Issues about infectious disease risks from the pretty much totally unregulated importation of dogs continue to rise, and I’m dealing with them in one way or another almost daily at the moment. I’ll stay away from the discussion of what we are and aren’t (mostly the latter) doing in Canada, since I’ve covered that before.
What I want to write about now is a push in New Zealand to ban entry of dogs carrying methicillin-resistant (MR) staphylococci, including MRSA and MRSP.
The push makes sense at some levels:
- MR staph infections are a problem
- MR staph are currently rare in pets in New Zealand
- We can find the same strains of MR staph in animals multiple countries, suggesting they do travel from place to place
- Prevention is better than treatment
However, it’s not that clear cut. One issue relates to the standard line “all staph are not created alike”. Methicillin-resistance is common in a wide range of staph species carried by perfectly healthy animals. Many of those species are of little to no risk to people or animals.
A related issue is how MR staph get into a dog population. There are a few main ways. One is from humans – MRSA and other MR-staph are present in people, and most MRSA in pets is human-associated. So unless there’s a parallel extermination of these bugs in humans in New Zealand (a rather unlikely scenario), there’s an ongoing risk of exposure of native dogs.
Another snag is transmission of methicillin-resistance from common resident staph species to species that cause disease. While MR-staph infections may be very rarely identified in the country, it’s very unlikely that there are no MR-staph of any sort in New Zealand. I’d wager that I could find MR-staph of various sorts in New Zealand dogs, so this risk would remain even if dogs being imported were restricted.
Feasibility and practicality are other concerns. Yes, dogs could be tested and held at the border or in a quarantine facility awaiting results, but what would be tested, and how? How the testing is performed (e.g. what samples are collected and what lab methods are used) can have a major impact on the results. We don’t actually know how to confidently declare a dog to be free of MR-staph. If I had to make a recommendation now, it would be to take swabs of the nose, throat, rectum, skin and area around the hind end (perineum), and test each swab using an enrichment culture method. Since the two main staph of concern, MRSP and MRSA, behave differently in the lab, two different approaches would be required. Further, I wouldn’t have complete confidence in one round of testing, so I would probably want that done at least twice. It’s possible but it wouldn’t be cheap or easy… and you still won’t get me to sign anything saying this will "guarantee" that a dog is free of MR-staph.
Ultimately, trying to prevent entry of MR-staph is rather futile, and it also doesn’t address the bigger issues, such as how antibiotics are used, infection control practices and other components of veterinary care that influence the spread of MR-staph. While I applaud the fact that they’re being proactive by thinking about ways to control these bugs, and that they’re paying attention to importation, import controls aren’t going to be a great tool for MR-staph control. Paying attention to judicious use of antibiotics, use of common-sense hygiene practices in households, improvement in infection control practices in veterinary hospitals, and good basic veterinary care for pets would be much more effective.