DNA testing results
Jenna Dockweiler, MS DVM, DACT, CCRT, CVAT, and Lindsey Kock, DVM, share ways to be proactive about conditions that may occur in dogs from DNA testing results.
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Adam Christman, DVM, MBA: I want to expand on how we effectively communicate that to the pet owner because sometimes all they might think of is hip dysplasia like you just mentioned. But it's prognostic, not diagnostic, so share with us some examples that you can say in the exam room with clients when talking over the genetic results.
Jenna Dockweiler, MS DVM, DACT, CCRT, CVAT: So if we have the penetrance information— which is how likely it is for a dog that is at risk for the condition—to go on to develop the condition, that will be listed in the report. For example, there's a certain type of progressive retinal atrophy, the progressive rod cone degeneration (PRCD) type that has a 98% penetrance. That means that 98% of dogs that are at risk for that condition will go on to develop some degree of vision loss, which is a very high penetrance example. For something like that, we can go in and say "Hey, it's likely that your dog is going to develop vision loss over the next several years. Here's what that looks like. They're going to lose night vision before they lose day vision. You might notice that they don't want to go outside when it's dark. You might have to turn a porch light on for them, that sort of thing.”
With conditions where the penetrance either isn't known or is not quite as high as that condition, we can say, "Hey, there's no guarantee that your pet will develop this disease, but here's all of the steps that you can take to ensure that if this disease does develop, that we catch it early and we have the best chance to respond to treatment."
Adam Christman, DVM, MBA: I love that. I think having that proactive approach to care versus a reactive approach is so nice. And for pet owners to absolutely be walked through what to expect—it may not happen—but just to know, like, “oh yeah, I remember she talked about that in the exam room four years ago” so this is where we're going down that path. And when you have these results too, does it alter the treatment plan or diagnostic approach? What does that look like?
Lindsey Kock, DVM: We've talked about urinary disorders. I think the other one for me is risk for heart disease. There’s, in a general practice, a lot of times, pretty minimal diagnostics that we do in terms of looking at the heart's function beyond physical exam and auscultation, right? So in the past, our first sign of heart disease would be either clinical symptoms or the presence of a murmur most of the time. And if we know that a pet may be at increased risk for heart disease, we may be able to be a little bit more proactive about diagnostics for heart monitoring and potentially treating early too. So, being preventative with a heart-healthy diet, as an example.
I know the way that we use some of those heart medications is changing too, and rather than initiating that when we have symptoms, we may be able to get that started when we know there is a risk a lot earlier on progression of the disease. So for anyone who's managed a congestive heart failure case, quality of life for those guys is huge. So I think if you can extend that for a pet, that's awesome.
Adam Christman, DVM, MBA: Okay, so we just talked about surgery. I'm sure you all heard of “white feet, don't treat”. So what does that mean now that we have genetic testing in play?
Lindsey Kock, DVM: I started my career in large animal medicine, right? So the “white feet, don't treat,” was really thinking about ivermectin and inadvertent use of, you know, large animals dosages on dogs, and that was the thing that we worried about. What I've learned in learning more about genetics is that MDR1 affects the metabolism of so many different medications that we commonly use. So within normal dosages and limits for ivermectin, and those similar classes of drugs is really pretty safe, but other things that we need to think about are chemotherapy agents and also anesthetic agents, stuff that we use all the time where those dosages should be adjusted for those dogs.
Adam Christman, DVM, MBA: Do you hear that a lot in your neck of the woods?
Jenna Dockweiler, MS DVM, DACT, CCRT, CVAT: Absolutely, and we see it in far more than just herding breeds these days now that we know what the mutation is and we can test for it. It's not just “white feet, don't treat” anymore.
Adam Christman, DVM, MBA: Right, yeah. So tell me more about that conversation because this is very popular in vet med. In fact, I think a lot of pet owners hear this more than veterinarians sometimes. What do we do with that moving forward when they say, "Well, what do I do for, you know, parasiticide therapy? Like, what does that look like?"
Jenna Dockweiler, MS DVM, DACT, CCRT, CVAT: All of our preventives that are FDA approved for use in the U.S. are safe for dogs with that MDR1 mutation. So, from that perspective, it's not necessary a concern. However, if you want to use acepromazine or butorphanol as pre-medications or for pain medications, then it potentially could be a concern. This is really more of a personalized medicine type of test because these dogs are otherwise perfectly healthy, there's nothing wrong with them, they just metabolize their drugs a little bit differently.
