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Susanne Björnefeldt avhandling

Hundens genetik modell för medicinsk forskning
Nya forskarrön vid Uppsala Universitet – läs pressmeddelandet här

Projekt atopisk dermatit hos hund – dagsläge och fortsättning
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Analys av avelsstruktur – inavelsgrad och effektiv populationsstorlek av Sofia Malm och Birgitta Danell

Parning och valpning av Maria Nordin

Avel i små populationer.
Genförluster
SKK: Möjligheter och begränsningar med DNA-tester
Fyrbenta vänner med stor variation.
Avelsstrategi för små hundpopulationer
Avhandling om Nefrit hos Bullterrier.
Jordbruksverkets nya regler om hundhållning.
Genetisk studie av inavel och fertilitet hos hund.
PM Angående beräkningar av inavel i SKK Avesldata och Lathunden.
Gen indikerar tvångssyndrom hos hundar.
Studier på hund avslöjade starka riskfaktorer för SLE.
Föreskrifter och allmänna råd om träning och tävling med djur

Publiceras med tillåtelse av David Harris
Some Thoughts on Health Testing
David Harris
December 2006

Ten or so years ago, with rapid advances being made in canine genetics, I was excited about the prospects of DNA-based health tests. With such tests we as breeders would be able to significantly reduce or even eliminate inherited diseases in our Bull Terriers. Unfortunately my excitement was premature. Today, in late 2006, we have no genetic tests for our Bullies. And even when such tests are developed they won’t necessarily be 98-100% accurate. The first canine test to be announced, with much fanfare, was one for detecting carriers of copper toxicosis in Bedlington Terriers. This test does not look for the bad gene(s) directly; rather it looks for a “marker” – a unique sequence of DNA that can be readily identified. If that sequence is close to the bad gene then it highly likely that a dog testing positive for the marker will carry the bad gene and vice versa. However, the further away the marker lies from the bad gene, the less probable it is that the bad gene was inherited along with the marker sequence and hence the less accurate the test. Well my acquaintances among Bedlington breeders no longer use the test because it gives too many false readings, its accuracy being somewhere in the 70-80% range (this is their guess). Imagine if your prize Bedlington tested positive as a carrier for copper toxicosis, but in fact didn’t carry the gene. Breeders simply can’t rely on this test.

The bottom line is that it could be many years before a definitive and accurate set of DNA-base tests become available for our Bullies. In the meantime we have to depend on the tools we do have – common sense and veterinary tests that indicate whether or not our Bully is suffering from the disorder or disease at the time of the test. The Bull Terrier Club of America recommends testing all potential breeding stock for four inherited disorders – deafness, heart defects, kidney problems and slipping patellas – using protocols defined by the OFA (Orthopedic Foundation for Animals). Also to register a dog as clear of the last three disorders he or she must be tested after the age of 2 years. This is not a magic age, but in the majority of cases such problems will show themselves by then. The testing should continue throughout the breeding life of the dog, especially in the case of heart defects, which are arguably the most widespread problem in Bullies today.

But even though a dog tests clear of a disorder, it may still be a carrier. And bred to another carrier the resultant pups may develop this disorder as well as being carriers for it. This is our biggest challenge. Let me discuss a well-known example from the 1960s. Ormandy Souperlative Bar Sinister, one of the most famous Bullies of all time, was a monorchid, in other words only one of his testicles descended into the scrotum, though later in life this second one did come down. Raymond Oppenheimer, when later justifying his making Bar Sinister available at stud in, explained that he produced proportionately fewer monorchid puppies than did either of his litter brothers – Sea Captain and Masta Plasta. In other words Raymond argued that you were taking no greater risk by using Bar Sinister as a stud than you did by using either of his brothers. We will return to Bar Sinister later. Over the years there have been many stud dogs, which – though not showing one or other of the inherited disorders themselves – were clearly carriers and produced quite a few offspring with the disorder. I am discussing males here, but of course the same applies to bitches, which must also carry the bad gene(s) if any of their pups develop the problem.

Until effective DNA-based tests are developed there is no way of predicting which Bullies carry which disorders, though clearly there is a much higher probability of their being the carrier of a particular disorder if it has appeared close up in their family lines. Our only defense here is to be open and honest about problems. Much depends on the owners of popular stud dogs, who should not only test their studs regularly, but also inform breeders of any defective puppies he has sired. In the case of carriers, remember the bitch is just as much to blame as the dog. It takes two to tango as the saying goes. It frustrates me greatly to hear a breeder bad-mouthing a stud dog for producing a puppy with an inherited disorder, while completely ignoring the fact that their own bitch was just as much responsible for the problem

We all need the best information available about inherited diseases and testing for them. As breeders we need to educate ourselves on these matters, while Bully clubs should facilitate this education and make testing readily available

Next we should address the question of how best to avoid or at least reduce the occurrence of these diseases in our Bullies. One approach, and perhaps the most obvious one, is to eliminate from our breeding programs any Bully that fails any of the health tests. But what happens when we come to a Bar Sinister? There we had a dog clearly superior in type to his contemporaries. And if we eliminate Bar Sinister then shouldn’t we also eliminate his two brothers, who were clearly carriers of the problem from which Bar Sinister suffered? I doubt that we could find today anywhere in the world a Bully of quality and type that doesn’t go back to Bar Sinister many times and probably also to Sea Captain. Yes, using the three brothers at stud did increase the occurrence of monorchidism in the late 1960s and into the 1970s. But the frequency declined thereafter and fell back to being an occasional problem in Bullies.

What would you have done if you had lived in England in Bar Sinister’s day? Would you have sent your bitch to him? To one of his brothers? I suspect I would have taken the same path as did D Montague Johnstone and Meg Williams at Romany; I would have used his brothers, but not Bar Sinister himself. And I might have been right, but not for the right reason. Bar Sinister was withdrawn from stud after only three and a half years because he had, in the words of his owner, “a bad heart”. Most likely he suffered from an inherited heart condition. But that was at a time when we thought little about heart problems and their heritability.

If we removed from the breeding pool all Bullies that either suffered from a heritable condition or had produced a puppy that suffer from one, we wouldn’t have many Bullies left to use. Be aware that all Bullies, all canines and equally all humans carry a number of “bad” genes. Genetic counsellors inform us that we need a gene pool big enough to maintain a healthy breed. With too few Bullies, we would simply concentrate the bad genes that those few remaining animals carried, thereby creating a new set of problems. Consider the challenges faced by breeders of Miniature Bull Terriers. Blindness due to lens luxation, an inherited disease, is widespread among Minis. And to make matters worse the disease sometimes does not manifest itself till middle age. If all Minis, that either suffered from lens luxation later in life or produced a puppy that eventually went blind, were removed from the gene pool, there probably wouldn’t be many Minis, if any, left to breed from. Oh how desperately Mini breeders need a DNA-based test for lens luxation! (And, of course, research is being carried out to identify the gene(s) that cause lens luxation)

What I have been arguing in the last few paragraphs is that simply eliminating lots and lots of dogs from those available for breeding is not a solution to our problems. We need to be more judicious (thoughtful). We need to use common sense in our breeding programs. In America we have some Bullies that have serious compulsive behaviours – tail chasing and the like. Genetic research into these behaviours is currently being funded. What frustrates me here is that we only have this problem because a few breeders used dogs with mild signs of tail chasing and eventually the problem reached serious levels. Common sense should have dictated that such dogs be eliminated from breeding programs. Equally we have no reason at all to use dogs that are deaf or unilaterally deaf. The latter are deaf in one ear and – to the best of our current knowledge – unilaterals have the same underlying genetic defect as bilaterally deaf dogs.

Ideally we should not breed from any dogs knowing it has an inherited problem. But at any one time we tend to have one or more health disorders that are so widespread in Bullies that we have to take a pragmatic approach to reducing the incidence. Kidney disease was such a problem in the late 1970s and early 1980s after the extensive use Souperlative Jackadandy of Ormandy. We eliminated many of Jackadandy’s get from the breeding pool – and of course many died prematurely – but we used his remaining get judiciously, progressively reducing the incidence of kidney disorders such that it is no longer common, certainly among the Bully lines with which I am familiar.

Today heart diseases, in particular mitral valve dysplasia and sub-aortic stenosis, are a major concern. Ten or fifteen years ago few of us had to worry about heart defects; now it is difficult to find a family line that is demonstrably free from them. Awareness came too slowly; too few breeders tested their dogs for heart murmurs; while others irresponsibly knew about but chose to ignore problems with their dogs. The result – heart problems are now widespread. Many sires that test clear of heart problems into old age still produce quite a few pups that are afflicted. Heart murmurs are graded, according to the OFA test protocol, from “1” to “6”, where one is a very soft murmur and six is loud even when the stethoscope is lifted from the dog. So this isn’t black and white like deafness, heart defects are a matter of degree. A grade one murmur may never get worse and have no impact on the dog’s activity or its lifespan. On the other hand higher grades indicate serious heart defects with resultant infirmity and shortened lifespan.

Here again we have far too many Bullies with low grade heart murmurs, or that have proven to be carriers, or have close relatives with problems, to throw them all out of our breeding programs. How many family lines with no incidence or history of heart defects are you aware of? So again we must approach reducing the incidence of heart problems by using the best information available to us and by making judicious selections in our breeding programs.

If you find some of these thoughts depressing, take heart. Working honestly and openly together we can move forward and continue to improve the health of our dogs. Back in 1979 I mated a bitch to Jackadandy, not knowing about the serious kidney problems he passed on to so many of his get. After losing a young bitch to kidney failure, I went to work to research and understand the problem I was facing. With the help of urine tests (protein/creatinine ratios) I was able to overcome the problem and have not had another kidney problem in the Bullies I have bred since then. During 35 years of breeding Bullies I have always focused on the character and temperament of my dogs, going out of my way to exhaustively check these characteristics (1) in any family lines I have chosen to introduce into my breeding program. And I believe, in all honesty, that I have been highly successful in this regard – witness the intelligence and personality of my Bullies. Working together we can achieve whatever we set out to do.

Please be aware that these notes are my own personal views, not those of any club or organization to which I belong. No doubt some readers will disagree with some of what I have written. But hopefully these notes will provide food for thought and generate discussion about the health of out Bullies.

I wish Bull Terrier fanciers in Sweden every success in breeding happy, healthy dogs.

Footnote (1): These characteristics, good and bad, result from both inherited and environmental factors – often referred to as nature and nurture. Obviously we ourselves control the way our dogs are raised and socialized. But it equally important to select dogs of the best possible character and temperament as these are highly heritable traits.