses.

It’s more towards unsurprising though. We were able to eradicate canine influenza (as far as we can tell) in Ontario, Canada, when it hit here in 2018, but that took a lot of surveillance and effort, and we intervened very quickly after introduction of the virus. With widespread disease in the US over the years after multiple introductions from Asia and no broad control plan, it was expected that canine flu would continue to spread on this continent – sometimes insidiously, sometimes dramatically. Since the virus is so transmissible and vaccine coverage is low, it can spread quickly, but disease can also burn out in a particular area if infected dogs don’t continue to meet susceptible dogs.

While we weren’t seeing reports of infections, it seemed optimistic to assume it had completely disappeared, and even if it did, importation of dogs from areas where the virus is endemic poses ongoing risk of reintroduction and spread.

It would be nice to know a few things about the reported outbreak in Florida:

  • How solid is the diagnosis? The reports say “canine influenza” but sometimes people get confused and default to saying “flu” for any respiratory disease, or don’t realize there’s a difference between canine influenza and parainfluenza (a very common respiratory virus in dogs worldwide).
  • Assuming this really is canine influenza virus, what strain is it? Is it our expected H3N2 canine flu strain, or could it be something new? (which would also have huge implications from a vaccination standpoint)
  • How did the outbreak start? The rescue says a dog “from the area” brought it into the facility, but where did that dog likely get infected? Unknown-origin infections suggest there could be more transmission going on than we realize.

If this is H3N2 canine influenza (which is the most likely strain), that leads to questions about vaccination. We have an H3N2 canine vaccine in Canada and the US. (We also have a vaccine that covers H3N8 in dogs, but that strain hasn’t been seen in years.) Canine flu vaccines are like human flu vaccines – they’re designed to reduce the likelihood and severity of disease, but they’re far from perfect and may not do a lot for preventing transmission overall. However, they are still useful.

When I think about use of influenza vaccines in dogs, I consider two main factors:

  1. Likelihood of exposure: Dogs in the area of this rescue would obviously be at increased risk of exposure to the virus. Dogs that have contact with imported dogs (e.g. dogs in a rescue that periodically imports dogs) and dogs that travel to areas where the virus is, or may be, present, would also be at increased risk of exposure.  This dogs are more likely to benefit from vaccination.
  2. Likelihood of severe disease: My 8-year-old otherwise healthy Labrador is unlikely to have a severe outcome if he’s infected with influenza virus. If he was a bit older, had respiratory or heart disease, had other debilitating issues or was a brachycephalic breed (like a bulldog), the odds of him having a severe (or even fatal) outcome from infection would presumably be much higher. Vaccination is therefore more important in dogs in these groups. All the deaths we saw here in Ontario from canine flu back in 2018 were in senior dogs. However, severe disease can still occur in younger dogs. So, vaccination is more important in higher risk dogs, but that doesn’t mean it’s not useful in others.

We’ll have to see how this story plays out, hopefully more information will follow.

A brief report in the latest edition of the Canadian Medical Association Journal describes a child with lymphadenopathy (swollen lymph nodes) due to cat scratch disease.

I was a bit surprised to see a straightforward case like this published in such a journal, but it’s a good reminder of a few issues.

Cat scratch disease is caused by the bacterium Bartonella henselae, and it’s a common (and probably commonly missed or misdiagnosed) disease.  The bacterium can live in the bloodstream of cats, where it usually doesn’t cause a problem. People typically get exposed through fleas that feed off the cat, ingest the bacterium from the cat’s blood, and then pass the bacterium in their feces (“flea dirt”) which then comes in contact with people. Cat scratches are often linked to human infections, not because the bacterium is living on the cat’s claws, but because claws create an opening for the bacterium to get into the body through this exposure to flea dirt, or if there are flea feces on the cat’s claws from grooming or scratching itself. Contact with flea-infested cats, especially young stray kittens, is a big risk factor for infection in people.

The story in this case report is pretty straightforward:

  • A 10-year-old boy was presented with a 10-day history of worsening elbow pain and intermittent fever, and no response to empirical antibiotics.
  • He had been bitten by a stray kitten 4 weeks earlier. The bite likely wasn’t the issue in this case, but was an indicator that he had close contact with the cat, and presumably was exposed to flea feces. The bite could have inoculated flea feces from his skin into his body.
  • Swollen lymph nodes were identified, and extensive testing revealed only Bartonella henselae in his blood, in terms of a potential cause.
  • He responded quickly to appropriate antibiotics for Bartonella henselae.

That’s a pretty typical presentation of this disease – low grade fever, enlarged lymph nodes and a bump at the scratch site are most common. However, more serious infections can occur rarely.

The authors concluded: “Physicians should consider cat-scratch disease in their differential diagnosis of regional or unilateral lymphadenopathy.”

True.  However, the bigger statement to me should have been “Physicians should routinely query animal contact.” Zoonotic infections are often missed or diagnosed late because of failure to ask a simple question about animal contact.

Interestingly, there’s no mention about the child being given rabies post-exposure prophylaxis, which is surprising after a bite with a stray cat. Maybe it was done and they didn’t report it. Or perhaps the stray cat was captured and they were able to keep it under observation for 10 days to rule out rabies shedding at the time of the bite.  If not, rabies would also be a concern.

As I mentioned recently, we’re tracking anecdotal reports of increased respiratory disease activity in dogs in Ontario.  If you have observations or cases to contribute/report, please take a few minutes to fill out our short survey here:


Infectious respiratory disease is endemic in dogs everywhere, so there’s always some disease activity going on. Sometimes we see what are likely true outbreaks, caused by either by our usual suspects or by something we haven’t yet identified. Sometimes the “outbreaks” are actually just more attention being paid to the normal level of disease.

Usually infectious respiratory disease is self-limiting in dogs – they cough, have a runny nose and eyes and feel run down for a few days, and then they get over it on their own. It’s really just like people with the common cold. However, sometimes more severe disease can occur, and I’ve had what I’d consider a lot more reports of serious disease lately, so we’re trying to sort out what’s happening.

So far, there’s not much to report. Some of our preliminary case maps are below; the size of the dots corresponds to the number of cases reported from that area. At this point, most reported cases are in Toronto, but there are also more dogs and more people there, so we have to be cautious not to over-interpret that.

Most reported cases have also been in dogs not vaccinated against “kennel cough.”  Those vaccines only cover some of the potential agents of canine infectious respiratory disease complex (CIRDC), namely Bordetella bronchiseptica, +/- canine parainfluenza virus, so it’s hard to interpret that result with the limited information we have so far too.

Limited diagnostic testing has been performed, which isn’t surprising. Testing doesn’t usually influence care of the individual dog so most owners don’t want to pay for it, and we don’t actually recommend it as a standard tool (although it would potentially help us in situations like this).

More updates will follow if I get more reports.  Please fill out the survey if you have additional cases to contribute.

Key points for any concerned pet owners:

  • If your dog is sick, keep it at home.
  • Don’t let your dog interact with sick dogs. In particular, try to stay away from dogs that are coughing, or have runny eyes and a runny nose. (I know, that’s not easy in some situations.)
  • Consider “kennel cough” vaccination if your dog regularly encounters other dogs (talk to your veterinarian).
  • Preventing exposure at places like parks where your dog may encounter many other dogs of unknown health status is tough. If you’re concerned or your dog is at higher risk for complications (e.g. old, pre-existing respiratory or heart disease, brachycephalic breed like a bulldog), be more restrictive about your dog’s contact with other dogs, and talk to your veterinarian about the value of a “kennel cough” vaccine.

The latest version of A Guide to Mitigating the Risk of Infection in Veterinary Practices During the COVID-19 Pandemic (15-Jun-2021) has been released.  It can also be accessed through the Ontario Veterinary Medical Association Coronavirus FAQ webpage (member login required).

The main changes are a new section summarizing various considerations for re-opening of veterinary practices to clients, and minor updates to other areas such as ventilation.

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

I get asked about this topic a lot. Early in the pandemic, I wrote a post about options for caring for pets of people with COVID-19.  Some things have changed a bit now that we know more know about SARS-CoV-2 in animals and the associated zoonotic risks, and we have a vaccine for people.

One example of a commonly encountered scenario is: A dog owner is being hospitalized because of COVID-19 and a friend or family member has been asked to take care of the pet.

What are the risks to the caretaker of the dog?

  • We don’t know. I’d consider it very low but I can’t say it’s zero.
  • Person-to-dog transmission of SARS-CoV-2 is fairly common in households where the owner has COVID-19, based on our and other groups’ surveillance efforts. However, dogs are not really a great host for this virus and infections are probably fairly low grade and transient, and therefore low risk for further transmission.
  • Dog-to-dog transmission of SARS-CoV-2 hasn’t been seen experimentally, but the studies to date have been fairly small so we can’t read too much into that.  Nonetheless, it’s clear that dogs are lower risk than cats for passing the virus on to other individuals. Yet, live virus has been grown from canine respiratory secretions, suggesting there is at least some plausible risk.

What can or should be done in this situation?  There are two key considerations:

1. Should the person in question agree to look after the animal at all?

  • This requires consideration of the risk status of everyone in the household (e.g.  is anyone at high risk of serious disease if they get infected?), vaccination status of everyone in the household, whether other pets are present, how well the dog can be contained in the household, and whether the household members are willing to accept a small degree of risk.
  • The best case scenario is to send the dog to a pet-free household where everyone is vaccinated and where they can keep the dog away from other people or animals (e.g. they have a fenced yard). Asking someone else to look after a pet like this was harder earlier in the pandemic, but now that we have highly effective vaccines, it’s easier.  Asking if someone from a fully vaccinated household will take the job is reasonable.

2. How should the dog be managed?

  • That also depends on the risk status of the household. In a vaccinated household, I’d say it can be “business as usual” in the house, but restricted outside. By that, I mean I’d do nothing different with the human-dog interactions in the household, but when the dog goes outside it should be under control (e.g. on a leash, or in a fenced yard) so the dog doesn’t interact with other people or dogs from outside the household.
  • If there are unvaccinated people in the household, it’s tougher. I still consider the risk of transmission from a dog to be very low, but I can’t say it’s zero. So, it would be prudent to keep the dog away from unvaccinated individuals as much as possible for the first 14 days (7 days is probably reasonable if it’s a major issue, but 14 days is ideal).  That doesn’t mean locking the dog in the bathroom and never going near it, but rather avoiding contact with respiratory secretions, not having the dog in the same small airspace for prolonged periods of time (e.g. not sleeping in the bedroom), and focusing on good hand hygiene.

The main issue is we just don’t know the risk. It’s definitely very low and could be zero, but I don’t think we can say it’s zero at this point. Vaccines are a game changer for these scenarios.

Okay, but what if the pet in question is a cat instead of a dog?

That changes the risk a bit, but not really the overall approach. Cats are more susceptible to SARS-CoV-2 and cat-to-cat transmission can occur, so there’s also more concern about the potential for cat-to-human transmission.  That means the issues above all apply to cats as well, but are probably heightened.

My focus here would be on finding a vaccinated household to look after the cat, if possible.  If not, it’s a matter of restricting contact with anyone who isn’t vaccinated. The good thing about cats is they are (for the most part) easier to contain than dogs.  They can be kept in a large cage or kennel if necessary, or they can be confined more easily to certain areas of the house, and cats don’t need to go outside. So, if someone who’s unvaccinated has to take in a cat, it’s easier to limit contact. The concepts above still apply, with a goal of minimizing the closeness and duration of contact during the first 7-14 days after the cat is removed from the person who was infected with COVID-19.

We’ve seen some increased awareness of the risks associated with dog importation, and countries taking measures to reduce disease and welfare problems, including here in Canada and more recently potential future measures in the UK.

The US just raised the bar a huge amount with new restrictions on importation of dogs from over 100 countries considered high-risk for canine rabies, which were announced today.  Starting July 14, 2021, dogs from those countries will not be allowed into the US, except for those with advanced approval on “an extremely limited basis.” Dogs from those countries that show up at the US border without pre-approval will be returned to their country of origin at the importer’s expense.

This is a logical move to try to curtail high risk activities that could potentially result in the importation of rabid dogs. It will interfere with some legitimate rescues, but more importantly it will impact massive puppy mill exporters and puppy brokers. Whether that will just drive those dogs to other countries (e.g. Canada… we import huge numbers of dogs from countries on this list) is unclear.  It will be interesting to see if other countries follow suit with similar restrictions.

The full list of countries considered high-risk for rabies is below:


  • Algeria, Angola
  • Benin, Botswana, Burkina Faso, Burundi
  • Cameroon, Central African Republic, Chad, Comoros, Côte D’Ivoire (Ivory Coast)
  • Democratic Republic of the Congo, Djibouti
  • Egypt (Temporary importation suspension of dogs from Egypt until further notice)
  • Equatorial Guinea, Eritrea, Eswatini (Swaziland), Ethiopia
  • Gabon, Gambia, Ghana, Guinea, Guinea-Bissau
  • Kenya
  • Lesotho, Liberia, Libya
  • Madagascar, Malawi, Mali, Mauritania, Morocco, Mozambique
  • Namibia, Niger, Nigeria
  • Republic of the Congo, Rwanda
  • Sao Tome and Principe, Senegal, Sierra Leone, Somalia, South Africa, South Sudan, Sudan
  • Tanzania (including Zanzibar), Togo, Tunisia
  • Uganda
  • Western Sahara
  • Zambia, Zimbabwe

Americas & Caribbean

  • Belize, Bolivia, Brazil
  • Colombia, Cuba
  • Dominican Republic
  • Ecuador, El Salvador
  • Guatemala, Guyana
  • Haiti, Honduras
  • Nicaragua
  • Peru
  • Suriname
  • Venezuela

Asia and the Middle East, Eastern Europe

  • Afghanistan, Armenia, Azerbaijan
  • Bangladesh, Belarus, Bhutan, Brunei
  • Cambodia, China (excluding Hong Kong and Taiwan)
  • Georgia
  • India, Indonesia, Iran, Iraq
  • Jordan
  • Kazakhstan, Kuwait, Kyrgyzstan
  • Laos, Lebanon
  • Malaysia, Moldova, Mongolia, Myanmar (Burma)
  • Nepal, North Korea
  • Oman
  • Pakistan, Philippines
  • Qatar
  • Russia
  • Saudi Arabia, Sri Lanka, Syria
  • Tajikistan, Thailand, Timor-Leste (East Timor), Turkey, Turkmenistan
  • Ukraine, United Arab Emirates, Uzbekistan
  • Vietnam
  • Yemen

I get calls about concerns regarding increased respiratory disease in dogs all the time.

  • Sometimes, they’re the result of local disease outbreaks.
  • Sometimes, they’re just a result of increased awareness of the normal “baseline” disease rate, since “kennel cough” is always occurring at some level.
  • Sometimes, the circumstances just seem different, and we need to get more information.

The last of these is where I stand at the moment. I’ve been getting more reports of canine infectious respiratory disease, including a concerning number of reports of severely affected dogs (with some fatalities). My impression is that something unusual is happening. Most often, the cause is actually one of our “usual suspects,” – the bacteria and viruses that normally cause canine infectious respiratory disease complex (CIRDC). It’s often very difficult to sort these things out because limited testing is done, there are limitations on the testing that is done, and there’s no formal tracking system for these infections.

However, we want to figure out what’s going on if we can, because sometimes we do see new (or new-to-us) pathogens (like when canine influenza hit Ontario in 2018), or we can identify hot spots for disease transmission (we’ve implicated specific dog parks in the past).

So, once again, we’re trying to track respiratory disease cases in dogs in Ontario (and beyond Ontario, if people want to report them). We have a quick online survey to collect more information and hopefully figure out if something unusual is happening and what it might be.  The survey can be accessed here: https://uoguelph.eu.qualtrics.com/jfe/form/SV_eP6E6AzIiJfnDlY