Veterinary Voice: Health Testing 101 – Dr. Marty Greer
Dr. Marty Greer, DVM, JD returns to our Veterinary Voice series to talk about health testing for our breeding programs.
Using testing to improve our dogs’ overall health involves looking at both “phenotype” — diseases we can test for with xrays, blood or other physical exam — and “genotype” — those diseases identified by DNA testing.
Dr. Greer also provides some great input on the various DNA tests cropping up all around us. These tests, all spinning off from the identification of the canine genome, provide breeders, exhibitors and pet owners with a plethora of options for naming everything from the mixture of breeds in a shelter dog to the specific heritable genes for deadly diseases.
One of Greer’s primary points, which we’ll touch on again next week in our podcast with Dr. Jerold Bell, is that these health testing options provide breeders with the ability to *expand* their gene pools. Scientifically identifying a dog as a carrier and another as a non-carrier of a specific disease gene, for example, enables breeders to breed those two individuals with the assurance that none of the resulting progeny will be affected by the disease in question.
Many of our dogs are impacted by polygenic diseases, in other words something like hip dysplasia, for which there is no DNA test because it is predicated on more than one simple gene pair. Nonetheless, the future of breeding healthy dogs is made profoundly more “user friendly” with the available testing protocols for those who use them wisely.
“So, the tricky part, and I think the really hard part for people that as breeders are running these tests are for them to try and decide how to use that information in their breeding program,” Greer said. “… I see a lot of breeders who are so distraught about finding a genetic defect in their dog or in their line of dogs that they will throw out a whole line of dogs genetically. They will just stop breeding that whole line and it is narrowing and bottlenecking our gene pools even further than a lot of the breeds already are. So, we have to be really careful how we interpret and use those results.”
Greer goes on to discuss various health concerns and how those should apply to making breeding decisions.
“So, I tend to rank, personally, genetic diseases on a ranking of one, two and three, because you can’t treat them all the same,” Greer said. “So, things like an umbilical hernia, or an extra eyelash, you fix it once surgically, it is corrected. …the reality of it is those are not life-threatening diseases … Ranked two are things like allergies and thyroid disease, which require chronic medications. They always have to be on medication for those diseases if they have them. … And then ranked three are the things that are life-threatening, life-altering, life-changing diseases, and those are arthritic changes like hip dysplasia, seizures that are life-threatening, and, frankly, bad temperament in my opinion has the same categorization because some of those dogs have such bad temperaments that they bite people and that’s life-changing, life-altering and life-threatening. … I want to kind of frame it so people understand that not all not genetic diseases are the same, not all should be treated equally, and we have to really be thoughtful about how we use this information in breeding programs.”
The judicious and thoughtful use of health testing results and criteria in breeding healthy dogs presents almost a continuum of application in Greer’s experience. Potentially unhealthy dogs with no testing on one end and dogs with extensive testing but a potentially limited gene pool which may entrench diseases at the other end of the spectrum.
“…the Dandie Dinmonts, the Otterhounds, these people with small gene pools can serve as models for other breeds,” Greer said, “because even Labradors and Golden Retrievers are narrowed pools compared to what we have seen in the past. So, absolutely we need to be looking at these kinds of opportunities to perpetuate our genetics and not breed ourselves into such a bad corner that we end up with everything having a genetic disorder that is insurmountable, because some of these diseases are pretty serious and they become very ubiquitous in a breed.”
Listen to Dr. Marty Greer on Pure Dog Talk
Take a listen to the podcast or read the entire transcript for more insight from Dr. Marty Greer.
Veterinary Voice: Dr. Marty Greer
Laura Reeves: Welcome to Pure Dog Talk. I am your host Laura Reeves and we have, again today, our veterinary voice, Dr. Marty Greer. And she is going to talk to us about health testing and some of the things that are really important when we are doing our health testing, some of the things that are maybe a little bit confusing. So, welcome Marty. We appreciate your joining us.
Dr. Marty Greer: Thank you. I love being here.
Laura Reeves: Excellent. So, all of us working on trying to breed healthier dogs, and that involves doing some health testing. So, let’s talk about that a little bit.
Dr. Marty Greer: Well, it does get confusing and it does get complicated. And the most complicated thing is there’s all kinds of new DNA tests coming out for different breeds all the time. So, trying to keep up as a veterinarian can be incredibly difficult because the tests are coming out hard and fast. As breeders, it’s a little bit easier for you because you are specifically looking at one or maybe two breeds in your breeding program. So, you are aware of what your general breed club recommendations are, what they’ve been funding, what kind of health tests they are recommending, what’s listed on their website and what’s listed on the CHIC website. So, it’s a little bit easier as a breeder to keep up with all that than it is for a veterinarian. I have clients that come in every day and say I want this test and I’ll be looking at them like, okay, I have never heard of it, but I can look it up. Thank goodness for Google, right?
Laura Reeves: Oh, Dr. Google.
Dr. Marty Greer: So, by finding out what health tests are being done, it is easy enough to check with different DNA companies and assess what tests we should be doing, but there’s basically two general categories of health screening tests. One we call phenotype and one we call genotype. So, I want to make sure that we clarify that because I think just starting with that basic foundation makes it a lot easier for people to sort out what they are trying to be doing.
Laura Reeves: So, which is which? What are we talking about when we talk about a phenotype health test and a genotype health test?
Dr. Marty Greer: So, phenotype is something you can see. It is something you can see with an x-ray, with an echocardiogram, with your eyes, with your fingers, with a blood test, for certain types of things like thyroid. So OFA hips, elbows, patellas, shoulders, spine, trachea, all those different OFA tests, those are phenotype tests. The eye exam that is now no longer a CERF exam, but it is now also administered by the OFA, that’s a phenotype test. So, the veterinary ophthalmologist looks at your dog’s eyes and based on the appearance of a cataract, or a persistent pupillary membrane, or a retinal fold, or whatever it happens to be, they can determine if your dog has a phenotype abnormality in their eye. There’s hearts. So, if you’re listening, or you are doing an echocardiogram, you can assess it. Thyroid tests and a number of other tests for Addison disease and all kinds of other things that are chemistry tests will assess the phenotype of the dog. Genotype is based on the DNA. So that’s something that has to be done on a DNA level, it’s not something that we can see. You know, I might be able to see the phenotype. Like, I have Corgis, and one of the abnormalities that a Corgi can have is a fluffy coat. Now, they are absolutely adorable puppies and it’s not a health threat, so everybody loves fluffies and it is okay to have a fluffy, but there is a DNA test so I can determine if my dogs carry the genetic material for that. But I can also tell by looking at them. I don’t want to breed a fluffy to another fluffy because I’ll get only fluffy puppies. But I don’t know if I’m breeding a fluffy to a normal dog, what I am going to get unless I have that DNA test. So, there’s basically three kinds of DNA tests. There is the type that determines what breed your dog is, or what breeds, so that’s a blood test or a cheek swab that you can send into a diagnostic lab and they can say well your dog is 48% Bernese Mountain Dog and 52% Corgi.
Laura Reeves: Ouch!
Dr. Marty Greer: Or they can say, yeah, that’s a great look. There is a parentage test, so that’s when we can test to make sure that we know who the father of the litter is. Clearly, you know who the mother is, because that’s who the puppies are born from, but there can be times that you’ll want to know parentage either because of an accidental breeding where you had your bitch bred and then someone else came along and helped himself to her. Or you deliberately used multiple sires. So, in those cases you’ll want to know. Or if there is some question in the breed standard or in the stud book if you’ve incorrectly represented who the father of the litter is. Because that happens, perhaps more often than we would want to know about. And then there is the genetic disorder or genetic disease kind of test. So that’s the one that tests for retinal dysplasia, for a number of different kinds of DNA tests, EIC, CNM in Labradors. There’s multitudes and multitudes of these. And this is where every single week we’ve got new tests coming to the market from these amazing labs that are doing this testing, and it is absolutely incredible what we’re going to be able to tell in the next five to ten years, what we are going to be able to know about our dogs carrying genetically that we currently can’t tell by just looking at the dog or doing a phenotype test.
Laura Reeves: And I think that’s actually a really interesting topic, Marty, looking at where are going in the future in terms of, you know, we’re always going to have what you are talking about, the phenotype test, right? Look at a dog and say whether it has hip dysplasia or not. You are involved in this research, is there going to be a point in time that we can do a cheek swab and that DNA will tell us this dog carries the genes, multiple, for X, Y or Z disease?
Dr. Marty Greer: Yeah, and those tests are coming out hard and fast. There are some breeds that clearly have a disorder, so for instance, Addison’s disease we know we see it in Standard Poodles, we know we see it in Nova Scotia Duck Tolling Retrievers. So, when you see it in a small breed gene pool like that, they can look at the DNA, the entire DNA profile of that dog, and the labs that are doing this genotype testing can start to determine which gene is carrying that genetic material and once they know what gene it’s on in the Nova Scotia Duck Tolling Retriever, they may be able to apply that same testing to other breeds. They may, they may not. Sometimes it’s the same genetic flaw in every breed. Sometimes there are multiple genetic flaws. So, what is happening is a lot of these really progressive diagnostic labs now that the canine genome was understood by Elaine Ostrander and her group, these other labs can now take a look at the genome and start to figure out where some of these disorders are showing up representing the – on a gene or on an allele. So, it is pretty interesting because what these labs are doing is you may send your blood test in for DM and they may run on that same sample forty other tests, just because they are looking at these diagnostic labs to try and determine if that same genetic error in the Nova Scotia Duck Tolling Retriever shows up in the Pembroke Welsh Corgi, for instance. So, it’s kind of interesting to see and those tests are going to start coming to market faster, and faster, and faster because we are understanding the genome much better and these labs are doing amazing, absolutely amazing work in understanding where some of these tests are going to be valuable. So, the tricky part, and I think the really hard part for people that as breeders are running these tests are for them to try and decide how to use that information in their breeding program. So, if we have diseases that are autosomal recessive diseases, meaning that you have to have both parents being carriers are affected to produce that puppy, can use the carrier dogs in your programs for breeding and the answer to that is many times yes. But I see a lot of breeders who are so distraught about finding a genetic defect in their dog or in their line of dogs that they will throw out a whole line of dogs genetically. They will just stop breeding that whole line and it is narrowing and bottlenecking our gene pools even further than a lot of the breeds already are. So, we have to be really careful how we interpret and use those results.
Laura Reeves: Absolutely. So, specifically, we could pick one of the phenotype tests, right, and we could pick thyroid because I think that that is one that is A, difficult for some folks to understand and B, crosses a lot of breeds in terms of being an issue. And we have spoken to Dr. Dodds and we have had some conversation on this, but I would like to take it to a really basic level of, okay, this is the blood test you have to do, this is the results you might get, and this is what those results mean.
Dr. Marty Greer: Right. So, what you have to start off, the basic premise, and what I tell all of my clients are that there is no perfect dog. There is no genetically perfect dog out there. There is no genetically perfect human. And humans are the most out-crossed species on the planet. We travel across the world and we don’t have linebreeding most of the time in people. Every now and then it happens, but usually not. So, even despite that genetic diversity, every human that I know has at least one genetic defect. My mom had hip dysplasia, my dad had allergies. They should not have bred. I should not be here. They didn’t health test my parents before they bred. So, I was lucky I didn’t end up with either one of those things, but my sisters have allergies. So, the question then becomes what do you do when you have a dog that has something that’s not perfect about it? Because I can tell you every dog has something imperfect about it. So, I tend to rank, personally, genetic diseases on a ranking of one, two and three, because you can’t treat them all the same. So, things like an umbilical hernia, or an extra eyelash, you fix it once surgically, it is corrected. AKC doesn’t like that, but the reality of it is those are not life-threatening diseases and those are things that with one surgical procedure you can fix, and to me that’s not an overwhelmingly terrible thing to have. Ranked two are things like allergies and thyroid disease, which require chronic medications. They always have to be on medication for those diseases if they have them. So, my question to you would be, well, how hard was it to live with your allergic dog or your hypothyroid dog, and would you want to take another one of those? Would you expect someone to buy a dog from you if it has the potential to need thyroid medication from the time it is four years old for the rest of its life? And then ranked three are the things that are life-threatening, life-altering, life-changing diseases, and those are arthritic changes like hip dysplasia, seizures that are life-threatening, and, frankly, bad temperament in my opinion has the same categorization because some of those dogs have such bad temperaments that they bite people and that’s life-changing, life-altering and life-threatening. So, I think temperament, even though there is not a phenotype or a genotype test for that and perhaps never will be, we have to think about all those things. So, I don’t want to stray too far from the thyroid thing, but I want to kind of frame it so people understand that not all not genetic diseases are the same, not all should be treated equally, and we have to really be thoughtful about how we use this information in breeding programs.
Laura Reeves: So, with the thyroid test, we will just pick on thyroid again because it’s so prevalent, you do your blood test, you ship it off to a particular laboratory, right? OFA uses MSU, and something else, I can’t remember, and you get your results back and one that I find frequently, just as a personal experience, unfortunately, I see a lot of equivocal.
Dr. Marty Greer: Right.
Laura Reeves: So, can we talk a little bit, because I think there is still confusion amongst folks about what that actually means in application to the dog and in application to a breeding program?
Dr. Marty Greer: Yeah. And equivocal means you should probably wait six to twelve months and retest and see what you end up with for a result, because it may mean that your dog was having something going on in its life that affected its thyroid level. According to Jean Dodds, heat cycles can affect it, if the dog is ill from some other reason, you know, if the dog has Lyme disease it can look hypothyroid. There’s a lot of other disorders that can interfere with the thyroid levels. So, on one test if it comes back equivocal, I would not throw that dog out of my breeding program. I would retest in six to twelve months and see where you stand and if at that point it is clear that the dog is hypothyroid or has the risk to become hypothyroid, meaning the autoantibody levels are starting to rise, then I would consider seriously whether that dog should be in my breeding program. Or if it is in the breeding program, make sure that you’re not breeding to another dog that had any history of equivocal or hypothyroidism. On the other hand, if the dog is normal until they are three or four years old, and many times you do need to test more than once for thyroid disease, as you do for eyes and some other disorders – hearts. If you have a Doberman you’ve got to test frequently – then those are the dogs that if they are normal at three to four, probably are going to remain normal through the rest of their life or at least not have an inherited disorder caused by thyroid disease or autoimmune disease causing hypothyroidism. The problem is that it costs a lot of money to do these multiple tests, it is sometimes hard to interpret them, and it is a challenge to try and figure out exactly what you should do with your breeding program. The other difficulty, and I don’t think this has been well-discussed yet, is there are probably differences in breeds. That a Samoyed isn’t necessarily going to have the same thyroid level as an English Setter. So, until some of the diagnostic labs really break this down for us, or our breed clubs finance some of the research that it is going to take to determine this, it is a little hard to know if your results are actually as accurate as you would like to believe that they are. And it’s not that anybody is trying to pull the wool over your eyes, it is just the reality is there are probably going to be differences in different breeds.
Laura Reeves: That’s actually a really fascinating topic. I don’t know if we can go any further with it, but I have actually heard that theorized and is there any kind of data, any kind of research at all, or is this just sort of people think that? I don’t know, where are we on that?
Dr. Marty Greer: I’m not sure that I can speak completely to it because it’s outside my area of expertise, but I know at one point the Samoyeds were working with Minnesota, their veterinary school, to try and determine if there were some breed variations. So, I think that’s really valuable information to have before you’re going into a breeding program. So, if you have a breed club that has some money and they’re looking at research, thyroid disease may be one of the places to look. Of course, cancer, you know there is a lot of inherited cancer. There’s a lot of places breed clubs are asked to spend their money to try and determine what kind of tests are best used for those breeds, but thyroid disease I think is going to be a very interesting one to see. Dobermans, Golden Retrievers, they walk in your door, if they look hypothyroid they probably are. It is really common in those breeds. Other breeds we just never see thyroid disease in. And then there’s – Jean Dodds had some discussions about thyroid disease and its relationship with temperament, so it gets complicated. It really gets very difficult. So, I don’t want to make this any more confusing, but we do have to look at this and say you can’t just look at one genetic test for your dog and unless it is one that causes a life-threatening, life-altering, life-shortening disease, you don’t want to throw the baby out with the bath water. You have to really look at what the whole dog’s genetic makeup is, how the dog fits together in a breeding program with other dogs, and just be really careful with your gene pool that you’re not bottlenecking it or narrowing it any further. The Dandie Dinmont Terrier Club has worked really hard with one of the DNA testing labs to try and develop genetic diversity within their breed, because that’s a very, very small gene pool as a number of others. So, they have been able to look at DNA tests on those dogs and genetically diversify that breed by doing further outcrosses than what some people would have normally done and they are still producing dogs that are quality enough dogs to win in a Dandie Dinmont ring, but they’re developing a more diverse gene pool. The only other way that breeds are going to be able to develop diversity in their gene pool is to breed outside their breed, and so much for AKC and pure-bred dogs if we start doing that, so we have to start looking at some of these places that people have done research and been effective, like the Dandie Dinmonts. The Otterhound people are starting to figure out a way that we can increase the genetic diversity by freezing semen on dogs that aren’t necessarily show dogs but are in pet homes. They are working with the AKC to develop a gene bank.
Laura Reeves: They have a semen bank! I am so excited. I just did an interview with the gal who created that and put that together. I am super excited to talk about that.
Dr. Marty Greer: Right. Those, the Dandie Dinmonts, the Otterhounds, these people with small gene pools can serve as models for other breeds because even Labradors and Golden Retrievers are narrowed pools compared to what we have seen in the past. So, absolutely we need to be looking at these kinds of opportunities to perpetuate our genetics and not breed ourselves into such a bad corner that we end up with everything having a genetic disorder that is insurmountable, because some of these diseases are pretty serious and they become very ubiquitous in a breed.
Laura Reeves: Okay, well I know that you have a busy day ahead of you and I appreciate your time tremendously, Marty, and I look forward to talking to you more in the future.
Dr. Marty Greer: Great. Thank you.
Laura Reeves: Thanks a lot.
[Length: 16 minutes, 33 seconds]