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IVDD Genetics for Idiots…sorry, Dummies….well…me.


3 IVDD Warriors living the good life


I could easily write a very structured "how to" guide on the genetics that influence IVDD, but if I am honest I struggle to read beyond the first few lines, it bores the pants off me! Let alone absorb that information....ouch and yawn combo! So, my apologies to those genetic guru's out there who would really rather I didn't put my unique spin on this, but this is for those of us who struggle to get it. Our brains, like our DNA all differ, and sometimes, a little bit of chaos can be easier to process. Perhaps if we understand it, we will understand in a better way the things we can do to prevent it in the first place - or at least try!

 

Conformation...i.e their shape!


We frequently see people comment that if dachshunds were bred for longer legs they wouldn’t get IVDD, but there’s a small problem with that.

a)        If they had longer legs they wouldn’t be dachshunds  (I am referring to the proportions set out in the breed standard, which hasn’t changed, but peoples interpretation of it may have!)


b)       Longer legged breeds DO get IVDD!


Its not about the length of their legs, but about their genetic code.



Just to add to my gripe, whilst I am here…THEY DO NOT HAVE LONG BACKS, the short legs give the appearance of that but they have short legs!  Can we please just get that right!



The dictionary definition of chondrodystrophic is….oh eck, I’m not copying that!  I’m trying to keep this in easy speak…..basically a disturbance in the development of cartilage (primarily of the long bones (i.e. legs/arms) resulting in dwarfism). Dwarfism is characterised by short height (in humans a lack of growth in the body, arms and legs or (more relevant) a disproportionate short stature where the arms and legs are particularly short.  Even in humans, it does not describe a long back! In fact it suggests the opposite!


Think about our friend Peter Dinklage from Game of Thrones….long body? Or short legs? (Sorry for any people offended by the comparison, it comes from a place of love and learning.) Interestingly in humans there are over 400 known types of dwarfism caused by varying genetic mutations……but before I disappear down that interesting rabbit hole, I’ll try to stay on topic!  (400 though!! WOW!)

 



These breeds are all genetically prone to IVDD (there’s probably more):

Australian Shepherd, Basset Hound, Beagle, Bichon Frise, Boykin Spaniel, Cavalier King Charles Spaniel, Chihuahua, Chinese Crested, Coton De Tulear, Cocker Spaniel, Dachshund (Long haired), Dachshund (Miniature Long Haired), Dachshund (Miniature Smooth Haired), Dachshund (Miniature Wire Haired), Dachshund (Smooth Haired), Dachshund (Wire Haired), Dandie Dinmont Terrier, Entlebucher Mountain dog, French Bulldog, Goldendoodle, Jack Russell Terrier, Labradoodle, Maltese, Pekinese, Pinscher, Poodle (Miniature), Poodle (Standard), Poodle (Toy), Portuguese Waterdog, Pug, Rat Terrier, Retriever (Chesapeake Bay), Scottish Terrier, Sealyham Terrier, Shih Tzu, Skye Terrier, Spaniel (American Cocker), Spaniel (Clumber), Spaniel (English Springer), Welsh Corgi (Cardigan), Welsh Corgi (Pembroke), Yorkshire Terrier.


Crazy right!


I’ve even seen dobermanns and danes show similar symptoms…..but obviously….they don’t have short legs (there’s a thought for the scientists…off you pop, go look at that one!)

 

It is important to consider our awareness of IVDD in comparison to other illnesses, we promote it within the breed to raise awareness, and obviously because of their shape people talk about their length….their long backs cause it (nope!) 


There are other illnesses that plagued our breed, but thanks to an extremely proactive breed health team at Dachshund Health UK DNA tests were developed – PRA, Laforas for example, alongside eye screening programs.  We need the same commitment to IVDD from the whole community.  Dachshund Health UK are the charity fighting the cause, we need to champion them and any other researchers who are fighting the good fight! Have a gander - https://www.dachshundhealth.org.uk/

 

With help, I am going to try and simplify the genetic jargon.  Hopefully, if I understand it, it will help you to as well.  Everyone knows genetics HURTS MY HEAD! 

 

The genes....... You know the vet guru's compare a disc to a doughnut, and the disc material as the jam......well on that theme, the flavour jam is the genes, and the parts of the jam that give it the flavour are the bits that make up the flavour....clear as mud? Right?


But from that little analogy you can see how many elements have to come together to make the ideal fruit, for the best jam, for the tastiest doughnut (and thats not including the flour, the putting together of that gooey goodness either) (who else is peckish now?)


One thing to really pay attention to is the CDDY (I translate that later) gene causes IVDD but it doesn’t CAUSE disc herniation, it definitely increases the risk though, hugely!  Having IVDD (Disc disease) increases the risk of the disc herniating (pop) but it doesn’t guarantee they will get it (which is why there is such an emphasis on reducing risk factors!)


I am going to keep it as simple as possible so those of us who are not genetically minded can get an idea, and I hope I explain it correctly, but this will mean those who are genetics savvy may get irritated at me leaving bits out. I only plan to look at the influence on the actual dog…not its offspring to be clear.


I really hope I get this information correct, but I have double checked with people who's knowledge on this is far superior to my own!


The jargon explained.....for my brain anyway! (Yea, its a bit yawn!)

You may hear these phrases bounced about – I am going to need them later – so here’s my definitions (my brain remember!) (Yes, I know, its like being back in high school – sorry!)

Genotype – things we can’t see – the ‘thing’ that gives the things we can see.

Phenotype - things we can see (height, hair colour)

Autosomal dominant – Basically – there is a 50% chance of passing it down from each parent.

Semi dominant – (also known as incomplete dominance) is where both versions of a gene contribute to the outcome, so they could have one or the other, or they could have both.

Alleles– are like different flavours of a gene.  If you think of a gene as a receipe, the alleles are variations of the recipe. They are the secret ingredient that make us unique.

Normal = Normal (I think we all get that.)

Polygenic – a characteristic which is influenced by 2 or more genes.


And the main genes we are looking at in dachshunds:

Dogs who have chondrodysplasia (shortened to CDPA) have short legs.  This characteristic (phenotype) is seen in breeds like dachshunds (and corgis).


Chondrodystrophy (shortened to CDDY) is caused by a different ‘thing’ or mutation to chondrodysplasia which also includes a short legged characteristic (phenotype) AND abnormal premature degenerations of the discs (i.e. Invertebral Disc Disease (IVDD)).  These discs are the ones that “pop” (or herniate). Dogs that carry this gene, are at increased RISK of a herniated disc, but doesn’t always mean they will get it. If you look at the UK Population most, if not all dachshunds carry this gene – of them, how many suffer with a herniated disc? This is the problem gene!

 

There are more, and there are other codes out there, but for now, me and you don’t need to worry about them….well, we might do but I’ll save that for a follow up when my brain isn’t hurting after writing this!

 

 

Ok, now lets look at how the gene tests might look. (I’m not going to go into how it may be passed on.  All breeders should be researching that themselves! I am simply looking at the basics of our pets!) (But, basically if the parents are not N/N there is a predicted 50% of the litter that will carry the genes).

 

Chondrodysplasia (CDPA) affects the development of cartilage growth plates.  It is responsible for short legs (NOT IVDD, although research suggests it makes them susceptible).  CDPA is autosomal dominant (see my definitions above), the dogs only need one copy to be affected.


N/N is easy right.  Dogs with this genoptype will not have CDPA, (the short legged characteristic)

N/CDPA genotype – will have shorter legs in comparison to the ones who are N/N 

CDPA/CDPA will mean they have shorter legs


Remember, this, CDPA, is the gene that causes short legs….NOT IVDD


Now, next we have Chondrodystrophy (shortened to CDDY).  CDDY affects skeletal development.  Its the gene that causes short legs AND ABNORMAL PREMATURE DEGENERATION OF INVERTEBRAL DISCS (i.e. IVDD).  I 'shouted' that as disc generation is completely normal with age - in any species!  If you had an MRI scan in your 20’s and again in your 40’s you would see some degeneration of your discs.  Some of us (lucky me) have that earlier than others.  The key here, is the degeneration is abnormal and premature! (which is why the at risks age are between 4-7years old)

 

Sorry, side tracked, here’s the catch with this gene (CDDY)…..whilst this gene increases the risk of herniation……its not a guarantee for or against the disc going “pop.”


Again, dogs with N/N do not have this gene, and are not at increased risk of IVDD. 

Dogs with N/CDDY will have shortened legs and IVDD,  and are at increased risk of a disc herniation.

Dogs with CDDY/CDDY genotype will have shorter legs and IVDD, and an increased risk of disc herniation (pop). 


I hope this is making sense.

 

So whats the problem?


Well, basically, in the UK most if not all, of those tested anyway, dachshunds carry the IVDD gene. Several genes increase the risk or development of IVDD (jargon = heritability is polygeneic).  But researchers are working hard to identify whether there is a main gene which leads to herniation.

 

Basically as you can see, its not basic.  But there are several genetic codes (remember the spiral DNA staircase from Biology class) that contribute to IVDD, its not just one thing that points to it, which is why finding a “cure” is so difficult. 

 


Ok, so what about X Rays?

We all know X Rays in diagnosing IVDD are pretty much useless, but can they help prevent IVDD in future generations? (They won’t help your dog, but may give you an idea as to whether or not they may get a disc herniation.)

alamy,com

Screening through X Rays which are then analysed by suitably qualified and experienced people does show a strong connection between a higher number of calcifications and disc rupture.  It shows a higher connection than is seen with screening in other breeds for hip and elbow dysplasia.  They have found dogs with more calcifications are more likely to have puppies with more calcifications, and thus are at higher risk of IVDD because the bones are more fragile. I speculate that location of the disc has an influence too, but again that’s speculation.  (It’s not perfect, sometimes dogs without calcifications do get herniations. Which makes me wonder if there is another influence at play.  A study for the scientists I hope in the future.)


In Denmark IVDD Back screening is mandatory and they have already started to see a reduction in the number of disc calcifications and herniations. So we have a good idea that it works.  But in the UK, breeders are resistant.  They ask for evidence, they get it, yet its not good enough!  Why? Yes, I appreciate its not definitive, but until more people do the screening, how can we provide that evidence?

 

So in an ideal world, how do we stamp it out?

I think (and remember I’m getting this information double checked, so if this sentence is still here, it is accurate)


IF we can eliminate the CDDY (Chondropdystrophy) gene from dachshunds we stand a great chance of dramatically reducing the occurrence of herniations caused by IVDD.  Whilst CDPA does increase susceptibility it doesn’t predict IVDD.  If the focus is on one rather than both we could hope to see a dramatic reduction in dogs being paralysed. 

 

HOW?

Well, the scientists are doing their part.  There are studies all over the world, particularly in Europe (including the UK) who are doing their best to identify the causes of IVDD alongside trying to find easier ways to resolve the issues associated with herniation (pop).


Breeders have the power! Which means potential owners have greater power to influence things! THE BUYERS DICTATE THE MARKET! (You are in control!)


In my opinion, I do think we should continue to DNA test breeding dogs, accept we are likely to have both genes, but if you don’t test you won’t know if one of the dogs you have doesn’t carry that gene! If we can identify those who don’t carry it, or those who only carry part of it, we may stand a chance of selectively breeding it out.  YES, I agree that will take a long time to carry out, but most of us aren’t in it for the now, we all are invested in the breeds future…..or we should be.


We should be screening as routine, and whilst current results suggest those with 2 calcifications do pose an issue, we can’t eliminate from breeding programs as yet, but we can avoid those who have 4 or more. It gives us a starting point (that’s my opinion anyway.)

 

BUT, as owners we can do our part to reduce the risks.

  • Buyers – go to a breeder who prioritise health before ego.  Someone who is doing their very best to reduce the risks.  Someone who screens. Someone who does everything they can over several generations to reduce the risk.

  • Weight – ideal weight, not fat, not skinny, but fit and active.  Go by body condition rather than the scales.

  • Exercise – keep them fit, but exercise them appropriately to their age.  Make sure their muscles are warmed up and make sure they are prepared for that big walk.  Taking a couch potato on a 5 mile hike once a month won’t help them!

  • Neuter age – evidence suggests neutering causes various health issues, including skeletal development (not just in dachshunds) and other health issues.  Breed specific advice suggests neutering under 2 years old increases the risk of IVDD. Recent research comparing all breeds supports waiting until they are mature.

  • Diet – we are what we eat.  Make sure you investigate the ingredients of the food you feed, don’t just take the clever marketing at its word.  The commercial food industry is troublesome, you aren’t necessarily feeding them a good food. There are a lot of white label brands implying they are just for dachshunds! (They aren't!)  Look at the ingredients, compare to other products.  Does it tell you what ACTUAL meat is in there? Is it real meat? How much? What about the fillers? Are you paying a lot for rice crispies?

  • Behaviour – there is a high correlation between stress and back pain in humans.  Trying to address your dogs mental wellbeing will be beneficial regardless, but it is logical if they are always tense their muscles will not be supporting them correctly.

 (More on those risks and the research here: Dachshund IVDD - Lifestyle advice (dachshund-ivdd.uk))


And most importantly, remember, even by doing it all “right” herniations happen.  There are so many combinations contributing to the herniation of a disc.  Do you notice how I’m no longer saying IVDD, but have switched to herniation. Don't give yourself a hard time if it happens, reach out for support - there's loads of it!


IVDD is the disease, absolutely, but herniations are what cause us the problems.  Yes, the herniation is a symptom of the disease, but as owners, maybe we just focus on that part of things…..breeders should be focusing on IVDD, as ultimately…..that….is within their control to a point….more than us as owners anyway!

 

We have to do something.  With the increased popularity in the breed we are seeing more and more affected with paralysis or worse!  Together we should be working to create a future for our breed, rather than face the worry over certain breeds being so far gone they are considered to be at serious risk and thus banned.  The recent legislation proposals in Germany have flagged several breeds of concern, and discussions over the banning of dachshunds....some breeds are already banned in some countries over welfare.  If we don’t act now, it might be dachshunds, and I really can’t imagine my sofa filled with another breed…..can you?

 

 

I really hope this blog has helped you understand a bit more about IVDD genetics and got you thinking. There is so much more to it, and I really have tried hard to simplify it and make it relevant to us as owners and future owners. It wasn't an easy task and I am grateful to those who had a read over for me to make sure I was accurate in what I was saying. I am a far cry from a geneticist, and the links below will provide further research if you want to go and look.



More on dachshund genetics:



IVDD Support


https://www.facebook.com/DachshundHealthUK The force behind education and research into IVDD.

Back Talk | Facebook (Shared group with dachshund enthusiasts from around the world)

https://www.facebook.com/Dedicatedtodachshunds The best place for support and borrowing equipment for IVDD recovery (UK Only)


Please note, as always, anything I say on health should not replace the advice of a veterinary specialist.

 

 

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