2.5.14

Degenerative myelopathy in borzoi


Genetic screening – blessing or curse in borzoi breeding?
By Evelyn Kirsch (Europeanborzoi - Ischyma kennel)


Pedigree dog breeding as we know it today has been practiced for a bit more than 100 years. With this perspective, we can look back into the past to examine if these breeding practices have been advantageous or not to our dogs.

Our different dog breeds are a real cultural heritage that, in my opinion, should be maintained. Yet in some breeds threatening problems have appeared in the meantime. Some breeds are threatened by terrible diseases or by overbreeding. Many diseases that were not so common in the past now appear much more frequently. A lot of dogs are ill or so handicapped that they cannot lead an easy or carefree life, as meant to be for a dog. This is often caused by breeding programs, practiced by humans who simply accept the risks.

In my opinion, breeding practices must not be like that. The maintenance of the cultural heritage of purebred dogs must not lead to such negative impacts on the dogs themselves.

One of the reasons making the lives of many dogs more complicated are genetic diseases that nowadays can be identified by means of genetic tests. This is good news, but how should we handle this new instrument of genetic screening? Are there also risks behind it?

Recently, geneticists have discovered that most of the genetic diseases in dog breeding can be ascribed to a very narrow gene pool in that breed’s population. The result of strong inbreeding and "champion breeding" in some breeds has led to very high inbreeding coefficients—coefficients so high that the degree of relationship between the dogs of the concerned breed is similar as that between half-siblings. As one might expect, those are exactly the breeds that struggle with many genetic diseases.

There is, however, a breed well known to us that, at international level, has a relatively low inbreeding coefficient, even though, compared to other breeds, its population is very small. That is the borzoi.

Fortunately, at the end of the last century, when the first breeding standard was formulated, the early borzoi breeders determined that the borzoi is very varied in its diversity of type and that this should be and remain part of the breed.

In his article "The stages of development of the borzoi breeding", Artem Boldareff, a famous expert of the borzoi breeding at that time, wrote about the borzois at the first dog show in Moscow held in the year 1896, when different notable borzoi breeders met for that purpose for the first time: "At the first Moscow dog show the hunters saw the best dogs of the then most important breeders. Those dogs of which we say that they have the "old blood". (annotation EB: the "old blood" was the unmixed original blood instead of the "new blood" that was mixed a lot due to the foreign breeds.)

All these types didn't resemble a lot. Not only did they differ from the cynological point of view, but also concerning their work performance. But, above all, their appearance was not only different but not even similar. And yet, despite all that, they were purebred borzois and could meet all the requirements of the meticulously determined standards. When the hunters from the different Russian estates had the opportunity to compare their dogs at that dog show in Moscow for the first time, they were said to have been extraordinarily astonished. Lots of them were convinced that what they possessed was the solely correct type and that the others' dogs were incorrect. This caused immense polemics in the cynological newspapers, or better the cynological newspaper, because at that time there was only one of them. The British would have solved this issue according to Alexander's method… They would have founded a club whose majority based on a majority of votes, would have declared an arbitrary type the correct one and every other one incorrect, and would have continued breeding on that basis. We, however, were more fair-minded. I daresay that we did it more correctly, because it would have meant an insurmountable blow for the breeding of borzoi if all types had been repressed for the benefit of a single other one. Thus any progress would have been impossible right from the beginning. After all, every hunter has the right to prefer a certain type."

Later, Boldareff writes advice for breeding in the future: "When failures in breeding occur, you have to stop and you must not continue stubbornly in the same way. The breeders must prevent in any case to pick a certain type and push it through at the expense of the others. This would lead the whole breeding to a dead end out of which there would be no escape.” (source: Zuchtbuch des Allgemeinen Deutschen Windhundklubs E.V.i.D.K.H – Abteilung: Windhunde (Hetzhunde) Band VI 1931 und 1932, S. 104-111)

We obviously owe it to that former decision that the borzoi has been preserved until today in a very huge variety of types. Breeders can still follow their own type and most of the time this is approved and accepted internationally by both the other breeders and the judges.

The huge variety of types is a testimony of a huge variety of genes that are present in our breed, and, according to the modern geneticists, this is the most important thing we need in out breeding: a variety/ diversity of genes.

In the past, when we didn't have that much knowledge about genetics, the dog breeders strived for the so-called "Hochzucht.” Hochzucht meant that the dog was expected to possess the breed-specific features as homozygous as possible. Thus inbreeding became the principal tool in the work of most of the breeders. Probably we even owe the fact that we have quite homogeneous breeds at present to that method. Although we strive for a reinforcement of the desired features of our dogs and keep them homozygous, this practice will irrevocably lead to reinforcing the undesired features and keeping them homozygous, too. Genetic diseases are part of the undesired features.

Thanks to the huge diversity of types in our breed, determined by the early Russian breeders and being kept in the borzoi over many decades, we have a very large gene pool in the borzoi population. The modern knowledge that a large gene pool is indispensable for the health of any breed must press us to keep this large gene pool at any cost to spread genetic diseases. Here we come to the blessing that the possibility of genetic screening brings about.

Let's take, for example, the canine degenerative myelopathy (DM), which is a popular subject at the moment. DM causes irreversible and progressive paralysis of the hindquarters that in the end results in death. In many cases, older dogs are affected, but unfortunately there are individual cases of middle-aged dogs with DM as well. Some time ago, we identified borzoi with signs of paralysis, and by means of different examinations, proved they suffered from DM.

Today, there is a significant test for many breeds that determines whether the mutated copy of the SOD1 gene is present in the DNA sample submitted. This gene is said to be linked with the DM disease. Unfortunately this test is not equally valid for all breeds because it seems different genes can be responsible for the disease in other breeds. This is one of the reasons these genetic tests must be interpreted with caution.

Some borzoi breeders with affected dogs have spent a lot of time exploring the topic. They have found out that all the borzois they know who suffered from the disease were homozygous for the mutation and had the gene status DM/DM. Until today, here in our European area we do not know of any dog who was "only" carrier (DM/N) who later developed DM. On the basis of these findings, most of the borzoi breeders, at least in Germany, have, for the moment voluntarily, decided to have all the dogs tested for their DM-status (SOD-1 gene) before breeding with them. From now on only homozygous DM/DM dogs or carrier DM/N dogs will only be bred to clear N/N dogs in order to prevent us from producing dogs with the gene status DM/DM. DM/DM meaning that the dog has a high risk of developing DM.

But research is on-going. New evidence has emerged that the mode of inheritance of DM is not monogenic, that there are more factors involved in DM. Thus the SOD1-gene test can only be a fractional part of DM evidence. On the website of the Veterinary Institute for Molecular Genetics, "Generatio SOL GmbH" (http://www.generatio.de/index.php/de/informationen/lexikon/glossary/10/Degenerative%20Myelopathie%20(DM) you can read as follows: "This means that animals that possess two mutant genes usually are considered "affected", do not necessarily develop the disease syndromes. For sure, one or more other genes are involved which can prevent the disease from breaking out, even if the diagnosis reads "affected" for that dog.”
It has emerged that among many of the tested dogs of all breeds, there is a very high percentage of dogs who possess the homozygous mutant SOD1-gene but who do not fall ill. This is why Dr. Eberhard Manz (Generatio SOL GmbH) in the SV-newspaper from September 2013 on page 574 writes the following about dealing with the SOD1 gene test: "Unfortunately, at the moment a lack of knowledge among breeders leads to a wrongful stigmatization of SOD1-carriers. The "at risk"-animals (annotation EB: we call them DM/DM) are valuable because they carry a gene configuration in them that compensates the effects of the SOD1-mutation.”

This shows us that in fact this test is not exact. We still don't know the inheritance pattern of the degenerative myelopathy in the borzoi, but for the moment the test may serve breeders as a tool to produce only borzois that don't suffer from DM while, even more importantly, we don’t reduce our relatively large gene pool. In the meantime, however, we have to hope that research will go on and that, in the future, we will get better tools to act more effectively for our breed.
Probably here in Germany we will have the compulsory SOD1 gene test for all borzois that are used to breed, but taking into consideration the inaccuracy and the risk of a loss of genes for our breed, we should bear in mind that theoretically any borzoi can be used for breeding, no matter of its own gene status, but that not any combination of dogs can be used. But if we want to breed our DM-carrier bitch to a dog who is a carrier, too, we could use her brother or any other somehow related dog. The danger of DM would be avoided and the gene pool wouldn't be reduced. In this fashion, we can use a tool that we have been given by modern genetics. But in reality some bad things have crept in, and here we come to the curse of genetic screening.

More and more people who buy or are interested in puppies, as well as several breeders, prefer DM-clear dogs only. They believe only people who own DM-clear dogs exclusively are great. Future owners demand DM-testing from breeders before they buy puppies, even if, due to the combination of parents, no DM/DM puppies can be expected anyway. Again and again puppies are given back to breeders because the gene test that the puppy undergoes at home has proved the freshly purchased puppy is a DM-carrier, and those breeders who only reproduce with DM-clear dogs are considered the "better" breeders.

All those who act like that act against our breed. Thanks to the gene tests that we have performed in the last years we have found out that DM is present on most of our borzoi-breeding lines. Has any one of those people thought about what would happen if all those many borzois were excluded from our gene pool? It would be an enormous danger for our breed – a catastrophe! Perhaps we wouldn't have any DM any longer, but what will be next? The gene pool will be shrunk rapidly. Which genetic disease will appear afterwards because the basis of our breeding will have been reduced significantly?
What is often forgotten: DM has probably always been present in our breed, we just didn't have any genetic tests. But we have always lived with it without the feeling that our breed is ill. This might be owed to the fact that in reality the inheritance is not as easy as it seems at first sight with the SOD1-test. Most likely, not all DM/DM dogs fall ill. Furthermore it might be due to the fact that the disease's onset is usually at an older age, so that an incoordination of a rear limb in a 12-year-old borzoi is not that much in evidence.

What many people forget: our breed consists of much more than DM clears, carriers, and affected. When we only pay attention to DM in breeding, we may lose important features or virtues forever. Breeding lines that carry these virtues may also be burdened with DM. Do we really want to eliminate those virtues in our effort to eliminate DM? If we, however, handle the test correctly, we can breed an excellent dog even if he is a DM-carrier; we just have to find the suitable partner who is DM-clear.

This is why I ask you, dear borzo ifriends, let's use the genetic test for the good of our breed and not for the bad. Let's use different borzois to breed, but think as well of the combination of dogs. This is the intent of the DM test - it helps us to prevent producing DM-affected dogs without having to reduce our gene pool. A wonderful chance for our breed!
The enclosed photos show the variety of types in our breed the way it can still be found in today's show rings. It is important to preserve them.

2 comments:

  1. Anonymous2/5/14 16:00

    Excellent article!

    ReplyDelete
  2. Anonymous22/7/16 13:19

    Thank you for a very good article. As an owner of two wonderful Borzois...one is N/N, the other is DM/DM and has developed DM I agree that we should be careful not to exclude all DM carriers. It should always remain our goal to keep the gene pool of our breed as large as possible.

    ReplyDelete

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