Are Pugs Breaking the Rules of Mammal evolution?

Many of you might have heard of Canine Degenerative Myelopathy.  It is a disease that can affect our dogs and has caused heartbreak for many owners for many years now.  The primary symptom of this disease is hind limb paralysis in older dogs. The condition is often non-painful but the spinal cord degenerates as they age and this leads to the paralysis of the hind limbs.  Unfortunately, this disease is fatal and is not only distressing for the dogs but also for owners.  

Linked to the genetics of the dog, Degenerative Myelopathy is inherited from the parents.  It occurs most commonly when the gene coding for a protein that destroys what’s called “free radicals” ceases to work.  Free radicals are molecules and in this case they are bad. In Degenerative Myelopathy the protein that usually acts as a natural defence mechanism from these free radicals does not work. This means that they are able to reproduce to excess.  Too many free radicals like this leads to cell death and this in turn leads to many degenerative diseases.  In order to determine if your dog is at risk of degenerative myelopathy you can have testing carried out on the parents of your dog via laboratories.  This is a test that you should check the parents have had when purchasing a brachycephalic dog breed for the first time, as many brachycephalic breeds are subject to this disease.  But of course our main question for this post is what is pug myelopathy?  Is this not the same as Degenerative Myelopathy?

What is Pug Myelopathy?

Pug Myelopathy is a very newly described disease.  Other names for this disease include “Pug Constrictive Myelopathy”, “Pug Facet Hypoplasia” and “Pug Subarachnois Diverticulum”.  A frequent word in many of these titles you may have noticed of course is “Pug”.  That’s because this disease is specific to Pugs and unfortunately has been bred into the breed over time.  It is the most common cause of mid-back spinal cord problems in Pugs and for many years was confused for Canine Degenerative Myelopathy.

However, they are not the same disease!  Pug Myelopathy is caused by a neurological deficit that develops due to either degradation or abnormalities of the spinal vertebral bones – these are the individual bones that form the puggy spine.  These bones may have either started slightly imperfect or have degraded over time. Scientists are still trying to figure which it may be. This in turn affects the nervous system either through related damage to the spinal area or compression of nerves in that area, which then leads to weakness in the back legs and sometimes paralysis.

But there is hope

Whilst degenerative Myelopathy has a poor prognosis often leading to complete paralysis and death, scientists are still learning about Pug Myelopathy and the consequences.  The differences in the diseases could mean that this disease may not have as fatal results for worried puggy parents.  Pugs with this disease have been known to live a usually pain free long life so long as they have good nursing care.  A fantastic website for those looking for how to nurse a paralysed dog is by Hindy Pearson. Hindy’s experience with elderly dogs sparked the development of her own blog “Caring for a Senior Dog”.  She even has a whole section on mobility issues so if this is a concern or you then please do take a look it has some wonderful tips from a lovely individual with lots of experience in the field.

In general it is important that Puggy owners become aware of this disease and the Pug Dog Club of America has issued a warning to look out for it in elderly pugs and seek veterinary care if symptoms occur.  In the meantime Michigan State University is at the forefront of research with funding from the Pug Dog Club of America. Unfortunately, until more is known there is no consensus among vets about the best way to treat it, but I’m sure the scientists at Michigan State University are working their hardest to find out. 

Be aware of imposters!

It is also important to mention that there are many other diseases that affect pugs that can cause mobility loss in Pugs. Such as hemivertebrae - an awful condition due to the malformation of the dogs vertebrae often found in young dogs, sudden intervertebral disc disease, slipped disc disease, cord tumour or spinal arthritis.  It is therefore of course recommended to go the vets with any symptoms such as change in walking, loss of bowl control, or any behavioural changes in your puggy at any age to check out what it could be.

Are Pugs SUPER evolved?

An fascinating brand new study published just this year (written by scientists including Noel Fitzpatrick, of whom many may know of from the “Supervet” TV series) questioned how Pugs may well be “breaking mammalian evolutionary constraints”.

In the world of evolution the number of vertebrae (bone segments in the spine) in mammals is almost constantly 7.  This does not change regardless of the animals neck length and it is suggested that any change in this number of vertebrae is usually fatal.   Simply put: 7 vertebrae = healthy mammal yeay! Any change = oh dear not so healthy mammal!  

But…….what if a mammal was to be born with something different to this. In humans a change in this number has been found to be associated with fatal traits and in general it’s not usually a good thing. But what about the SUPER PUGS! It has been found that Pugs have actually survived even with a variation from this normal number of vertebrae. However, whilst Pugs are surviving this deviation from normal mammal evolution, this change is leading to increasing mobility issues in the breed.

A further study also looked into Pugs and their abnormal evolution.  After comparing French Bulldogs, English Bulldogs and Pugs together (a total of 271 dogs) they found that pugs appear to have specific breed characteristics that give them anatomically different vertebrae than other breeds.

These studies are interesting because it really highlights how pugs are quite a special breed….I mean we all already know they are special….but that they are evolutionarily unique?! Perhaps THATS why they have those quirky personalities? 

Whilst I am discussing this subject light heartedly – it is important to consider that this IS a possible concern – whilst pugs are surviving these vertebral abnormalities it is now said that 1 in 3 pugs will have walking issues. I am by no means putting people off pugs, they are a wonderful breed, I myself have one, but if anything perhaps this post can encourage those looking for a pug puppy to check for testing for any degenerative issues to avoid any issues in your pugs adult life.

 

References

Bertram, S., ter Haar, G. and De Decker, S., 2018. Caudal articular process dysplasia of thoracic vertebrae in neurologically normal French bulldogs, English bulldogs, and Pugs: Prevalence and characteristics. Veterinary Radiology & Ultrasound.

 

Brocal, J., De Decker, S., José‐López, R., Manzanilla, E.G., Penderis, J., Stalin, C., Bertram, S., Schoenebeck, J.J., Rusbridge, C., Fitzpatrick, N. and Gutierrez‐Quintana, R., 2018. “C7 vertebra homeotic transformation in domestic dogs–are Pug dogs breaking mammalian evolutionary constraints?” Journal of anatomy.

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