I’ve been holding off on this post because the situation is still evolving, but there’s enough of a rumour mill developing (and I’m getting enough emails from concerned people) that I thought I should respond.
A little background:
- Brucella canis is a bacterium that can cause a variety of issues in dogs (particularly reproductive issues), and can also be transmitted to people.
- While it’s rare (well under 1%) in pet dogs in Canada and the US, it’s more common in dogs from commercial breeding operations (e.g. puppy mills) and dogs from certain parts of the world.
- We don’t see infections in dogs here very often. When we do, most of the time (but not always), it’s a dog that came from somewhere else.
- B. canis is hard to treat and it’s hard to have confidence that it’s been eliminated from the dog after treatment, even if visible signs of illness have resolved.
- It can also be spread to people. However, human infections seem to be rare and close, direct contact is likely required for transmission.
- The greatest human risk likely comes from contact with female dogs that have aborted or recently given birth (whelped), since the bacterium can be present in high numbers in fetal and reproductive fluids and tissues.
Current situation in Ontario:
It’s my fault, I guess, since we’ve started screening imported dogs for disease surveillance as part of a research project. If you don’t look, you don’t know. If you do look, sometimes you end up revealing a complicated situation.
It wouldn’t really be surprising to find B. canis in a small percentage of imported dogs, since foreign, intact (i.e. not neutered or spayed) dogs are a higher risk group for infection to start. So, it isn’t a shock that we have identified some suspected and presumptive cases in recently imported dogs. Diagnosis of B. canis infection isn’t always straightforward either, so it’s tough to be definitive at this stage.
Testing of healthy dogs involves use of a screening test (RSAT) to start. This type of test has a high sensitivity (it will pick up a very high percentage of infected dogs) but a lower specificity (some dogs that aren’t actually infected will test positive too, these are known as “false positives”). Dogs that are positive on the screening test are then tested again using other tests to try to confirm the diagnosis. So far we have one dog that was positive on the second test. We have some others that were positive only on the first screening test. That could be because there was a cross-reaction and they are actually false positives, or it could because they were only very recently infected, or because the follow up tests aren’t as sensitive. With that type of result, we consider them suspicious and typically recommend trying other tests or repeating the testing in a month or so.
Take home messages (at this point):
- 1 dog with B. canis infection is a concern but it’s not overly surprising. A lot of infected dogs would be more of a problem. We’re trying to sort out which scenario this is.
- With infectious diseases, it’s best to err on the side of being overly cautious at the start and take extra precautions initially, while things are being sorted out. Sometimes we look back and realize we didn’t need to do all those things based on the final result, but it’s better than not doing enough at the start and then trying to play catch-up later.
- The risk to the general dog population is very low. Close and direct contact with an infected dog is required for transmission to either other dogs or people.
- The current situation is likely lower risk than many other situations, such as people buying dogs that came from puppy mills or other imported dogs where no one is looking at their disease status at all.
- The groups with which we are working are taking a proactive approach to make sure problems don’t develop or spread.
- Knowing is better than not knowing, even if it sometimes causes confusion or concern at first.
More information will follow, and if there’s a significant risk to the broader dog or human population, I’m not one to hold back saying that. At this point, people shouldn’t worry. For more information on B. canis in dogs and the associated public health risks, a review of the topic was recently published in Emerging Infectious Diseases.