April 1, 2013
It was 2007 when canine geneticists threw us an unexpected bone. After spending years mapping the entire canine genome, they had encountered an unanticipated application for their findings. They'd make use of their accumulated knowledge to help tease out the true purebred provenance of even the motliest mutt.
These so-called “mutt tests,” officially termed “dog breed identification genetic tests,” were the very first of their breed. Which is probably why the results seemed a bit sketchy. And probably why so few of us bothered to try them.
As a blogger, however, I felt compelled to put these tests to the test. When I did, the results seemed head-slappingly silly. I mean, it was hard to look at a medium breed, short-nosed dog and consider the Chihuahua an acceptable answer to the question of black-box parentage.
It was this kind of seemingly off-the-wall answer that left dog owners feeling fleeced and the vet profession bewildered. Which is why, despite its sound scientific roots, the less charitably inclined took to renaming the “Wisdom Panel” the “witless panel.” (Ouch!)
But fast-forward five years and things are definitely looking up for these test makers. Over time, these tests have been continually refined for greater accuracy and precision, which only makes sense. After all, more purebred testing means more genetic markers and, ultimately, more believable results.
Now that doesn't mean the tests are perfect. And it certainly doesn't mean the results won't confound us at times. But with all this newfound credibility comes a greater willingness to re-examine all those F1-F2-F3 diagrams we left behind in vet school.
After all, when observed in light of the tremendous variability in canine phenotype within a startlingly stable genotype, it's no longer too taxing to imagine a pit bull-ish dog as progeny of a well-motivated Chihuahua. (It happens more often than we probably know.)
While I never doubted the fundamental science behind the tests, I confess to having once been a devout skeptic of their relevance. To paraphrase my first post on the subject: Who cares if it's a cocker spaniel, poodle, or Portuguese water dog? What difference does it make except to potentially perpetuate the notion that mixes are in need of definition and, by inference, that purebreds are preferable?
But now I believe I've been mistaken to disdain the utility of greater genetic certainty. After all, these tests are good for at least three things:
1. Accurately assessing the risk of specific genetic diseases can help us direct our diagnostic dollars.
2. Breed or breed class designations can help head off big behavior issues if we're better able to channel our patients' drives. With shelter death as a top killer, this factor might be more significant than you may initially think.
3. Despite the science supported by the American Veterinary Medical Association and the U.S. Centers for Disease Control and Prevention revealing no evidence of any breed's inherent propensity for violence, thousands of dogs are put to death every year for the sin of semi-resembling a specific breed a community deems problematic.
If accepted by courts and law enforcement as an acceptable means of breed identification, a high percentage of these dogs could escape exile or eradication.
Given all the above circumstances, understanding our mixed breed dogs' true parentage might well save some lives. But it's this last issue that especially impressed me after the publication of a commentary in JAVMA titled “Rethinking dog breed identification in veterinary practice.”
Its goal was simple but decidedly counter to common practices in veterinary hospitals throughout the United States. While most of us choose to assign a specific breed or breed mix to nearly every patient (in our medical records, for municipal licenses, travel documentation, etc.), the authors convincingly argued we should omit to ID in the case of mixed breed dogs whose parentage is unknown and, indeed, for all those whose purebred status is questionable.
Referencing canine genetic studies demonstrating that an offspring's phenotype varied dramatically from its immediate progenitors,' the authors agreed with genetic researchers who established that mixed breed dogs' genetic underpinnings could not be accurately deduced based on appearance alone.
This conclusion is in stark contrast to a conventional wisdom advancing the notion that a dog's purebred heritage can be readily discerned from its phenotype—an erroneous assumption we in the veterinary profession have done little to dispel. In fact, if anything, we've perpetuated it with speculations and conjectures preserved in legal documents since the dawn of our profession.
Which would be innocuous enough if our patients' very lives weren't depending on the application of the logic and reason our scientific schooling connotes.
After all, in my hometown of Miami, dogs die if they're assumed to be a pit bull mix instead of a bullmastiff, American bulldog, bull terrier, boxer or Boston terrier cross. Even my Chihuahua mix might have been subject to fines and untimely death if Animal Services officials had determined her looks to suggest a pit bull basis.
But it's not just breed bans we have to contend with. Homeowners' insurance policies and airlines are problematic here, too. Decades ago, carriers began adopting policy and flight exclusions for purebreds deemed violence-prone.
The uninsurable and no-fly lists included the usual suspects, such as German shepherds, Rottweilers and Dobermans, but were soon expanded to include breeds like boxers and English bulldogs, too. (Yes, at least one insurance carrier excludes all “bulldog” breeds.) Adding insult to injury, such exclusions apply to all their crosses, too.
It's unjust, of course, given all the dog-bite studies and genetic evidence at our disposal. Hence, why the new politics of breed ID would have us abandon our old ways in favor of a noncommittal approach to breed identification.
In other words, let there be no record of any veterinarian or vet staff's breed guess. Because not only is it probably wrong, as the science of genetic testing and other studies inform us, if it's legally on record that a dog is a member of a certain breed or a mix thereof, the possibility of an untoward outcome remains.
Which only makes sense. But will we alter our behavior to reflect the prevailing scientific winds or will we continue with business as usual? Given the average human's resistance to change, we're not likely to shift gears fast enough for some of our patients or their owners.
The good news is that once we stop regarding genetic tests as mere gee-whiz doodads for the pet addled and they finally gain the traction they deserve, our patients' lives will depend less on any ill-founded deductions we may advance and more on the increasingly irrefutable evidence the technology of dog breed ID offers.
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