GENETICS
by Patricia Princehouse
Translated from an Open Letter to the membership of the Reunion des Amateurs des Chiens Pyreneens (Translation into English by the Author) originally published in the RACP Bulletin, Spring, 1998 Alain Pecoult, editor
| Dear friends, My many years as a member of the RACP have brought me much joy. I have on many occasions been extremely impressed with the knowledge, skill and dedication of owners and breeders of Great Pyrenees and Pyrenean Shepherds (and at a little more distance, of Gos and Mastins). I am extremely grateful to many breeders for trusting me with valuable breeding stock, and knowledge of the particular virtues and faults of the dogs making up their pedigrees. Even beyond this, I thank the RACP for allowing me to experience a unique attitude, an atmosphere quite different from that in North America, a special reverence for breed type above all else. I hope that this article may be useful to readers, and that in this way I may be able to give back a little to the RACP, which has given me so much of great value. I admire profoundly the skill that has allowed breeders of our four breeds to maintain excellence in type, movement and overall health throughout the centuries. As the world enters an era of increasing scientific sophistication, I applaud the growing interest of French breeders to determine the extent to which theories of genetics and medical diagnostic technologies could perhaps aid them in maintaining the health of their bloodlines. Such methods were of course not available traditionally. Throughout most of the past thousand years or so, the ancestors of our dogs underwent tests of a different kind. Death, often painful, came to dogs whose constitutions did not allow them to withstand many kilometers of running, long periods of exposure to the elements, periods of starvation, etc. The high incidence of consanguinity within each mountain valley served to reveal the defects within the breeds and eliminate the most severe problems. I believe this is why all four of the Pyrenean sheep industry breeds, especially the Pyr Shep and the Gos, are among the healthiest purebred dogs in the world today. Deleterious genes exist in every species of biological organism, from lemurs to cockroaches. And such defects are found in every race of human (no matter how you choose to define race), and in every bloodline of every breed of purebred dog, and in mixed-breed dogs as well. Even the demanding conditions of life in the Pyrenees mountains were not able to eliminate all these problems from the gene pool. Some traits considered unpleasant by show breeders and pet owners do not cause problems to the working dog except in their most extreme manifestations. For example, epileptiform crises are scary to pet owners and we try to avoid breeding such dogs, but a mildly affected dog (such as several of the Pyr Sheps I've seen in North America and France, and those reported from Finland), one who has a shaking fit lasting maybe a minute or two, perhaps 3 or 4 times a year, would not have been impeded in any way from fulfillment of his duties. Even when a defect is quite serious, the number of dogs in a population which manifest a (recessive) trait is still only a small fraction of the number of dogs in the population that carry that trait in their genes but show no sign of it. Imagine a population of 100 Mastins in the middle ages, guarding the sheep of a number of villages in a remote mountain valley in Northern Spain. This population is relatively isolated from outside migration and all the dogs have good eyesight and perform their work well enough. Now imagine a puppy is born with a spontaneous mutation which causes him no trouble at all, since he only carries 1 copy of it, but would result in progressive retinal atrophy if he carried it on both his chromosomes (remember that each dog has a pair of each of the 39 chromosomes, humans have 23 pairs of chromosomes, a mammal carries 2 copies of each gene, one on each chromosome). It doesn't matter whether the new gene comes from a mutation or the migration of a new animal into the population. If you prefer, you can imagine that a young shepherd moves into that remote valley seeking refuge from the Inquisition, bringing with him a lovely big male Mastin (which the neighbors instantly suspect was probably stolen from a nobleman). The dog is huge, with perfect dark head markings and saddle. Just the scent of such a dog causes wolves, lynxes and even bears to pass on to the next valley in search of easier prey. This dog is unaffected by the gene he carries (a gene which, if possessed in two copies would result in retinal atrophy blindness, but is harmless possessed in only a single copy). Not everyone likes this stranger, but they like his big dog. Even people from villages on the other side of the valley, who would never dream of speaking with the young man, will, nevertheless, take their bitch in heat and tie her to a tree near his cabin in the hope of getting pups sired by the big dog. After several years, someone reports the man to the Inquisition and soldiers come and take the man away to prison. He never comes back, but another villager claims the stranger told him he could keep the dog. Over the years, this dog breeds many local bitches. Since the local bitches do not have this gene, and the male only carries it on one of his two chromosomes, only half his pups end up carrying this gene, and none of them are affected by the blindness. After a few more years, the dog dies and is remembered only in stories, if at all. There are now many fine big dogs in the valley. The overall population of Mastins is still around 100. The hard-working villagers cannot afford to keep any more dogs than are strictly required to keep predators away from the sheep. At this point, 15 of the 100 Mastins in the valley carry the PRA gene. They are spread across the valley and chances are very low that any 2 of them mate. Even if 2 of them were to mate, only 1 in 4 of the puppies would have 2 copies of the gene and eventually become blind. After several more generations, 32 of the dogs in the valley have a single copy of the gene. At this point, statistically, it becomes likely that 2 carriers will mate. Perhaps a bitch owned by a person living many kilometers from where the stranger stayed, a person who never even heard of this stranger and his dog, has a litter of 10 puppies. Two of the puppies have the PRA gene on both their chromosomes. Four of the pups die shortly after birth. This is normal. One of them had 2 PRA genes. Six puppies survive. Four of them are traded to other villagers for goods and services. At 9 months of age, the two pups kept by the shepherd are playing rambunctiously near the edge of a cliff. One of the pups races toward the other two, they leap out of the way, and he runs straight off the cliff and falls to his death. That was the second pup with two copies of the gene. It was the first individual affected by the disease, even though the gene has been floating around in the population for 50 years and nearly a third of the dogs in that valley are carriers. The shepherd curses his bad luck at losing such a fine young dog to such an stupid accident, and makes a special trip to church to light a candle in the hope his luck will be better in the future. Remember that even though one third of the population carry this gene, the majority of dogs do not carry it at all, even dogs inbred on dogs sired by the stranger's dog (half the stranger's dog's offspring are completely free of the gene). The stranger's dog had a very beneficial influence on dogs in that valley. Fewer sheep are lost to wolves and bear, and the economy flourishes such that a few people are even able to sell a few sheep for cash money, a rare event in a subsistence economy. The people may never realize that some of their dogs are blind. Whenever the proportion reaches about a third, pups with 2 copies of the gene will start being born, and they will fall off the mountain (or something else will befall them) and they will die before they reach maturity or produce puppies. This natural selection will slow the spread of the gene within the population. Inbreeding increases the opportunities for 2 copies of the gene to end up in the same puppy, and so, helps check the spread of the deleterious gene through the population. But here in the twentieth century, we don't have this level of natural selection operating. Most puppies do grow up and some are affected by genetic defects, much to the heartbreak of their owners. What should we do about this? The joy of breeding dogs does not lie in constant fear of defects. The joy lies in producing positive traits, dogs of outstanding type, gait and temperament who are a joy to look at and live with. By way of answering this question, I can tell you my own story of coming to terms with these issues. As a young child, I loved to visit the house of a neighbor who bred and showed Siberian Huskies. I loved the puppies and was entranced by trophies and the photos of show wins. But I didn't want a Siberian, I wanted a dog as big as a horse. I read every book I could get my hands on. They said many conflicting things about the different breeds. Through the local kennel club, I found out that purebred puppies are very expensive, often $300/1500FF (in the early 1970s). However, I found a puppy for only $50/250FF. This puppy was not inbred. In fact, it was half Great Pyrenees and half Newfoundland! It grew up to have hip dysplasia, serious skin allergies and some temperament problems. And I learned that even though it was black and looked like a Newfoundland to me, I could not show the dog. So, in 1977, my family bought a purebred Pyr, with papers, in the hopes that I could have something to show. We spoke on the phone to several breeders, visited adult dogs bred by the breeder that interested us, drove very far, 6 or 7 hours, to pick up the pup. And we were assured by her that hip dysplasia was very rare, and that the father of the puppy was a champion and had been x-rayed. Yet, at the young age of 4 months, my show dog began limping and crying. He had hip dysplasia just like the unpedigreed dog had. At this point, I had spent half my entire life trying to get a show dog, and still did not have one. Just when we were about to give up, a friend told us about 2 Pyrs a man was trying to sell. The man was getting a divorce and wanted to get rid of the dogs at a very reasonable price. So, for $100, we obtained a male and his year old son. We were extremely lucky. We didn't understand it at the time, but a little research showed that this male had an outstanding pedigree. --And he had good hips! The son was of overall lesser quality, and his hips were not as good, but he was good enough to do some nice winning for me at shows. We got a good bitch, also with good hips, and bred several litters. I found that even when both parents had good hips, about 5-10 percent of the pups would still have hip dysplasia. This was my introduction to the world of purebred dogs. When I was 15 years old, with the encouragement of my grandmother overcoming the doubts of my parents, I spent the summer in France. I was able to attend the Paris championnat (at that time still held at the Porte de Versailles), and the specialty at Deauville. I visited many people and they were all very gracious. I loved the dogs I saw. They had such power in their gaits and such beautiful expressions. And I fell in love with the Petits Bergers des Pyrenees. Over the next decade, I and other North Americans imported numerous dogs of both breeds from France. We found, to our disappointment, that the rate of hip dysplasia was not any lower in the French dogs, in fact, it was higher. Some 50% of Pyrs imported from France and 20% of Pyr Sheps have proven dysplastic. This doesn't sound very good, but look at it the other way around: even though none of the French breeders were x-raying their dogs, 50% of Pyrs and fully 80% of Pyr Sheps were free of hip dysplasia. Many of these were certified by the American central authority, the OFA (Orthopedic Foundation for Animals). And some of the Pyrs (though so far none of the Pyr Sheprs) imported from France have received the very highest hip rating. I have found that French-bred Pyrs with good hips produce no more dysplasia than my American dogs with the same rating. In cases where a dog possessed some rare virtue such as an outstanding head, I have experimented a bit with breeding dogs whose x-rays are not good enough to certify, and I find that it is difficult but not by any means impossible to produce pups with good hips when one parent is mildly affected by dysplasia. Over the years, I have found that by using only dogs with the 2 highest hip ratings, the hip joint conformation has improved so much that it is now not unusual for half a litter to receive the very top rating. It is more and more rare that one of my pups turns out to have dysplasia, less than 3% in the past 10 years. In the Pyr Sheps, where our stock came entirely from France, we have reduced the incidence of hip dysplasia to about 5% in just 1 to 2 generations of breeding only dogs who received the 2 highest ratings. Both Mr. Mansencal, and Mr. Pecoult have judged our national specialty several times. Both assure us that our dogs have excellent type, movement and temperament. So, in my opinion, it is possible to decrease the incidence of genetic defects while still preserving type. Preserving type is, after all, the only reason one should be breeding. Why does it matter? Why x-ray? Why do I encourage you to use the new diagnostics? Well, one reason is because they are available at low cost and can do so much good. In the 1970s, when I bought pups with hip dysplasia (from both France and the USA), the pups were severely and painfully affected. All were euthanized well before age 8 because they were going through so much pain. Today, although a certain minimum number (3%) of my puppies may still show radiographic evidence of mild hip dysplasia, they have little pain and their owners would never know their hips were less than perfect until they get to be over 10 years old and arthritis sets in. That makes it worthwhile. Also, although a dog with hip dysplasia can in some cases have an excellent gait, and even though a dog with perfect hips may still have a horrible gait for other reasons, even so, I believe that the gaits of my best dogs are better than they have ever been. I visited a breeder in Europe a number of years ago. He was forced (by the club) to x-ray his dogs, but he said he just goes ahead and does what breedings he was going to do anyway, regardless of the hip x-ray results. This seems like a sensible enough attitude given his situation. And yet, I notice that when I ask him how certain dogs did on their x-ray, virtually none of his younger dogs did poorly. I think that just having the information helped him improve his dogs, even though he claims not to have made a conscious effort. What about other problems? The only other problems we've encountered from French imports are: 1 case of patella luxation in a Great Pyrenees (she was otherwise quite lovely but also had mild dysplasia. Her breeder sent me another pup for free with the understanding that if I ever bred the first one, I would then pay for the second one. I never did breed her, though I was tempted to. She lived to be more than 14 years old.), and about 20% of the Bergers imported to the US have had some degree of epilepsy. I have been very pleased with the Pyr Shep breeders' willingness to discuss epilepsy when I have approached them in a calm, rational way. This has helped me greatly in reducing the incidence. Less than 10% of the Pyr Sheps born in North America have had epilepsy, and the cases are becoming rarer and less severe (often they have 3 or 4 petit mal seizures a year and even these don't start until age 3 or 4. Only 2 dogs have needed medication). My advice on both patella luxation and epilepsy is: don't breed an affected individual unless the dog is absolutely gorgeous in every other respect and has qualities you cannot find in another dog. I have used 1 epileptic for breeding and I feel it was justified because of her outstanding type. I have never used a dog with patella luxation. In fact, I palpate the knees of all my puppies at 5 and 7 weeks and every 2 weeks thereafter as long as I have them. Most of my pups have good knees. But occasionally pups show more luxation than usual. These pups I place as pets. Usually as they get older, the looseness tones up, but I think they are still poor bets for breeding from. I have had 2 Pyr pups (in addition to the import mentioned above) whose knees were so loose that their patellas would pop out to the side and they would momentarily be unable to bend their legs. This hurts and the pups would often yelp and fall down. I euthanized these pups. I do not believe in surgery for knees or hips (other than simple cutting of the pectineus muscle) in big dogs, and don?t recommend it for the little dogs. These dogs usually mess up their surgery by putting too much weight on the legs too early or by running too much too soon. I have seen many dogs from other bloodlines (patella luxation has long been a problem in North American-bred Great Pyrenees) who have had these operations. In my opinion the dog was better off before the expensive operation. In many cases they had to be euthanized in spite of the operation (after weeks of suffering because of the operation). I have my dogs' eyes examined every few years by a veterinary opthamologist. It is not expensive and I have the peace of mind of knowing that none of my dogs has ever had PRA or symptoms of any other hereditary blindness. Soon, there may be an inexpensive genetic test for carriers of PRA. Such tests should be used wisely. Just because a dog is a carrier of PRA, should not automatically keep it from being bred. But it should not be bred to another carrier. What about heart troubles? In 20 years of breeding Great Pyrenees, I've had 1 stenotic aorta and 1 stenotic pulmonary artery. These came from litters born 10 years apart and whose pedigrees didn't share any dogs in common for some 10 generations. Both were detected easily with a stethoscope before 2 months of age. So far, in a population of 120, we have had no PDA in Bergers (although some lines of North American Pyrs have some incidence of PDA). I understand there have been 2 Pyr Sheps with PDA in Finland (in a population of 360). It is important not to become hysterical. Although I have no specific experience with this problem, it seems to me that the thing to do is to survey the population and try to figure out how big the problem is and what sort of inheritance pattern it follows. Don't sell any pup who manifests a heart murmur at 2 months of age. Even if the heart murmur goes away over time, do not breed any dog who has ever had a heart murmur. Siring a pup with PDA does not automatically rule out using that stud dog again, but try not to breed to a dog who has produced PDA if another equally good stud dog is available who has not produced it. Surveying the population for longevity and health problems of all kinds will turn up some surprises -health problems nobody knew existed because the incidence is so low. The Great Pyrenees Club of America has information from thousands of Pyrs on file. I am very pleased to have been a member of the Heath Information Committee while this program has developed. Participation in the program is entirely voluntary and all names are kept entirely confidential. The Pyrenean Shepherd Club of America is starting to compile the same sort of data base. The American club found that the average lifespan for a Pyr is 11 years, with some individuals living to 18. The most common specific cause of death is cancer. Bone cancer and cancer of the reproductive organs are the most common kinds of cancer. Personally, my dogs have had virtually no cancer. However, recent veterinary studies show that spayed/neutered dogs have a much lower incidence of cancer, and I require pet buyers to spay or neuter their dogs and I spay/neuter my show dogs after I decide they will no longer be used for breeding (I know this is an American idiosyncrasy that many French will never understand). The vast majority of owners rated their dogs' health as good or excellent. In general, we thought the health of our breed was good, but now we have the statistics to back it up and we know just exactly what the problems are. All this knowledge does change the breeder-buyer relationship a bit, but I think the change is good. Both breeders and buyers are better educated. No one can say to a buyer that the breed or any one bloodline produces absolutely no genetic defects. On the other hand, no buyer can be absolutely shocked when a puppy turns out to have a problem. I am able to tell my Berger puppy buyers that there is something like a 5% chance that his pup will have hip dysplasia, and about a 5-8% chance that it will have epilepsy. Responsible pet owners who intend to take care of their puppies usually weigh these figures and decide they like the approach. Buyers who believe the myth that Bergers are so naturally healthy that they don't require vaccinations and can live for months at a time eating only grass (as one American book proclaims) are not sensible people and I, for one, don't want my puppies living with people who are not prepared to take care of them. Beyond this, I guarantee my puppies. If the pup develops a genetically-based condition which prevents it from being a satisfactory companion, I will give them a new puppy --provided I am convinced they have raised the puppy properly. I do not require them to return the original dog. After all, what would I want with a dysplastic or epileptic dog? I have replaced several dogs over the years, but not so many that it has ever become burdensome. In conclusion, I urge you to x-ray your breeding stock for hip dysplasia. I think you'll be surprised at how well your dogs do. And I urge you to conduct a confidential survey of as many breeders and owners of all 4 breeds as you can. I'd love to see the statistics on how healthy our breeds are! Best wishes, Patricia |