01/30/17

Breeding Away from MMVD in Cavalier King Charles Spaniels

Puppy Buyers What You Need To Know about MMVD in Cavalier King Charles Spaniels

ResearchBlogging.orgThe health of many breeds was slammed in the documentary “Pedigree Dogs Exposed”, and one breed that received a barrage of criticism was the Cavalier King Charles Spaniel (CKCS or Cavs).

Heart issues are a problem in Cavs, and it can be fatal. The hearts of all mammals are made of a series of chambers and valves. It is a very synchronised organ and everything needs to work ‘just so’. During one particular condition, myxomatous mitral valve degeneration (MMVD), one of the heart valves ceases to function properly. Overtime, this puts pressure on the rest of the heart, and this leads to chronic heart failure. How individual dogs react to MMVD varies a great deal, and so prognosis after diagnosis is quite variable. The disease often progresses slowly. (If you more detail see this ACVIM factsheet.)

To understand the gravity of this problem, 37% of Cavs that die before 10 years of age do so due to MMVD. (From Swedish insurance data 1995-2006.)

Knowing that there was a problem, the Danish Kennel Club (DKCA) chose to act.

 

The DKCA Breeding Scheme

The DKCA brought in a mandated breeding scheme in 2002-2011, leading to 997 Cavs being examined in those years. Examination include asculation (stethoscope listening) and echocardiography (“echo”, sonograph of heart using ultrasounds) to evaluate the presence of murmurs in any indviidual cav. (Murmurs are predictors of MMVD progression, and have a genetic component.) Each dog was evaluated 1-4 times. There was a total of 1471 exams over the 9 years.

From my understanding, the DKCA required that Cavs be examined after 18 months of age to be approved for breeding. This approval would last until the dog is four years old and, to be bred after four years of age, they had to be re-examined and approved a second time.

To be approved, the dog had to have a MVP grade of two or less, and a mitral regurgitation murmur grade of three or less. If a dog had higher scores, they were excluded from breeding. After 2007, the criteria changed to become slightly more strict. It’s interesting when reviewing the data in this study that the largest number of unapproved dogs occurred in 2007, presumably as a result of this ‘tightening’ of regulations. While this must have been disappointing at the time, it’s a good way for the DKCA to encourage continual improvement without causing a huge reduction in genetic diversity.

The status of each dog examined became published and freely available on the DKCA website.

The DKCA would only register puppies from parents that had fulfilled the cardiac health criteria.

 

How good was the scheme?

This article, published in the Journal of Veterinary Internal Medicine, evaluated the study. Here, comparisons were made between scores of the beginning of the scheme to the end. They also categorised dogs as either approved by the breeding scheme (both dogs tested before mating), or unapproved (one or both parents unknown cardiac status before breeding).

Over the course of the study, they concluded that Cavs were at a 73% decreased risk of developing MMVD.

“A mandatory breeding scheme based on auscultation and echocardiography findings significantly decreased the prevalence of MMVD over the 8- to 10-year period. Such a breeding scheme is therefore recommended for CKCS.”

As a personal comment, I wanted to note that of the 1380 exams that met the criteria of this study, only 78 animals were excluded from breeding.

 

What would be better?

Being able to DNA test for MMVD would be brilliant, but even though we know this condition is highly heritable, DNA markers have not been established. DNA testing is not conceivable in the near future.

“Breeding restrictions or recommendations aimed at decreasing the prevalence of MMVd in CKCS have been developed in breeding clubs in different countries. The high heritability of the disease indicates that section against the disease could be successful.”

This study was retrospective, and only included animals over 18 months of age at their first examination, and excluded animals that were pregnant or lactating. Nine years is a long time, and there could have possibly be variations in scoring over time (despite this studying using clinical observers). A study with a greater sample size with less exclusions and more consistent scoring would always be better, but not necessarily highly achievable.

Interestingly, sometimes dogs can test better if there are changes in the dog. So, a dog’s heart may appear to have a murmur on one occasion, but if the dog changes body condition, heart rate, or both, then the second time the dog is asculated, it may not get the same reading. Therefore, testing dogs on numerous occasions would probably be best for consistency (but a difficult task in reality).

 

What does this mean for puppy buyers?

If you are wanting to add a Cav to your family, when talking to Australian breeders, the recommendations were made that breeders should be:

  • Having their breeding CKCS’s hearts examined annually, preferably by a specialist.
  • Not breeding from dogs that show a heart murmur at five years of age or younger.
  • Not breed any dog until they are 2.5 years old, especially if the parent(s) of the dog have murmur(s).

I asked a couple of Cavalier breeders on their recommendations, and have included them below as a starting guide for puppy buyers.

From Liz at Wandalier Cavaliers:

I think that it’s important to stress that [MVD] does appear to be random. That the level of deterioration, and the age of onset can vary greatly. But basically the later the onset, the better the prognosis. But you can have one dog with a heart murmur, and all the litter mates are fine. There’s also still no known mode of inheritance.

And from Barbara at Karhisar Cavaliers:

An important thing for those wanting to buy cavalier puppies is asking the right questions when contacting breeders. Sire and dam should both hold a minimum of current, clear heart & eye certificates from cardiologist and ophthalmologist. Breeders who are doing the official testing will be only too happy to name the relevant specialists and provide copies of the sire and dam’s health clearances.

When looking for parents who have certification, keep in mind that both parents should be cleared. In this study, there was only a significant reduction in risk for offspring if both parents were approved by the breeding scheme. Half the parents being approved is not good enough.

 

Where to for Cav breeding schemes from here?

While the results from this Danish scheme seem good, and a similar scheme in British showed promise as well, there was another in Sweden that didn’t have a significant effect. So, we can conclude that breeding schemes probably have a role in improving breed health, but exactly what the perfect breeding scheme may be is a bit of an unknown.

However, it is likely that mandatory breeding schemes are likely to be the only ones with oomph to bring about change. Schemes that aren’t mandatory haven’t yielded great results.

It’s important to note that not all heart murmurs are associated with heart disease. 6-10% of Cavs have ejection murmurs, and we shouldn’t exclude those from breeding as this would reduce genetic diversity.

So basically there needs to be further evaluation on ongoing breeding schemes to balance costs and benefits.

 

Reference:
Birkegård, A., Reimann, M., Martinussen, T., Häggström, J., Pedersen, H., & Olsen, L. (2016). Breeding Restrictions Decrease the Prevalence of Myxomatous Mitral Valve Disease in Cavalier King Charles Spaniels over an 8- to 10-Year Period Journal of Veterinary Internal Medicine, 30 (1), 63-68 DOI: 10.1111/jvim.13663

On an unrelated note, Some Thoughts About Dogs was proudly one of the Top 50 Dog Training Blog.

06/23/14

Scottie Cramp

ResearchBlogging.orgWhile reading up on CECS in border terriers, I happened upon a condition called ‘Scottie Cramp’. I was keen to learn more, and found the article “Hyperkinetic episodes in Scottish Terrier dogs” (and, more importantly, the reproduction of its text on the Scottish Terrier Club of America website).

Scottish terriers. Photo courtesy of Argowan Scottish Terriers. (Photo for illustration purposes - these dogs do NOT have scottie cramp.)

Scottish terriers. Photo courtesy of Argowan Scottish Terriers. (Photo for illustration purposes – these dogs do NOT have scottie cramp.)

 

What is ‘Scottie Cramp?’

‘Scottie Cramp’ is the popular term for hyperkinetic episodes in scottish terriers. This is a central nervous system problem that causes the hindlegs of effected Scottish Terriers to ‘cramp up’ so they kind of ‘skip’ with their hindquarters.

This condition is often brought on by excitement or exercise, and gets worse as exercise progresses. Generally a walk of 90m-600m was enough to bring about symptoms in affected dogs in this study. (However, there was one badly effected dogs who displayed symptoms after 10m.)

Usually a dog will exhibit symptoms before 18 months of age, and this condition does not seem to affect the dog’s lifespan.

 

What does it look like?

The paper does a pretty good job of describing this disorder. So here’s what they say with some added emphasis from me:

During exercise, the onset of a hyperkinetic episode was usually indicated by a slight abduction of the front legs, resulting in an arclike motion of the limbs while extending.  The back then became arched in the lumbar region, and the hind legs were quickly over­flexed and then swiftly returned to the ground.  This motion has been appropriately described as a “stringhalt” gait.

The front legs became increasingly stiff, and while walking were quickly ex­tended then flexed. In rare cases where the back was not arched, the dog walked with a “goose step” gait. Forward movement was usually hindered, and in severe cases was completely absent, resulting in the dog walking in place. Facial muscles did not ap­pear to be affected at this time…

Occasionally, when the younger dogs were running, the hindquarters would suddenly and strongly become elevated, often to such a degree that the dog somersaulted. If the inducing stimulus was continued, the hind legs became increasingly resistant to flexion, which finally resulted in a pillarlike stance, with the dog unable to walk. If the dog fell down, it would curl into a ball with its head, limbs, and tail tucked in; breathing would ap­pear to cease. The severe seizure would last approximately 15 seconds, after which the dog appeared relaxed and panting. During or just preceding a severe episode, the facial muscles were often affected, and the dog was unable to open its jaws.

None of the dogs lost consciousness during an episode, nor did they appear to be in pain. A short period of rest would alleviate the hyper­kinetic episode in most dogs, but the signs would quickly reappear if the inducing factors were not eliminated.

Here’s a video showing a scottie with this cramping disorder, and a ‘normal’ scottie:


 

What causes it?

This was a small study of only 10 dogs, but the results seem to indicate: “Excitement and fear facilitated the hyperkinetic episodes, whereas anxiety and apprehension were often inhibitory”. (Personally, I am not sure that fear and anxiety are different enough to form this kind of conclusion.)

They also found that amphetamine sulfate, when injected intramuscularly, caused symptoms within 15 minutes.

There was a lot of variation between dogs and symptoms, but it seemed that frequent exposure to the trigger, the dogs tended to build tolerance. However, no dog ‘recovered’ (i.e. ceased to display symptoms).

 

What fixes it?

As this is a Central Nervous System problem, drugs that target the CNS, naturally, are effective.

Symptoms can be alleviated by some drugs (such as chlorpromazine, acepromazine, and diazepam) injected intramuscularly. In the case of chlorpromazine, injection intramuscularly during a seizure caused cessation of symptoms within 15 minutes.

Diazepam worked to stop dogs seizing, and also to prevent seizures (given twice daily to affected dogs).

While Vitamin E has been anecdotally suggested as a preventative, this study did not find it to be effective.

 

How is Scottie Cramp diagnosed?

3 criteria for scottie cramp:

1) abnormal gait or seizures during excitement,

2) injected amphetamine should induce an episode, and

3) administering diazepam or promazine during a seizure should cause prompt remission.

 

Reference:
Meyers KM, Lund JE, Padgett G, & Dickson WM (1969). Hyperkinetic episodes in Scottish Terrier dogs. Journal of the American Veterinary Medical Association, 155 (2), 129-33 PMID: 5816228

09/26/13

Is desexing a cult?

There are two definitions of ‘cult’ (according to Google):

  • A usually nonscientific method or regimen claimed by its originator to have exclusive or exceptional power in curing a particular disease, or
  • Obsessive, especially faddish, devotion to or veneration for a person, principle, or thing.

The community’s perception of desexing fits well into both of these categories.

 

Border terrier bitch on a table at a dog show, being examined by a judge.

The weird dog show culture.

 

How is desexing a cult?

There is relatively little data on desexing. You may be surprised to hear this, considering how the procedure is so loudly advocated, but there are few long-term controlled studies on gonadectomanies (i.e. removal of ovaries or testicles) in the dog. By this I mean that desexing is quite ‘nonscientific’ in that there is little research on what it actually does (or doesn’t) do for dogs.

Despite this, desexing is claimed to have “exceptional power in curing a particular disease”.  For example, desex your dog to fix humping, aggression, to ‘calm your dog down’, to stop testicular cancer, stop mammary cancer, and so on and so on. In this way, the desexing mantra clearly fits into the first definition of ‘cult’. Desexing is a nonscientific method that has exceptional power in preventing and curing particular diseases and behaviours.

The way that the community embraces desexing could be described as obsessive devotion. The RSPCA, PETA, and even the (government run) Dog and Cat Management Board all promote desexing. The community follows suit. There is a devotion to desexing – it is loved, embraced enthusiastically, has a committed following. The community loves desexing, despite little evidence.  This obsession towards desexing can also be described as cult-like.

In this way, desexing is a cult as it is:

  • a nonscientific method claimed to have exclusive power, and
  • obsessively followed by individuals and the community.

 

Logical Fallacies

Logical fallacies allow individuals to avoid a fundamental lack of evidence. The Glossary of Logical Fallacies explains:

… some individuals will attempt to derail the [scientific, evidence-based] process by diverting the progression of the debate with fallacious arguments.  Such efforts have the intent of masking the indefensibility of a flawed theory by muddying the waters with emotive rhetoric and fractured logic, with the ultimate goal being to convince someone to believe some idea that is not scientifically valid or that they might not otherwise accept.

Logical fallacies are inherent in both definitions of the desexing cult: a disregard of evidence underlined by a devotion to desexing.  In all things desexing, there is a fundamental lack of critical thinking. Any attempt to debate desexing often descends into a sphere of logical fallacies, like those described in the graphic below.

Rational Thinking

I frequently make arguments against mandatory and default desexing.  I say things like, “but breeding causes more dogs, not just gonads” and “there is no overpopulation problem, so it doesn’t even matter if people breed their dogs” and “desexing is correlated with some types of cancer“.

These arguments are met with responses like “Rescues desex their pets, so it’s obviously good for pets” (bandwagon) and “The Dog and Cat Management Board says desexing is good” (appeal to authority).  They make strawman arguments like, “So you’re saying that no dog should ever be desexed?” and even just deny the claims all together, “It really doesn’t make sense that desexing would cause an increase in lymphosarcoma” (personal incredulity).

People make black and white arguments like “We can either have mandatory desexing or we can let everyone have a several litters in their backyard every year”, that then extend to slippery slope arguments, “If we don’t encourage people to desex, then people will breed more puppies”.

One of my big pet hate is anecdotal evidence.  “I had a dog that was desexed at 12 weeks and it lived to 15 years old and died of a stroke” and “I knew an entire dog that used to bite everyone, and it was desexed and then it stopped biting”.

The false cause, “But so many dogs are dying in pounds because people don’t desex!” and “Entire dogs bite more, so testicles clearly cause dogs to bite.”

They ask loaded questions like, “So you are okay with the number of dogs dying in pounds?” or “So backyard breeders are okay by you?”.

In all these claims there is a lack of logic, validity and reasoning. Logical fallacies are a flaw in logic. These logical flaws are overwhelming in discussions on desexing. Debates should be argued and won on factual evidence and sound reasoning – and logical fallacies are neither.

 

What to do?

Unfortunately, the very nature of a cult is that it is difficult to break one. The devotion of to the thing itself is in the very definition of cult. Indeed, there also seems to be a veneration of gonads itself within the desexing cult.

I guess the only thing to possibly do is to logically state our claims for entire dogs, not use logical fallacies, and hope that people are willing to be wrong about that. We need to demand evidence that desexing has exceptional power – evidence in the way of articles in peer-reviewed papers. At the same time, we can supply our own evidence that desexing isn’t all it seems to be.

At the same time, we need to support dog science that allows us to make more solid conclusions on desexing. When evidence becomes available, we need to embrace it – even if that potentially means changing our view on desexing. I am not prepared to personally commit logical fallacies, just as I reject those exclaimed by others.

 

Further reading:

5 Logical Fallacies That Make You More Wrong Than You Think

The Great Spay-Neuter Fallacy

Understanding Science – Logical Fallacies

Border-Wars Comment Policy (or the Disagreement Hierarchy)