Following up on a recent post regarding evidence for shortened duration of treatment in select cases of feline infectious peritonitis (FIP), we have a new WormsAndGermsPod quick-bite on FIP treatment duration.

This short 14-minute podcast covers:

  • If/when can we shorten the duration of antiviral treatment for FIP
  • The issues to consider
  • The data (old and new) we have available

Check it out on Apple Podcasts, Spotify and most common podcast directories, or click here to go directly to the podcast in your web browser.

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A lot of infectious disease events get over-hyped by the media, which makes it a bit surprising that this case has flown a bit under the radar. It’s not a sign of an impending “influenza apocalypse,” but it’s a warning sign that more may be going on lately with flu viruses than we’ve been able to observe directly.

The CDC has confirmed a case of H5 influenza infection of a person in Missouri who had no reported contact with animals of any kind. The virus has only been identified as H5 or H5Nx, which means they have not confirmed the N-type, so we can’t say if it’s the same as the H5N1 influenza that has been circulating in wild birds since 2022, or in dairy cattle in the US since spring 2024. It’s surprising that the N-type has not been determined yet, since the infection was detected over 2 weeks ago – but knowing the strains that are circulating in the US right now, I’d say it’s almost certainly H5N1. (Sometimes sample quality can impede the effectiveness of molecular diagnostics too.)

Human H5N1 infections linked to the ongoing massive multiyear avian influenza outbreak have been rare. There have been just 14 reported H5 infections in people in the US so far in 2024, despite a huge amount of potential exposure, particularly among livestock and poultry workers. All previous human infections have been linked with direct and close contact with infected animals.

Rare spillover infections like these are largely expected when there’s lots of disease in animals. The worry is the potential for the virus to change to become amenable to human-to-human spread, so finding a human infection like the one in Missouri with no direct link to animals raises a lot of concern. The source of exposure in this case has not been determined. Details are sparse, but the person was reportedly hospitalized and recovered, and H5N1 testing was done as part of ongoing surveillance.

How could a person get H5N1 without animal contact?

  • Unreported animal contact, possibly due to incomplete history taking, or poor recall or unwillingness to report contact on the part of the patient for some reason)
  • Contact with a surface contaminated by an infected animal
  • Ingestion of contaminated food products

We hope the source of infection in this case was one of those. Hopefully they queried all animal contacts, not just birds and cattle, since we’re also concerned about infection from susceptible species that can bridge bird, cattle and and human populations (particularly cats).

Otherwise, we get concerned about the last option:

  • Contact with another infected person

As has been pretty common, details have been slow in being released. More information is needed about the person’s history, including whether the person had any human contacts that were high risk for exposure (e.g. worked with infected animals), and the genome of the virus to see if it’s consistent with the circulating avian strain, the strain that jumped to dairy cattle, or something different, and whether the strain has any genetic markers that indicate it could be more adept at spreading person-to-person. Missouri hasn’t reported H5N1 in cattle, but it’s circulating in wild birds, with spillover into poultry and backyard chickens. Missouri doesn’t have a huge dairy industry, but there are still lots of dairy cattle around and it doesn’t sound like there’s been much testing (a report in July said that only 17 of the state’s approximately 16,000 dairy cattle had been tested), so we can’t rule out local dairy cattle (or unpasteurized milk) as a source either.

Hopefully this is an oddball infection that died out when the person recovered, i.e. they got infected somehow but didn’t pass it on to anyone else. However, even if that’s the case, this event demonstrates why we need to have comprehensive and nimble influenza surveillance.

  • If the infection is indirect linked to dairy cattle (by finding the dairy cattle strain in the person), it shows again that the US has to take dairy cattle infections more seriously. H5N1 in dairy cattle should be containable with short term but aggressive movement restrictions, testing and infection control measures – short term pain for long term gain. Fewer infected farms are being reported lately, which is great, but it’s still spreading across the country. The longer the outbreak lasts, the greater the chances of interspecies spillover and for the virus to adapt to a new host.
  • If the infection is somehow linked to wild birds, that’s a tougher situation, since controlling the virus in wildlife populations is challenge, to put it mildly.

This case was detected as part of surveillance program. That’s great, in that surveillance found something important and led to an action: an investigation of possible sources and a warning that there could be more. The not-so-great part is that few people with flu-like disease get tested at all, including for H5N1 influenza. If human-to-human spread is occurring, it could easily slip under the radar if there’s insufficient testing happening. That’s particularly true if most infected people only get mild disease, as they’re even less likely to get tested. We don’t know whether this was a lucky detection of a very rare situation, or a more common problem that’s been flying under the radar. Only more time and testing will tell us that.

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We started WormsAndGermsBlog on a bit of a whim. I didn’t really know much about blogs but Maureen Anderson and I we were working on a project to develop infectious and zoonotic disease resources for different audiences, and realized that making physical flyers (or CDs… remember those?) wouldn’t be overly impactful or sustainable. Around that time, I was at the Ontario Veterinary Medical Association conference and Dr. Doug Powell of barfblog (a food safety blog) fame was talking about their work.

So, I looked into and… WormsAndGermsBlog was born.

We had no idea what to expect, and not a lot of expectations, but it’s been good. Since the blog’s been fun, I figured we’d try something new to get information out, and hopefully have some more fun in the process.

So… WormsAndGermsPod was born.

We’re just starting out, so our catalogue’s pretty sparse, but hopefully the podcasts we have so far are useful (and maybe entertaining), and we’ll be adding to them.

Episode 1 is what I’m calling a “quick bite” – a short discussion about a topic I get asked about a lot: “Is methicillin-resistant Staphylococcus pseudintermedius (MRSP) zoonotic?“

Episode 2 is our first full-length podcast, and fittingly is with my partner in crime, Maureen, about one of her areas of expertise, rabies (particularly in Ontario).

You can find us on Spotify, Apple Podcasts, iHeartRadio, Amazon and other podcast services.

Suggestions for future topics are always welcome!

Warning: long post. TL;DR? We can drop the antiviral treatment duration for feline infectious peritonitis (FIP) to 42 days in many situations.

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In veterinary medicine, a lot of our recommended durations for treatment for different diseases have little scientific backing. We “inherited” a lot of these treatment regimens from the days when the drugs were first used, when we had to try something, and as we tend to be risk averse and err on what we assumed was the side of caution, the initial treatment durations were longer more often than not. Unfortunately, rarely are subsequent studies done to refine such treatment durations to see how short we can make them while still being effective. People (not just in veterinary medicine) are often hesitant to try shorter treatments because we are risk averse and don’t like to change. There’s often pushback against using treatments that are shorter than the “standard” duration, despite the fact that the standard duration was originally just a guess that seemed to work. Duration of treatment is a big issue that I deal with every day with antibiotic treatment, but it’s also an issue with the use of other drugs, including antivirals.

Antiviral treatment with GS-441524 (GS) and remdesivir for feline infectious peritonitis (FIP) has been truly game changing. It’s taken an almost invariably fatal disease and made it usually successfully treatable (as long as we don’t start treating too late). As of 2024, these drugs are now also legally accessible to veterinarians in North America.

The current “standard” treatment duration for FIP is 84 days (12 weeks). Why 12 weeks? Ultimately a duration had to be picked to start, and that’s the number that was chosen. We’ve stuck with it not because cats necessarily need 84 days of treatment, but because 84 days seems to work.

  • However, it would be better to shorten the treatment because the drugs are expensive, and treatment can be stressful on the cat (and sometimes the owner).
  • GS is a very safe drug, but remdesivir can cause nasty injection site reactions, so there’s a safety issue with longer treatment too.
  • Cost may be the biggest driver, as a lot of infected cats are in the care of rescues and shelters, which typically have very limited resources.

A recent study from Germany that we’ve been waiting to see in press (Zuzzi-Krebitz et al. 2024) has shown that we can likely reduce the duration of treatment to 42 days, at least in some cats. It was a randomized controlled trial (yay! we don’t get these done very often in veterinary medicine) that took cats diagnosed with FIP and randomly assigned them to get either 42 or 84 days of treatment with GS-441524 (15 mg/kg once a day). The cats were followed for 168 days to look at their response to treatment and to look for relapses. They enrolled 40 cats, which is a fairly small sample size, but not surprising since these studies are hard to do. There were 20 cats in each treatment group.

  • One cat in each treatment group died (one was on day 3 and one on day 31) so the duration of treatment had no impact on survival. (This also shows how game-changing this treatment is, resulting in a 95% survival rate for a devastating disease that when untreated can have an equally high fatality rate.)
  • All cats in both groups that survived to the end of their treatment course were in complete remission on day 168. That’s not a guarantee that none of them relapsed later, but 168 days is a pretty solid follow-up period.

The study used legally produced, compounded GS-441524 from BOVA in the UK. (That’s the same source used for importing these drugs to treat cats in Canada; BOVA has also partnered with Stokes in the US to provide access to the drug there too as of this summer). Using legitimate, pharmaceutical grade drug (versus black market or questionable compounding of research grade molecule) is another strong point of this study. It used a drug formulation in which we can have confidence in the quality and consistency, and that applies to what we’re using to treat cats here in Canada. BUT I would not extrapolate these results to treatment of cats with black market FIP drugs.

Does the drug dose matter?

I would also be a bit wary of extrapolating these results to cats treated with at the 10 mg/kg/day dose, which is a common treatment regimen for non-neurological and non-ocular FIP. Ideally we’d have data on duration of treatment for other dosing regimens too, but that’s probably not going to happen in the short term. That raises the question of whether we should move to the 15 mg/kg/day used in this study. How these results relate to the newer suggestion of using twice daily dosing is also unclear. I’d be more comfortable extrapolating this to 7.5 mg/kg twice daily (which is the same total daily dosage) than 10 mg/kg/day.

So, if someone is considering using a 42 day treatment instead of 84 days, I’d definitely use 15 mg/kg/day or 7.5 mg/kg twice daily.

Also note that this study focused on cats with effusive (wet) FIP.

There was one cat with neurological FIP and one with ocular FIP (one in each group) and they both survived. This could suggest that short durations are okay for these other forms of the infection, but I’d be really wary of making that call on a single case in the 42 day group. So, I would be hesitant to extrapolate these results to other forms of FIP. If there were compelling reasons to do so in a particular case, I’d be okay with a 42 day course in a cat with neurological or ocular FIP that responded really well to treatment. However, I’m a bit wary of saying we should move all of these severe cases to 42 days of treatment without more data and experience.

Finally, we need to remember that each patient is different. Response to treatment has to be part of the decision. If response is slow and incomplete at 42 days, that’s probably not a good stopping point.

As a small study, it certainly has some limitations, but this is a key study that gives us support to treat some (if not most) cats with FIP for a shorter time. That will be critical for situations in which cost is a barrier, both for shelters/rescues and homed cats. It’s one more step to making FIP a more easily treatable disease.

Thanks to the authors for doing the study.

Thanks to the cat owners for being willing to be part of the study, in which their cat might have been assigned to the group that received a shorter-than-typical treatment course.

  • That’s a big deal, because people can be reluctant to sign onto a study where they are worried about the effectiveness of one of the approaches.
  • If the study is looking at a new drug versus an old drug, there’s often optimism about the new drug, and people often hope to be be assigned to that group.
  • For studies about shorter treatment durations, there’s less motivation to be in the non-standard group, especially if the drug costs are covered either way, so there’s no cost benefit to the cat owner. However, cost can also be a motivator to participate in a study like this if the owner could not afford or didn’t want to pay for treatment of any duration.

Today, we have a guest post from One Health epidemiologist extraordinaire (and great collaborator) Dr. Katie Clow and extraordinaire-in-training Sydney DeWinter.

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If you have been following the ongoing saga regarding canine importation regulations put forth by the US Centers for Disease Control and Prevention (CDC), dog movement is likely top of mind and you may be curious as to why regulations are needed in the first place. One of the biggest reasons is to prevent (or at least reduce the chances of) new infectious diseases entering a country. While we won’t spend time discussing all the diseases that sick (and seemingly healthy) dogs can bring on the plane with them, there is one disease on which we are regularly consulted and requires some additional considerations, and that’s canine leishmaniosis.

Let’s start by understanding the basics of this disease.

Canine leishmaniosis is a devastating disease caused by infection with blood-borne parasites of the genus Leishmania. These parasites are mainly spread through tiny biting sand flies, but can also be spread through breeding and from an infected mum to her pups. Across the world, canine leishmaniosis cases are documented in over 90 countries, so dogs imported from these countries could have been exposed to and be carrying the parasite when they arrive.

Next, we need to consider what these parasites actually do to a dog.

Leishmaniosis is a very complex disease with some dogs never becoming sick while others experience a range of clinical signs, many non-specific, from weight loss to skin lesions to fatal kidney disease. Dogs can be exposed and become sick months to years later, long after they have settled into their new homes in Canada. With the variable and non-specific presentation of disease, coupled with potentially long delays between exposure and disease, canine leishmaniosis can be a very tricky disease to diagnose.

Right now, we know that dogs are routinely being imported from countries where they could have been exposed to Leishmania spp., but we don’t know much else about this disease in Canada. For example, we don’t know how many imported dogs are infected, what medical and lifestyle risk factors exist, and how owners and veterinarians pursue treatment and access the applicable medications in Canada. This information is needed, as identified by many veterinarians who call for advice on case management and prognosis.

If you’d like to contribute to filling some of these knowledge gaps, we have two open studies, which have been generously supported by the American Kennel Club Canine Health Foundation. Here are the details:

1. Cross-sectional study to estimate the prevalence of infection with Leishmania spp. in imported dogs and identify lifestyle and medical risk factors associated with infection.

This study is recruiting dogs who have been recently (within last three years) imported from a country endemic for canine leishmaniosis. A blood sample will be collected from these dogs, and owners will be asked to fill out a questionnaire on the known lifestyle and medical history of the dog. Owners and veterinarians will be informed of the results from the blood sample testing. Costs for blood collection and testing are covered.

2. Case series study to describe the clinical outcomes of imported cases of canine leishmaniosis.

This study is recruiting dogs who test positive for Leishmania spp. infection and are displaying clinical signs. Blood and urine samples will be taken from dogs twice over a two-year period, and owners will be asked to complete a questionnaire at the time of diagnosis/enrollment, and then twice more (12- and 24- months post diagnosis). Testing costs are covered as well as veterinary time.

If you believe your dog may be eligible for either of our studies, or are a veterinary professional who knowns of patients who may be eligible, please email Sydney at sdewinte@uoguelph.ca.

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When mpox (formerly monkeypox) started to surge in Ontario back in 2022, I set up a study to try to look at possible human-to-pet transmission of the causative virus (known as MPXV), because we have very little information about the potential risks to pets, and their potential role in transmission. By the time we got all the animal care and ethics approvals, the outbreak had already slowed down considerably, and I was ultimately able to test a grand total of one (1) potentially exposed dog (it was negative).

The World Health Organization has once again declared mpox a global health emergency in 2024. With mpox is surging again, there (unfortunately) might be more opportunities to once again study transmission of MPXV between people and pets here in Canada and elsewhere. Recruiting pet owners and pets for testing in situations like this is tough, as we’ve seen before with SARS-CoV-2 and H5N1 influenza, but it’s data we really need to inform decisions and recommendations to control the spread of the virus.

Information on human-to-pet mpox transmission is still very limited. Two potentially infected animals were reported during the global outbreak in 2022 – a dog in France and a puppy in Brazil. However, there was some debate about whether positive results were from true infection or just contamination of the pet’s skin with viral bits from the infected humans in the same households.

Fortunately, we now have some new information from the US. An ahead-of-print article in Emerging Infectious Diseases (Morgan et al. 2024), describes an investigation in the US between July 2022 and March 2023. They collected skin swabs and blood samples from pets of people with mpox from 21 households. They sampled 24 dogs, 9 cats and 1 rabbit, obtaining a total of 191 swabs from animals and 56 swabs from the animals’ environments (e.g. beds, bedding, toys, bowls). The results were interesting:

  • MPXV DNA was identified by PCR from five animals (4 dogs, 1 cat) from 4 households. Two positive dogs were from the same household. That’s an overall positivity rate of 17% in dogs and 11% in cats sampled.
  • Multiple positive results were obtained from all of the positive animals. Overall, 12% (22/191) of animal samples were positive.

Breaking it down by body site, positives were from:

  • 29% (4/14) of skin lesion samples
  • 16% (6/37) of ventral skin/fur (stomach) samples
  • 12% (4/33) of dorsal fur (back) samples
  • 11% (4/35) of periocular (around the eyes) samples
  • 8% (3/36) of anorectal (butt) samples
  • 3% (1/36) of oral samples

Researchers also tested for RNase-P as an indicator of human DNA contamination, and all PCR-positive samples were also positive for RNase-P. While that doesn’t mean that the MPXV DNA all came from direct human contamination, it means there was evidence of human contact with the same sites at the same time.

Seven animals had skin lesions, but five of those had skin lesions before the owner got sick, so those cases were likely unrelated. Two pets developed skin lesions after the owner got sick (or at least no one noticed them before that) and both were PCR-negative for MPXV.

Twenty-nine percent (29%) of households had positive animal-associated environmental samples (e.g. dog beds, toys, bowls). All households with positive animals had positive environmental sites, but so did two households without positive animals. Environmental samples are always hard to assess in situations like this, because a positive result could be from contamination from the person or the pet. Environmental samples also don’t tell us risk, since PCR testing will also detect dead virus. It’s more of an indicator of the viral load in the area, and provides some suggestions of contamination routes and what sites might potentially be of concern.

PCR is a really sensitive testing method that can pick up even small bits of dead virus, so the researchers also followed up with viral culture, which is more time consuming, specialized and hazardous, while also being less sensitive – which is why it’s not typically uses it for initial testing. Culture is useful for figuring out if there truly was an active infection, because it only detects live virus. All PCR-positive samples in this study were negative on culture. That’s a bit hard to interpret with confidence.

  • It could mean that infection levels were low, since culture isn’t sensitive.
  • If sampling was done late in infection (which would be common in studies like this, since researchers can’t usually get into households really quickly, then active infection may have waned by the time of sampling.
  • It could be that samples didn’t pick up much virus.
  • It could also mean that PCR-positives were from contamination with dead virus.

Testing for MPXV antibodies in the blood was also performed in 20 dogs at the time of the first site visit, and all were negative. More importantly, 22 dogs were tested 3-4 months later and still had no detectable antibodies. That’s more important because initial negative results might just be because the body hadn’t yet produced detectable antibodies to the virus, but by 3-4 months, antibodies should be present if the animal was previously infected. It’s not a complete guarantee that the dogs weren’t infected, since we don’t know how good the antibody test is or how robust antibody production might be if infection was mild and transient. However, it provides more evidence that PCR-positive results could be due to contamination or a very low (and maybe irrelevant) level of transient infection.

Does this mean dogs and cats can or cannot be infected with MPXV by infected owners?

What this shows is that pets are definitely being exposed from their owners (not surprising) and that it’s possible that some are getting infected. However, it’s unclear whether these were true infections, and even if they were true infections, the low viral load and lack of clear mpox lesions would suggest that the transmission risk posed by pets is probably very low to negligible.

We still need more studies to learn about transmission of this virus to animals. If human-to-pet infection is possible but uncommon, a study of this size might not detect it. Nonetheless it was a great start, and people may underestimate the amount of work that no doubt went into it. My tentative assessment would be that clinically relevant MPXV transmission to pets is uncommon, the health risks to pets from owners with mpox is probably very low, and the risk from exposed pets is close to negligible. But I want more data before I get too confident in that assessment.

What are the challenges with this type of work?

Timely recruitment is a big challenge, because the pet needs to be sampled around the time of active human infection. That means someone has to develop mpox, find out about the study, contact the study team, and then someone needs to go to the household to collect samples, all in a pretty short period of time. For our study, the household also needs to be in close proximity to where we’re based, since I don’t have the budget to fly across the country to get samples. We sometimes get assistance from veterinarians for surveillance studies, but we don’t want infected people taking potentially infected animals into clinics just for sampling, as that creates transmission risks that are hard to justify (versus a person going to the house to collect the samples, while wearing all the appropriate personal protective equipment, of course). So these studies largely rely on active, in-household sampling.

What should be done with pets in households with people who have mpox?

It’s still wise to assume that human-to-pet transmission of MPXV can occur, and therefore take reasonable infection control precautions. The paper sums it up quite reasonably:

  • “More work is needed to determine the susceptibility of companion animals to clade-IIb MPXV. Thus, CDC still recommends that companion animal owners with mpox limit their interactions with their pets while infectious, particularly if they are sharing smaller living spaces. That precautionary measure is recommended until more information is available about the susceptibility of common mammalian companion animal species to mpox.
  • In conclusion, no strong evidence yet exists to suggest that common companion animals, such as dogs or cats, are susceptible to infection with clade IIb MPXV. Given high likelihood for exposure among most of these animals, the paucity of evidence indicating infection might indicate resistance to infection. Nonetheless, to prevent further viral spread and potential evolution and establishment of new endemic areas, during public health emergencies caused by emerging zoonotic diseases, responders should apply a One Health approach to investigate potential spillback of human infections to animals, including pets.”

There is one other important factor to consider: the MPXV strain we’ve been dealing with in humans outside Africa since 2022 is clade II. There recent increase in cases in Africa includes the more transmissible clade Ib virus. The original clade I virus still predominates, but if this more transmissible clade Ib continues to increase in people, there will be more opportunities for it spread outside Africa, and more opportunities for exposure of other animals, including pets. Time will tell whether that becomes and issue; if it does, we’ll need to repeat some research, since we can’t assume clade Ib and clade II have the same risk of infection of animals.

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The Colorado Department of Public Health and Environment recently released information about 6 cats in the state diagnosed with H5N1 influenza. Some aspects of these cases are totally unsurprising, others raise a lot of questions.

Colorado has been hit hard by H5N1 in dairy cattle, with over 50 herds affected since the spring, but they’ve also taken a more proactive response than many areas. This report covers the 6 cats that have been identified (so far) in 2024.

Let’s start with the totally unsurprising.

One cat was from an infected dairy farm.

  • Duh. That one’s easy to explain.

Three were “known indoor/outdoor cats that hunted mice and/or small birds as prey and also spent time indoors with their owners.”

  • These aren’t too surprising either. When the virus is circulating in birds, species that prey on birds are likely to get exposed.
  • Genomic evaluation of the virus will help tell us if the strains in these cats are consistent with those circulating in local birds (as they should be), versus the slightly different strains circulating in cattle (hopefully not).

Now to the unexpected cases. These are the most interesting and important cases, and they illustrate some major gaps in our understanding and approach to this virus.

Two cats were indoor cats with no known exposure to H5N1.

  • These cats didn’t have contact with birds or dairy cattle.
  • Presumably they also didn’t have contact with any person known to have had H5N1 (as there are still few enough of those cases) or contact with high risk people like dairy or poultry farm workers, but that’s not explicitly stated.
  • I also presume the authorities took a good enough history to make sure “indoor” really meant “indoor,” since “indoor” is sometimes an aspiration for cats, not a lifestyle. (Veterinarians are all too familiar with “indoor” cats that have been hit by a car or gotten into a fight with some kind of wildlife.)

So how did two “indoor” cats get exposed to the H5N1 virus?

A few potential, but still unlikely, possibilities come to mind:

  • Close contact with aerosols from infected birds or bird feces through window screens?
  • Close contact with aerosols from infected mammals (e.g. other cats) through window screens?
  • Birds that snuck into the house?
  • Unidentified infected humans?
  • Contaminated material from outside tracked in on someone’s shoes or clothes?
  • Raw food? (Including possibly raw milk?)

The latter, in the form of raw diets, has been shown to be a risk factor in a few outbreaks in cats, so we can’t dismiss it. However, the odds of a raw diet containing meat from an infected bird in Colorado are really low. So, I think potential causes are still wide open at this point. Genomic analysis should help determine if the virus from these cats is most consistent with the strain in dairy cattle or circulating avian strains.

These cases also highlight something else: surveillance bias. If you don’t test, you don’t find. If testing is focused (or restricted to) cats with known high risk contacts, we can get into a self-fulfilling prophecy of “cats only get infected if they have risk factor X.” The two unexpected cases in indoor cats show that we might need to throw a wider surveillance net, both to find more infected cats and to understand how this virus is being spread.

The disease presentation is also important. Five of the six cats had “an initial complaint of lethargy and inappetence, followed by progressive respiratory signs in some and fairly consistent progressive neurologic signs in most.” It’s not clear how disease progressed in the sixth cat, or if it was perhaps found dead. Consider that if testing focuses on cats with neurological disease, we’ll bias ourselves to thinking that this virus always causes neurological disease. I’m not sure at this point whether H5N1 infection usually causes serious neurological disease or whether the cats with serious neurological disease are just the small subset that we test for H5N1. If those are the only cats we test (perhaps as a secondary test when the cat was a rabies suspect and has tested negative for that virus first), then we’re not going to understand the true picture.

We need better and broader surveillance. I get worried when the focus of testing is on a narrow population. Yes, it’s lower yield to test outside those known high risk groups, but when we have lots of knowledge gaps, we sometimes have to go on fishing expeditions.

What does this tell us?

  • If H5N1 is in birds or cattle, cats can get exposed.
  • H5N1 can cause serious neurological disease in cats. Maybe that occurs in a minority of infected cats, or maybe it occurs in most. We just don’t know yet.
  • Not all cats with H5N1 will have known exposure to infected dairy cattle or birds. We need to do more testing to figure out what’s happening.
  • Infections in cats seem to be rare, but can be fatal, so we need to pay attention.

The risk posed by cats to people and other animals is completely unclear at this time. Some earlier data suggested that cats could have pretty high viral loads in respiratory secretions, so I think we have to assume that infected cats pose some transmission risk. That doesn’t mean we should panic or not try to treat them, but we should make sure we use good infection control practices around suspected and confirmed cases.

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This is really good news – albeit a bit frustrating that we spent so much time working on the issue over the last couple of months, only to have the US CDC largely walk back most of what they announced with regard to movement of dogs from low-risk countries for dog rabies back in May, and specifically dogs from Canada just last week.

The US CDC has once again revised the rules for importation of dogs into the US from dog-rabies free or low risk countries (including Canada) that will come into effect on August 1, 2024. This applies to dogs that have not visited any high-risk countries for at least 6 months prior to travelling to the US.

It’s quite simple, logical and straightforward now:

  • The dog owner (or whoever is accompanying the dog) must complete the new online CDC Dog Import Form for each dog. The form no longer requires a photo for such a dog, and is valid for up to 6 months, as long as the dog does not visit any high-risk countries. There is no fee or waiting period associated with completing this form (free). A separate form must be completed for each dog.
  • The dog must appear healthy upon arrival (this is not new).
  • The dog must be at least 6 months old at time of entry to the US.
  • The dog must have a microchip that can be detected with a universal scanner to identify them.

Notably, there is no longer any requirement for proof of rabies vaccination for dogs travelling from low-risk countries, but remember that proof of current rabies vaccination is still required for dogs returning to Canada from the US.

There is no apparent mechanism for verifying that the dog has not visited any high-risk countries for at least 6 months prior to travelling to the US, beyond the owner attestation on the CDC Dog Import Form. Dogs still have to be at least 6 months old, which will still be a potential issue for breeders and for cross-border veterinary care, but these changes remove most of the major challenges and hassles with which we’ve been grappling since the CDC’s original announcement in May.

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UPDATE: Shortly after this was posted, the US CDC walked back most of the requirements discussed below. This post will be left up for the historical record, but please note that the information no longer applies. Updated information was posted on July 22, 2024.

Here’s our current list of frequently asked questions about the impending changes to US dog importation rules, which was compiled in collaboration with the CVMA and CFIA. This is where we stand as of today, but as with any emerging situation, things may still change, so keep checking the CFIA website on dogs travelling to the US for the latest updates.

1) Will there be any exceptions or exemptions to the new rules?

These new requirements are set by the CDC, so if a derogation (exemption) is needed, the dog owner/exporter will need to contact the CDC directly to  request the exemption. It is at the CDC’s discretion to issue a derogation. This would most likely only be granted for dogs that must travel for veterinary care, but it should not be assumed that any derogation request will be granted, especially if it’s for any other reason. Derogation requests should be directed to CDC by phone (1-800-232-4636) or email (cdcanimalimports@cdc.gov). The CFIA does not have a role in this process. Owners should obtain any derogation in writing, as it should accompany the dog’s export documents and be presented when cross the border.

2) Have the new rules now been finalized?

Not necessarily. Discussions about the new rules and time frame for implementation continue. However, it is prudent to make plans based on the current guidelines as there is also no assurance that anything will change further.

3) What should be done with a dog that has a microchip that it is not ISO-certified?

Microchips that are universally readable but not ISO-certified can be used to identify the dog. However, if the microchip reader used at the border can’t read the microchip, the dog can be denied entry, so consider implanting a new ISO-certified microchip in cases like this, out of abundance of caution. CVMA maintains a list of ISO-certified devices.

4) What is considered “adequate” rabies vaccination?

Vaccination must be performed in Canada with a vaccine licensed for use in Canada. The Documentation of Canadian-Issued Rabies Vaccination form (the export document found on the CFIA’s webpage) indicates the following requirements:

  • A primary rabies vaccine which was administered on or after 12 weeks (84 days) of age AND at least 28 days have elapsed since vaccination.

OR

  •  A booster rabies vaccine which was administered on or after 64 weeks (15 months) of age and the owner had proof of at least 1 previous rabies vaccination that was administered on or after 12 weeks (84 days) of age.

5) For how long is a rabies vaccine considered valid if the dog was late getting its booster?

This is currently a grey area that on which we are trying to get clarification. This is not addressed on the Documentation of Canadian-Issued Rabies Vaccination form (the export document found on the CFIA’s webpage). There is no specific statement that boosters must be given as per label instructions. However, there can be debate about whether an overdue vaccine is considered a “booster” or a primary vaccine from a regulatory standpoint. To be safe, always aim to vaccinate within the vaccine label’s 1 or 3 year interval. The CDC takes a strict line on this in the US – overdue by 1 day means a rabies vaccine can only be considered protective for 1 year. So until we hear otherwise, out of an abundance of caution, if a booster is late, the vaccine should be considered a primary vaccine dose, which means:

  • it needs to be given 28 days prior to travel
  • it would be considered protective for only 1 year.

If there are concerns or hesitancy surrounding re-vaccinating dogs, then it may be best to wait until all the details about this particular issues have been finalized.

It is important to note that the Documentation of Canadian-Issued Rabies Vaccination form (the export document found on the CFIA’s webpage) is to be signed and authorized 28 days or more after the date of the primary vaccination AND the dog cannot enter the US until 28 days or more after the primary vaccine. This 28 day waiting period does not apply for booster vaccination given withing the prescribed interval (1 or 3 years).

6) If a dog is vaccinated against rabies but does not have a microchip, once the microchip is implanted, does the dog need to restart its rabies vaccinations?

Currently, we have to attest that the animal has a microchip and that it is properly vaccinated against rabies, not the order in which those things happened. There is no guidance on the Documentation of Canadian-Issued Rabies Vaccination form (the export document found on the CFIA’s webpage) that indicates microchipping must precede vaccination. However, in the US, dogs must be microchipped prior to vaccination, and any vaccines that are given before microchipping are not considered when evaluating rabies vaccination status.

Similar to the issue with overdue vaccines, until the rules are clarified, it is prudent to only consider rabies vaccines given after microchipping as valid for export to the US. Therefore, if a dog was vaccinated prior to microchipping, then revaccinate the dog after microchipping (or on the same day as microchipping). That dose of vaccine would likely be considered a primary dose, therefore requiring a 28 day wait until it is considered protective and would only be valid for 1 year. As there is conflicting information being reported in the US about how to approach re-vaccination after microchipping, we are hoping to get clarification on whether this very conservative approach will be necessary. If there are concerns or hesitancy surrounding re-vaccinating dogs, then it may be best to wait until all details about this particular issue have been finalized.

7) What records need to be provided for a dog that has been microchipped for less than 6 months?

If the dog has been microchipped for less than 6 months at the time of travel, two (2) veterinary records (instead of just one) must be attached to the Documentation of Canadian-Issued Rabies Vaccination form (the export document found on the CFIA’s webpage):

  • one that provides a description of the dog from 6-12 months ago AND
  • one that includes the same description, as well as the new microchip number. This is to provide assurance that you believe the dog with the microchip is the same dog for which you are providing the earlier record.  

8) What should be indicated in the medical record if a second microchip is implanted in the dog?

Both microchip numbers should be included in the medical record and on the Documentation of Canadian-Issued Rabies Vaccination form (the export document found on the CFIA’s webpage), so that there is no confusion if the original microchip is identified by the microchip reader at the border.

9) What veterinary records are required for a dog to cross the border to the US from Canada?

A veterinary record from between 6-12 months prior to travel is required as part of the process to confirm the dog has been in Canada for at least 6 months. This is described in note 4 on the Documentation of Canadian-Issued Rabies Vaccination form (the export document found on the CFIA’s webpage). This can be anything that documents the dog, its microchip number and contact with your clinic or another Canadian veterinary clinic. Examples of an applicable Canadian veterinary record include vaccination certificate, health certificate, invoice or purchase record (e.g pet food purchase, prescription renewal) from the veterinary clinic. The dog’s complete medical record in not required. While a record of a clinic visit during which you examined the dog is ideal, it appears that any clinic record for the dog would qualify, even if there was no associated examination or direct contact with the dog itself.

10) What should be done if a dog was last seen 15 months ago for vaccination and there are no veterinary records documenting contact with the dog in the past 6-12 months?

If records from the past 6-12 months are not available, the dog is not eligible to enter the US.  They would have to wait 6 months, but not more than 12 months, from their latest visit. The importance of a yearly veterinary visit should be emphasized to owners who may want to take their dogs to the US. This is also an opportunity to discuss travel-associated disease risks and preventive medicine that may be relevant to the dog based on the intended destination (e.g. vaccination for other regionally prevalent diseases, tick prevention, heartworm prevention).

11) What should be done if a dog was last seen 15 months ago for vaccination, and then again 3 months ago, but there are no records in between during the 6-12 month interval from the date of travel?

As above, a record of some kind from 6-12 months ago is required. If that is not available, the dog would have to wait another 3 months until its last visit falls within this interval.

12) What should be done with a new patient being seen for the first time, that has valid vaccination and medical records, including a veterinary visit from 6-12 months ago, but not from my clinic?

The owners can use records from the other Canadian veterinary clinics to document the dog’s status. You can fill in the Documentation of Canadian-Issued Rabies Vaccination form (the export document found on the CFIA’s webpage) and the records from the other clinic can be used to document the dog’s history in Canada.

13) What are the options for a new patient that was microchipped and vaccinated at another clinic in Canada but the owner cannot get medical records?

The dog must have a medical record from 6-12 months earlier to show that it has been in Canada for that time period. If the owner cannot get the previous records, the dog must wait until that time frame has been reestablished based on records from the new clinic. Re-vaccination will also be required if the previous vaccination record cannot be found. The new vaccine would be considered a primary dose and therefore not protective until 28 days after vaccination, and only valid for 1 year.

14) What happens with a dog that moved to Canada from France with its owners 3 months ago, that the owners now want to take to the US?

Currently, dogs from other countries must be in Canada for at least 6 months, or they must travel directly to the US from their original country of origin. If a dog has moved to Canada within the past 6 months, it must be vaccinated in Canada and reside in Canada for 6 months before it is eligible to be taken to the US directly from Canada.

15) Can an exemption be made, or can a rabies antibody titre be used in lieu of re-vaccination, if an owner does not want to re-vaccinate their dog?

The requirement is current vaccination against rabies. There is no option to use an antibody titre in lieu of a rabies vaccination. If there are contraindications to vaccination for a particular dog, a letter to that effect can be provided by the veterinarian to CDC as part of the owner’s derogation request. Demonstrating an acceptable titre might be useful as part of the derogation request. The likelihood of acceptance of such a request is unknown.

It is also important for clients to be aware that, even if they get a CDC derogation, there may be individual state requirements for rabies vaccination of dogs, and that rabies vaccination is required if the dog is to return to Canada.

16) Can a medical exemption be obtained for a patient that would go straight from a Canadian veterinary clinic to a US veterinary clinic and back?

No, not beyond the standard derogation process mentioned above. A derogation is probably most likely to be granted for a situation like this, but is not guaranteed, and it would not necessarily be granted quickly. Last-minute border crossing for veterinary care may not be possible for dogs that are not able to immediately fulfill the standard requirements.

17) What should be entered on the export form if the date the dog’s microchip was implanted is unknown?

You can enter the date that you first documented the dog’s microchip in your medical records.

18) Can a veterinarian sign the export paperwork for their own dog?

This is not specifically addressed in the new rule, but it is a standard best practice for veterinarians not to sign export papers of any sort for their own animals, because of the potential conflict of interest. If possible, another veterinarian should sign the paperwork. If that is not possible, it would be wise to contact CDC to see if this will cause any problems.

19) What destination address should be entered for clients who are taking their dog to a park, mall or some other location in the US that’s not a house or hotel?

The address of a park, shopping facility or other location can be indicated as the destination. If multiple places will be visited, the location that the dog will spend the most time should be used. It must be an actual address (i.e., not a PO box). The US address being visited may change from what is initially recorded on the Documentation of Canadian-Issued Rabies Vaccination form (the export document found on the CFIA’s webpage), as it’s valid for up to 1 to 3 years. However, the dog owner/exporter will also complete the CDC’s Dog Import Form for each entry into the U.S., and there they will indicate the current address they will be visiting.

20) Can the export form be completed in French?

No, as the form is for submission to US officials, it must be completed in English. However, we are still awaiting confirmation that the accompanying medical records that are being used to document the presence of the dog in Canada can  be supplied in French, as long as the dog’s name, owner’s information and microchip ID are clearly identifiable.

Where is the most up-to-date information on movement of dogs from Canada to the US posted?

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Our oversubscribed CVMA webinar on the new US dog importation rules coming into effect on August 1 showed just how many questions are still out there about the changes. An FAQ is in the works that will help address many of these, so stay tuned for that.

The topic of this post is: why are they making these changes in the first place?

The current focus of most questions is obviously on the “what,” but I also get a lot of questions about “why.” I’m not sure there’s a great answer to that, but below are a few of the issues influencing the decisions.

Is importation of potentially rabid dogs into the US really an issue that needs to be addressed, especially in what seems like such a rushed manner?

Rabies is a big deal, no doubt about it. It’s estimated that about 50,000 people die of rabies every year internationally, the vast majority from canine rabies virus variants in places where the virus in endemic in feral dogs. It’s an almost invariably fatal disease, but it’s almost completely preventable even after exposure with prompt post-exposure prophylaxis. This makes it an interesting combination of a horrible but controllable disease – at least in areas where post-exposure prophylaxis is available and when people know they need to get it (those are usually the weak links everywhere).

Okay, rabies is a big deal. But is importation of rabies in dogs from places like Canada something that needs to be addressed?

Kind of. It’s been estimated that upwards of 1 million dogs travel from Canada to the US every year, but canine rabies virus variants (i.e. strains that spread within in the dog population) are not present in Canada. Dogs in Canada can get definitely get rabies, but this is usually from exposure to wildlife rabies virus variants that circulate in reservoir species like skunks, raccoons, foxes and bats. Overall, spillover infections like this causing rabies in dogs in Canada are rare, due to a combination of limited exposure of dogs to rabid animals (thanks to rabies wildlife control efforts) and some level of vaccine coverage in the dog population. The risk of rabies in dogs can be higher in some areas like northern communities where there is more exposure to reservoir wildlife species and less access to rabies vaccination for dogs. In 2023, there were three confirmed cases of rabies in dogs in Canada; two dogs from Nunavut and one from the Northwest Territories. So far in 2024, one dog in Manitoba has been confirmed to have had rabies.

So, we don’t have much risk from Canadian dogs, and realistically the risk is no greater than from any US dog. The concern is mainly around dogs imported from high-risk countries where canine rabies virus variant is circulating, including dogs that may be imported into Canada and then travel to the US. That’s a reasonable concern, but Canada also has reasonable controls to reduce the risk of importing rabid dogs (not great, but they’re getting better), so the risk of a rabid dog getting into Canada is pretty low, although two such incidents have occurred recently (both rabid dogs were imported into Ontario in 2021). Unfortunately, a massive number of exceptionally low risk dogs get caught up in measures that are very much erring on the side of caution, and are really just trying to address a few bad actors who try to skirt the rules and end up putting people and animals at risk.

Why won’t they allow importation of puppies less than 6 months of age?

Canada has pretty good controls on importation of puppies for commercial purposes (which includes resale and adoption), and on all dogs from countries that are high-risk for canine rabies (which were banned as of September 28, 2022). Unfortunately high-risk puppies can still cross the border as personal pets, all too often even when they’re not (e.g. rescue dogs for adoption, which should be classified as commercial). So, there’s no guarantee that a puppy in Canada didn’t just get off a plane from somewhere else and where it might have been exposed to rabies.

The question then becomes whether the US CDC can trust a Canadian veterinarian to attest that a puppy was born in Canada to a dog that is under their care. Yes, it requires some trust, but presumably a veterinarian falsifying such an attestation would suffer some pretty major repercussions, so it’s hard to imagine this would be a big risk. Remember: we should be aiming for maximum risk reduction, but that rarely equates to risk elimination. No protocol can 100% guarantee a rabid dog will never be imported into any country.

Why does there now need to be proof the dog has been in Canada for at least 6 months?

This is based on the assumption that if a dog came in from a high-risk country and was already infected with rabies, it would develop clinical signs (and die) within 6 months. That’s quite reasonable and is a well-accepted time period for incubation of rabies in dogs internationally, but even that is not a guarantee. In 2021, a dog was imported into Ontario from Iran that took just over 6 months to develop signs of rabies, but this was a very exceptional case. The 6-month time period also does nothing to address the risk of exposure to endemic wildlife rabies in Canada, from contact with skunks, foxes, raccoons or bats.

So, the 6-month limitation is largely to prevent “laundering” of high risk dogs through Canada, whereby they could otherwise arrive in Canada from a high-risk country an then shortly thereafter be moved to the US without disclosing the real country of origin. Fraudulent importation paperwork has been an increasing issue with dogs coming into the US, so the new approach brings in another level of scrutiny, as a veterinarian has to be involved in the process for at least 6 months. But what percentage of the risk from the million-ish dogs that cross the border each year would this really address? An exceptionally small one. Unfortunately, measures like these often get put in place to address uncommon or rare high-risk situations, and mostly end of causing problems for everyone else.

Does the 6-month requirement make sense?

The concept makes sense. The execution could be improved, since there are some major hassles with the current approach. If a dog doesn’t have a veterinary exam or other contact with a veterinary clinic documented in the 6-12 months before it is supposed to leave for the US, it can’t go. Even dogs that consistently visit the veterinarian every year would have large blocks on time when they couldn’t fulfill those requirements.  Some practical measures to improve the implementation could include extending the window beyond 6-12 months, and/or providing veterinarians with leeway to attest to the dog’s presence in Canada if they are confident about it, even if there’s no official record during the prescribed period.

Why is it a big deal if we import a rabid dog every once in a while?

That’s a fair question. There are lots of other diseases that impact people and animals, some of which can also transmitted from dogs. Rabies doesn’t crack the top 100 list of things that kill people or dogs in Canada or the US. Although I’d never dismiss the importance of rabies, we have to think of the cost-benefit for measures meant to address an exceptionally rare problem, that is importation of an infected dog into Canada with subsequent movement of the dog to the US within 6 months, and then transmission of rabies from that dog to people or other animals. These extensive measures, in terms of their application to dogs from Canada (vs dogs from high risk countries), address an exceptionally small subset of that problem. Focusing on proof of vaccination could be less disruptive and just as useful. It’s still no guarantee that rabid dogs won’t get across the border, because a dog can be vaccinated after it was exposed and still develop rabies, but once again we’re getting into very rare hypothetical situations.

The worst case scenario is that someone dies from rabies that they got from an imported dog. There’s also theoretically a risk to the population, if a rabid imported dog started a chain of transmission that led to canine rabies virus variant re-establishing itself in North America. That is very unlikely to happen, because it would require a large pool of unvaccinated dogs (or other canids) in reasonably close contact (i.e. high density) to maintain transmission. The infected dog would need to infect at least one other dog during the relatively short period that they are infectious before they die (usually 1-2 weeks). Since we don’t have a large population of feral dogs, have reasonable vaccine coverage in pet dogs, and have the resources to intervene aggressively to prevent spread (e.g. point-control vaccination response for wild and domestic canids), the odds of canine rabies re-establishing itself in dogs in Canada or the US are approaching negligible.

  • We can’t be quite as confident about avoiding canine rabies becoming established in wildlife in North America, but the risk is still really low. If an imported dog transmitted rabies to a wild canid (e.g. coyote), that canid would then need to pass it on to other canids. The host range and dynamics of canine rabies virus variant in other, non-domestic canids isn’t well understood. For example, there’s debate about the role of species like jackals in rabies virus transmission in Africa. It’s been suggested that the canine rabies virus that circulates in jackals only does so because there’s continued spillover from feral dogs. If there were no infected dogs, the virus would die out in jackals. If there was rare introduction of rabies from dogs into our wild canids, it’s pretty unlikely (though not impossible) that we’d see establishment of the new variant in wildlife. I’d rather avoid testing that theory, but it’s probably not a very realistic concern.

So why are they making such a big deal about this?

There are major direct impacts of exposure to a very limited pool of people and domestic animals from an imported rabid dog. That’s not inconsequential. It can take a lot of time and money to address cases like that, they cause a lot of stress for a lot of people, and if they’re not recognized and managed properly, they can result in devastating infections.

What about cats? They get rabies too.

There actually tend to be more rabid cats than dogs each year in Canada and the US, but globally dogs are the main concern. There’s no feline rabies virus variant, they are only infected through spillover transmission from other species. Nonetheless, cats are an important source of human infection. Is the risk of rabies from 10,000 imported dogs compared to 10,000 imported cats from the same region actually is probably higher in dogs, since the virus circulates more readily in dogs, but it’s certainly not a no-risk situation with the cats either.  The main difference in risk is probably the fact that we import substantially larger numbers of dogs. It’s not that cats pose no risk, they just pose less risk.

Do all these new measures make sense?

Yes and no. Rabies is a big deal. It’s rare in dogs in North America, but a single case causes a lot of problems and results in a lot of time and expense. There are legitimate concerns about importation of rabies in dogs.

But a lot of time and money is being burned and a lot of hassles are being created to address a rare problem (if that problem even exists). We have lots of human and animal disease issues. Is the time and effort spent on this issue a good investment? Probably not, at least not to the degree that’s required to implement these changes.

Canada’s Health Minister Mark Holland made a statement about the new requirements, in which he said, “Frankly, I just don’t think this is a good use of border officers’ time. There’s a lot of issues at the border. Whether or not my Maltese is another Maltese and having a border officer figure that out, I’ve said to [U.S. Health Secretary Xavier Becerra], doesn’t make sense to me.”

I’m not saying the new approach is useless. Some of the principles make sense, and tightening up some rules and loopholes is logical. However, it’s currently an overly cumbersome approach that brings in some complicated measures that don’t add a lot of value when it comes to applying them to dogs from Canada in particular, and many potential issues and unintended consequences are being encountered.