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ELIMINATE PRA or EIC, OTHERS  BY CONTROLLED USE OF  'CARRIERS'?

Northwest Notes / LABRADOR QUARTERLY - Summer 2012

Diann Sullivan


Updates in genetic testing and knowledge about how soundness issues are inherited, CAN help us breed better dogs.  Each breeder has to decide what risks to take and under what conditions in their breeding programs, and none of us can define choices for another.  Truthful and non-emotional analysis of genetic disease is incredibly valuable to the breeder selecting dogs for breeding. I believe we need to sincerely attempt to apply updated information about genetic testing against diseases in order that our dogs have long, healthy lives on the earth and with their owners. WE make them what they are as we are choosing WHO is bred and to who. Breeders must desire to be responsible stewards of our dog's genetic heritage and therefore that our bloodlines long in the Labrador world.

In my years searching for not only excellent type, structure and temperament but genetic soundness as well, it was so difficult until the first DNA testing was available.One of the first two OPEN data registries ('AN OPEN REGISTRY makes all data on an animal available to breeders, whether the dog is physically normal or is affected with one or more diseases'), was PRA DATA started by Georgia Gooch in 1989.  Georgia is a Labrador breeder with a strong history in the breed, co-founding the Puget Labrador Retriever Club (with my husband and I and several others in the Northwest).  She published her first PRA report in 1991 and her second report in 1992. ( I remember well the confusion for breeders as the published reports gave information on AFFECTED dogs and meant then that their sire AND dam were CARRIERS.... But in the grandparent generation, no one would know WHO was the carrier... ). There was little published about HOW diseases were inherited as research was ongoing, and there WAS a feeling of 'Witch Hunting'.  At present, data is available on hundreds of PRA-affected Labradors.  Data on dogs listed in each report include clinical findings, AKC registration number, the name of the owner and/or breeder and a six generation pedigree.  A  release openly acknowledging the presence of the disease has been signed for each dog registered. In all cases, the owners of the dam and sire are notified that an offspring of their dog is in the registry and that their dogs are AT LEAST CARRIERS of the disease. Progressive Retinal Atrophy leads to blindness in our Labrador retrievers and IS inherited as an (autosomal) RECESSIVE. What about breeders who had invested years developing their lines? They didn't want to produce and sell dogs with problems...     There ONCE was a real problems for the responsible breeders trying  hard to carefully select dogs for their breeding programs, a time when there WASN'T DNA testing.

I remember well in the late 80's, that after several years of buying nice dogs, achieving championship points and earning working titles how crushed I would be at discovering they were affected with dysplasia or eye disease.  I was eventually fortunate to buy a wonderful bitch from top producing dogs with a very good history of producing sound as well as winners.  Her first breeding, after obtaining every clearance at the time per the breeder's codes of ethics, was to a winning dog close by and from an English pedigree. The male we kept from the litter became AM.CAN.CH.CEDARWOODS HARRIS TWEED,WC and I was so amazed at his multiple group placings with ME showing him ! He was OFA excellent (We didn't do elbows yet), CERF yearly and was used at stud a fair amount. Approximately two years after he was first used at stud, I received a phone call from a respected breeder who informed me that her puppy from his litter was diagnosed with PRA and would go blind ! That meant he was a CARRIER.  He was soon neutered and placed in a gun dog home and I began contacting everyone that I could find  who had used him or had his puppies from us, informing them that Harris was a carrier of the PRA gene. (I was openly chastised by those who then had their dogs 'implicated'...   This was happening to the most careful breeders at that time yet we had no DNA testing to tell us WHO were carriers and enabling us to prevent MAKING the disease (by breeding carriers together).           

DID those breeders 'dump' their dogs and go out and buy new dogs with the chance that these new dogs will have the same health problems or something worse ? All we could do was examine eyes yearly without fail even though the disease wouldn't show on exams until possibly well over age five years.

The control of genetic disease requires knowledge about affected dogs and, those that are carriers. It requires honesty and integrity on the part of breeders and owners of dogs that CARRY genetic defects and even more so, courage. The general tradition in purebred dogs is to hide defects. It sounds a bit crazy to compare but I remember as a young person the talk of many family members kept two cousins 'quiet'. One was what we know now to be Downs Syndrome  and the other was born on the family farm with the cord wrapped tightly around her neck and both were grossly retarded. This has been part of dog breeding for decades, as our beloved dogs are not only chosen by us but we become prideful as they earn winnings - They are extensions of us.

Simple Autosomal Recessive mode (way) of inheritance simply means that the defect or genetic 'disease' is not sex linked (meaning that neither males or females are directly linked to producing it), and to PRODUCE the disease, BOTH PARENTS HAVE OR CARRY THE GENE.  When the AFFECTED dog (HAS the disease), is even bred to a dog CLEAR of the gene, ALL puppies produced WILL BE CARRIERS OF THE DISEASE GENE. 

AFFECTED  X (bred to) CLEAR  =    ALL PUPPIES WILL BE CARRIERS

AFFECTED   X   CARRIER           =     50% CARRIERS / 50% AFFECTED

CARRIER     X     CARRIER        =    25% WILL BE AFFECTED / 25% WILL BE CLEAR /  50% WILL BE CARRIERS                       

CARRIER    X   CLEAR                =    50% CARRIERS /  50%   CLEAR   (ALL MUST BE TESTED FOR CARRIER STATUS......)

CLEAR     X   CLEAR         =    ALL PUPPIES ARE CLEAR OF THE DISEASE GENE

Purebred dog breeders have been challenged by genetic diseases for many years.  As canine genetic testing becomes better, new diseases are brought before us to consider their affect on our dogs.  Exercised Induced Collapse (EIC), is a newer defect many breeders are concerned about as it directly affects the function of our dogs. It is also inherited as (autosomal) RECESSIVE.  Most would do just about anything within reason to guarantee that their puppies would not develop major genetic problems.  But breeders (should) realize they need the information about their own dog's genetic status before selecting breeding partners for them.

Most dog breeders wish for an understandable guide to practical breeding that would ensure healthier dogs.  The struggle for individual excellence limited only to championships or achievements, can have harmful consequences.  The top winners become the 'popular sires' often regardless of their genetic health against breed problems we know to be real problems. These sires (more so than dams), can become the small number of elite show or field trial winners that grossly produce a disproportionate number of puppies in a breed.

Most breeders can effectively produce winners in conformation, performance events and working and hunting situations as many select top producers for winning.   We are NOT geneticists. Breeders who care to make each litter of puppies better Labradors , will search for information behind the dogs they are choosing to breed. Sharing information regarding  flaws and faults and, concerns of genetic diseases should not have to be a 'sacrifice' but a mutual exchange among responsible breeders. Each breeder has to choose to prioritize in their breeding programs what is most meaningful to them in respect to all traits, as we are each subjective for what is important to the Labrador, for buyers, and for our ultimate reputation.

Those whom I have asked WHY they quit breeding dogs over my nearly four decades often reply, “I produced dogs that had diseases that I couldn't live with. People I sold dogs to came back to me and as they told me the problems they had, that their dogs became blind or collapsed while hunting, and how much money they spent on them,  I couldn't handle it and didn't know what to do so I quit.”  No one wants to produce dogs that have or develop genetic diseases that lead to function problems, especially after the dogs have bonded with their owners and their children.  Understanding and USING canine DNA testing to know BEFORE breeding that dogs are either AFFECTED, CARRIERS or CLEAR of diseases we want to eliminate and believe to be functional problems for our dogs, is THE most important step we have had available to us in fifty years.

Whether we look for dogs to add to our breeding programs through web sites or advertising in such as the Labrador Quarterly Magazine, we will see 'carriers' offered. Remember breeding a CLEAR (or non-carrier) to a CARRIER will still produce 50% carriers for that disease. We CAN know now! IF a 'CARRIER' stud dog, for example, is so sought after for his many qualities and his tremendous production of top animals, there are two choices to the bitch owner. Find an outstanding son of his with a compatible dam's half-the-pedigree WHO IS CLEAR or should you breed to the carrier, have every puppy not selected at evaluation as show/breeding quality neutered and those who are 'choice' tested them to identify those clear and those carriers. Not all may agree but I strongly suggest rigorous selection AGAINST carriers unless there are no strongly related CLEAR dogs to the carrier to use instead.  AFFECTED dogs should NOT be bred. Breeders have more control over genetic diseases than is often exercised.

As breeders, we make selective choices for and against what we want in our dogs. We each decide what our priorities are in the structure, type, retrieving drive, acceptable movement and health issues and choices made for these traits, as FAULTS or FLAWS. Some breeders would choose to tolerate 'flaws' such as eye color, a missing tooth or something like feet and find that FAULTS (more serious traits), not to be tolerated in their  program. Over time, a breeder will  select more strongly against shorter length of neck /angle of the shoulder, small second thigh, or FOR  better coats, stronger bone, or type of head.... By selecting FOR and AGAINST specific traits in our dogs, we create and set our dog that becomes predictable in structural correctness, type and soundness.  

 With diseases that are inherited as SIMPLE RECESSIVE, those DISEASES CAN BE ABSOLUTLELY ELININATED by not using carriers......  We need sound breeding programs that are based upon selection procedures to choose FOR excellent structure, type, movement, temperament and, breed better dogs as we avoid major defects. In developing breeding programs, we must select for the overall excellent dog and not just winners at dog shows and field trials, etc.  Dogs are not BEST because of exaggerated traits; every great individual should come before specialized considerations.

Reading from the many books specific to improving breeding programs is a must resource. These are two of my favorite books for the dog breeder :

George Padgett's, “Control of Canine Genetic Diseases”   and

Successful Dog breeding by Chris Walkowicz and Bonnie Wilcox DVM

There are few solid ways for those newer to the dog sport to be guided in the right direction for a good understanding of the basic problems they will encounter.  Many established breeders are willing to serve as mentors to novices and help them enter the complexity of purebred dog breeding and, this relationship is very special indeed.

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