Most people don’t realize the massive number of dogs that are imported into Canada every year, for all kinds of reasons: from people moving with their own pet, to importation of large shipments of dogs from puppy mills or rescues (the latter ranging from really good operations to really dodgy). Moving animals (or people) from one place to another always creates some degree of risk of moving diseases along with them, but there are things that we can do to reduce that risk. Vaccination is one of those things.

Rabies vaccination is a pretty standard requirement for international movement of dogs into many countries. In Canada, we require (kind of) vaccination of dogs that are entering the country. (I say “kind of” because in practice an unvaccinated dog coming as a personal pet may be permitted to enter Canada with a promise to get it vaccinated within a few weeks.) The vaccination requirement hopefully helps reduce (but does not eliminated) the risk of a rabid dog being imported, and, just as importantly, helps ensure that dogs that arrive are protected from exposure to rabies in Canada, where we have endemic rabies in bats and some terrestrial mammals. 

This vaccination requirement is not a guarantee that rabid dogs won’t be imported, though. The last two rabid dogs in Ontario were imported dogs, and both had a history of rabies vaccination. Most rabies vaccines are really good, but still not 100%, and vaccine quality (especially in come other countries) and vaccine record veracity (i.e. did someone falsify the vaccination certificate) are also concerns. 

Dr. Catherine Belanger coordinated a recent study looking at rabies antibody titres in imported dogs. There is no established “protective” titre for rabies in dogs, but there’s an international standard of 0.5 IU/mL that’s used to indicate what we assume to be a proper response to vaccination. 

For this study, dogs that were being imported into Canada and arriving in Ontario were enrolled (not an easy task, especially during a pandemic).

• From October 2021 to November 2022, blood samples were collected from 67 dogs, mainly arriving from Egypt (46).
• Concerningly, almost half (32/67, 48%) had antibody levels below the 0.5 IU/mL cutoff, and 14% had no detectable titres at all (despite all dogs presumably having a rabies vaccination certificate to get through customs).

Whether the poor results are because of poor quality vaccines, problems with vaccine handling (e.g. degradation because of cold chain issues), falsified rabies vaccination information or poor response to the vaccine can’t be determined. Any or all are possible contributing factors. 

These results highlight concerns with rabies immunity in imported dogs. In Ontario, there’s a legal requirement for all dogs over 3 months of age to be vaccinated against rabies by a vet licensed in Canada or the US, with a vaccine licensed in Canada or the US. Many people don’t realize that means dogs imported to Ontario from places other than the US are considered unvaccinated and need to be vaccinated upon arrival, even if they were vaccinated abroad – but that only applies in Ontario. Canada allows dogs to enter based on vaccination in other countries and other provinces do not have the same requirement to re-vaccinate dogs for rabies on arrival. Even so, revaccination is a good general practice for imported dogs unless there’s very good confidence in the vaccination history. Titres can also be tested, but that’s more expensive than another vaccine, and rabies vaccines are very safe. 

Another interesting aspect of this study was the availability of pre-exportation rabies titres for a subset of 29 dogs from Egypt (from a rescue that puts in extra effort and tries to ensure dogs are protected before they leave).  

• All of those were reported to have a titre above the desired cutoff based on an ELISA test.
• However, upon arrival, 38% of them had titres less than 0.5 IU/mL based on the RFFIT.

The RFFIT is approved by the World Organization for Animal Health (WOAH). The ELISA that was used prior to importation is not, and the differences between the two test methodologies are important. There could have been a decrease in antibody levels between when the two tests were run, but there wasn’t much of an interval (median 7 days apart), so it’s more likely the tests themselves or lab issues that account for the different results. This highlights the challenges that exporters face even when they want to do the right thing by testing prior to shipping the dogs.

To try to put that 48% of dogs with a titre less than 0.5 IU/mL in perspective, a comparison was made to test results from non-imported dogs in Ontario that had rabies antibody titres tested for other reasons.

• 14% of non-imported dogs tested (9/65) had titres less than 0.5 IU/mL. That’s a lower proportion compared to the imported group, but still not great.

A more direct comparison was with 49 local dogs that were tested for export purposes, since they presumably were on a regular rabies vaccination schedule, and would be expected to have a good titre.

• Only 8% of dogs tested in Ontario for export purposes had titres less than 0.5 IU/mL.

Beyond the issue with imported dogs, the 14% of non-imported dogs with low titres is a concern, since that suggests we might already have a reasonable pool of dogs with poor titres here in Ontario. This highlights the importance of a proper response to potential rabies exposure. If a dog is potentially exposed to rabies, we want to give it a rabies vaccine booster within 7 days. Even if a dog has a suboptimal titre, if it’s been previously vaccinated, odds are probably quite good that it will have a strong response to the booster, meaning that while its initial antibody levels are low, its immune system will still be ready to go and can ramp up antibody production quickly, because of the previous vaccine(s). With a proper (and prompt) post-exposure response, we can still keep the risk of rabies in the dog very low.

While somewhat unsurprising, this study highlights various issues and challenges with imported dogs, and the need to scrutinize when and how we import them, and how to manage them after arrival.