Degenerative Myelopathy Part 2: Should We Worry About The Hovawart's Future?

After Degenerative Myelopathy Part 1: What Can You Do For Your Dog?, we continue with part 2 about what scientists, breeders and clubs are doing, in the fight against Degenerative Myelopathy, DM.

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The news hit like a bomb shell.

"From the samples of 1,200 Hovawarts we investigated, the DNA test for the SOD1 mutation, a gene believed to be a major factor in degenerative myelopathy, showed 45% are free from the mutation, 45% are carriers, and 10% are affected."



Dr. Elisabeth Dietschi, Phd, and prof. Tosso Leeb, from the University of Bern, Institute of Genetics, presented their first result from the Research project of the Hovawart, to participants and breed clubs worldwide, back in 2012.

The numbers were dazzling, and the complete opposite of what was expected based on health statistics in the different breed clubs. Could 10% of today's Hovawarts be affected with DM? And 45% a carrier?

I wish there was a short yes or no answer to that question, but there is not.

As Dietschi already stated when she started the research project a couple of years earlier, the SOD1 mutation is believed to play a major role. But with the Hovawart, and a lot of other breeds, it is a combination of genes that play a role, and perhaps even some environmental factors as well. SOD1 on itself is not the smoking gun. From the Hovawarts tested as "affected", some did suffer from DM, but some lived a long and healthy life as well. Even some dogs that were tested "free", did develop DM at some stage in their life.

In an article from the German club "Hovawart Zuchtgemeinschaft Deutschland", HZD, some statistics were published from the club's health database, showing that from the records of 8,000 Hovawarts in their database, only 16 individuals suffered from DM. It underlined the contrast between research and breed-database quality, but also questioned how relevant SOD1 is as the cause for DM.

Back to the bomb shell. It had the affect most bomb shells have, and the clubs scattered in all directions.

Some examples. One of the Dutch Hovawart clubs, "Hovawartvrienden", HVN, now require - as they name it - "DNA testing for DM" in their breeding program. Which is odd, as we now know there is no full-proof DNA test for DM, but only testing for the SOD1 mutation, which is not the same. Just semantics? They do matter, and I will come back to that later in this post. The American Hovawart Club, AHC, started testing for the SOD1 mutation as well.

The Hovawart club of Italy took it one step further, and adopted the DM research project together with the University of Bologne, to continue further research into the causes of DM. As part of this project, they started to collect DNA samples of all Hovawarts in Italy.

Most clubs were of the opinion though, that further research is needed, before any DNA testing should take place and adopted in breeding programs, as there is too much uncertainty at the moment. Again an example hereof, from the Swiss Hovawart club's bulletin this time.

While clubs seem to disagree, let's also not forget DNA testing is not the holy grail either. Jerold Bell, DVM, Clinical Associate Professor of Genetics, Tufts Cummings School of Veterinary Medicine, wrote in his article Maneuvering the Maze of Genetic Tests: Interpretation and Utilization about the ability to test your way to health:

"It is distressing when a genetic disorder is confirmed. Positive and practical genetic counseling recommendations can be made to maintain breed lines and genetic diversity, and improve the overall health of breeds. The total elimination of defective genes will probably be impossible for most breeds. "

It is clear though, that the majority of Hovawart clubs want to prevent rigorous DNA-testing for SOD1 in breeding programs, as it is uncertain it will solve DM. It would also open the door for a huge decline of the gene pool, if we would include SOD1 test results in selecting mates. Do we really want to throw out 10% or more of the genes available in the breed, for a test that is uncertain?

When scientist have finished their research, and a test is developed that can diagnose DM, we can first answer that question. Most breeders and clubs seem to agree on that. And I like to add, when that day comes, and there is a test available for DM, not only to attack DM through selection, but also to have a plan how to introduce new genes to avoid the ever shrinking gene pool, from which we know from other breeds, eventually will lead to nothing.

As Dietschi wrote in her research:

"Like every breed, the Hovawart also has a closed population, so no new genes are being added. All dogs are becoming more closely related, even though the inbreeding coefficient is taken into account for mating. As a result, there is a trend towards homozygosity and thus a fixation of characteristics. This applies to positive traits but, unfortunately, also to negative traits."

Should we worry about the Hovawart's future? On the short term, we are still uncertain of the role DM plays in the breed and how to solve it, but at least we haven't made it worse by trying to breed our way out of problems based on a possibly inappropriate DNA test, and put 10% or more of the population in the garbage can. On the other hand, we are in the dark of how much of the breed is affected based on sound scientific data, and to be patient until more is known is a hard pill to swallow.

So far for the macro view. Which doesn't help a responsible breeder or a Hovawart family one bit. They just want healthy puppies, who have a good life, With that said it therefore does make sense for breeders in the mean time, because the SOD1 test - although a poor indicator - is the only available indicator of DM available today, to test dogs for SOD1 before breeding in an attempt to at least not to pair SOD1 "carrier" and "affected" dogs with a mate who is not "free", to reduce risk until research is finished. It is the only thing one can do, with the tools at hand.

Breeders do run SOD1 test already today, either in club regime or outside it. Returning on the subject of semantics, unfortunately the SOD1 test is by some falsely seen as an actual DM test, and there are examples of breeders running away from everything that is not tested SOD1 "free". Which would be a disaster if it is allowed to continue, as it will in practice mean - when all would do that - the gene pool will be roughly cut in half.

What about you? Do you worry about DM, and what role it can play for the Hovawart's future, either the disease, or the "cure", for that matter?

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Update: 
I earlier wrote "Also both American Hovawart clubs started testing for the SOD1 mutation.". This is not correct. The American Hovawart Club, AHC, is testing for SOD1. The Hovawart Club of North-America, HCNA, is not.
I also wrote the Dutch Hovawart club "Hovawart Rasvereniging Nederland", HRN, was testing for DM, but they brought to my attention, they are not.