As per yesterday’s post, another rabid imported dog was identified in Ontario, again from Iran. What’s particularly surprising about this case is the very long incubation period. The dog didn’t develop signs of rabies until over 6 months after importation, and it was confirmed that it was infected with canine-variant rabies (consistent with strains circulating in Iran) so it was infected before it came to Canada. Even it this dog was exposed to rabies virus the day it left Iran, that’s a really long incubation period, and it highlights some of the challenges in controlling import-associated rabies.
It’s also led to more questions about how we can prevent rabies from being imported when we import dogs.
The answer is: We can’t. There’s no way to completely prevent importation of dogs that are infected with rabies (unless we stop importation of dogs altogether).
What about vaccination requirements?
- The main role of rabies vaccination requirements for imported dogs is to make sure dogs are protected from exposure to rabies here in Canada (where rabies is endemic in our wildlife). Vaccination prior to importation is good, for sure, but it doesn’t mean the dog has zero chance of carrying rabies upon arrival.
Why doesn’t rabies vaccination ensure that a dog isn’t rabid?
- Rabies can have long incubation period (as demonstrated by the latest imported case). If a vaccine is given to a dog that was already infected some time ago, odds are it’s still going to get rabies, but it may not happen until after it’s imported. (Pets that are exposed to rabies, whether previously vaccinated or not, should be given an additional dose of rabies vaccine as soon as possible as their best chance for preventing clinical disease. This is the same principal used in exposed people, who need to start post-exposure prophylaxis as soon as possible (ideally within a few days) after an exposure to prevent infection.)
- We can require dogs be to vaccinated a month before they arrive here (this is currently a requirement for puppies less than 8 months of age imported for adoption or resale), but this strategy is still designed to make sure the dogs are protected from rabies exposure upon arrival, not before.
What about testing dogs for rabies on arrival?
- The testing for rabies that’s used in Canada (which is the internationally accepted standard) involves testing brain tissue directly. That requires a dead dog, so it’s obviously not a viable import screening test.
- Even when testing is done, it just tells us whether rabies virus has made it to the brain. It takes time for rabies virus to make it from the site of exposure (which can be anywhere on the body) to the brain. Infection of the brain is pretty late in the process, so dogs that arrive carrying the virus wouldn’t have any evidence of rabies virus in the brain until later, just before (about 10 days) they get sick.
What about testing dogs for rabies antibodies (titre testing)?
- An antibody titre tells us that the body has responded to the virus or the vaccine. It doesn’t tell us whether the dog is infected or not.
- A negative antibody titre would suggest that the dog wasn’t actually vaccinated for rabies (or the vaccine wasn’t any good, or the dog didn’t respond well to the vaccine) and that would mean it’s at higher risk of getting rabies if it’s exposed. It doesn’t tell us whether the dog is already infected or not.
What about quarantining imported dogs?
- Well, that would work but it’s impractical. The internationally accepted incubation period for rabies in dogs is 6 months, so that’s how long the dogs would need to be quarantined. That’s expensive, logistically challenging and not good for dog welfare.
- However, even a 6-month quarantine won’t catch every case. The most recent rabid dog from Iran showed that. It was imported in June and didn’t show signs of rabies until January, meaning it would have had to have been quarantined for over 6 months to detect this infection.
So, what do we do?
That’s a tough question. If we import dogs from rabies endemic areas, we have risk.
The risk presumably goes up when:
- We know less about the dogs pre-import: Some imported dogs have more information about them than others. Dogs that were surrendered or from a facility where the health status is reasonably well know are lower risk. Dogs that have had rabies vaccination well in advance of importation are lower risk too, as that would help protect them from exposures pre-departure, but that’s uncommon. Not many dogs that make it into international import pathways are higher health status dogs with regular prior rabies vaccination (though there are some, like personal pets of individuals who have immigrated to Canada or returned from assignments overseas and could not bring their pets with them initially).
- Dogs are imported sooner after being caught/collected: Similar to knowing more of the dog’s history, the longer an animal is at a managed facility, the greater the chance of detecting problems like rabies before the dog is shipped to another country. We’d need months of quarantine pre-departure to have much assurance, but more time means lower risk, to some degree.
- There’s questionable vaccination status (false paperwork) or vaccine quality: Yes, va accination requirement isn’t anywhere close to perfect in terms of an imported rabies prevention tool, but it’s still useful and better than nothing (especially if there’s a required waiting period between vaccination and importation).
- Dogs are imported shortly after they are able to be vaccinated: The latest imported rabid dog was about 3 months old when it was imported, so it would only have been able to be vaccinated right before it left (12 weeks being the typical minimum age).
Ultimately, the main way to reduce the risk is to reduce the number of dogs that are imported from high risk areas. The US has banned importation from over 100 countries considered high-risk for canine rabies, and that’s resulted in some of those dogs being diverted to Canada.
I’m not saying we should ban importation of dogs. There are good and bad points about canine importation. However, we need to do it better.
- Importers need to be more diligent and transparent.
- Unscrupulous, unethical and just plain crappy importer groups need to be addressed.
- Importers need to ensure that adopters understand the risks (and that the risks can never be completely eliminated).
- Adopters need to be aware of the issues, be willing to accept the risks, and make sure potential problems are investigated so we don’t miss rabies or something else serious.
- Ultimately, tighter regulations will help with many aspects of importation, but more for a range of other health and welfare issues than rabies, unless Canada takes similar steps as the US and bans importation from higher risk areas.
Still, if we’re going to continue to import dogs from other countries (or even move dogs from high-risk regions of Canada, like the far north), we’ll have to accept some degree of risk and make sure we have measures in place to contain those risk, as much as is possible.