Breeding is doing a selection of the best dogs and bitches of a generation, for the transmission of their genes to the next generation. The objective is the preservation of the breed and improvement. The best dogs and bitches are those that conform to the breed standard, that have the best health, and that carry the best genes.

Some breeds already have several genetic tests ready that allow them to improve the genes passed on to each generation. For the Westie, the CMO test is the first major genetic test available.

The management of the CMO gene must consider the number of livestock of the breed in the country concerned, the frequency of the pathogenic gene in the livestock and the essential need to maintain the genetic diversity of the breed.

The WHWT breed is the most affected of the three breeds of terriers carriers of this gene, but it is also the breed which has the largest population, which is an advantage in this type of situation. On the other hand, its low heterozygoty makes our breed very sensitive to many genetic diseases, and there is a urgent need to preserve the gene pool.

Taking the entire population of non affected WHWT, about a third of them could carry the CMO gene, in one or two copies (this considering the sample of the Swiss study as representative of the whole breed).

It is not desirable to remove so many carriers from reproduction at once because that would be dramatic for our breed , but it is desirable to do a first selection among these carriers.

With this test, the CMO gene can be greatly reduced or even eradicated in a few generations if breeders are willing to invest their efforts and money, and to cooperate. Solidarity between breeders will be a key point for fighting this gene.

-1- The test allows to push aside CMO-2 dogs from the livestock, these dogs are at high risk of developing the disease. The team of the Bern Genetics Institute does not recommend their use in the three affected breeds. Even in the rare case that they do not develop clinical CMO, they should be definetly excluded from reproduction because they transmit the CMO gene to all their puppies.

All their puppies therefore are at risk of developing the disease.

 

-2- The test allows the use of dogs carrying one copy of the mutation of the CMO gene (CMO-1). The team of the Bern Genetics Institute recommends selecting the CMO-1 that have the most value, and to marry only to CMO-0.

50% of the puppies of such marriages will be CMO-1, that is to say at low risk of developing the disease.

These breedings are essential in order not to lose the precious genes carried by many CMO-1 dogs that could be of great importance for the future of the breed.

In this case, it seems necessary to test the puppies born from such unions and to inform the future owners of CMO-1 pups of the risk of developing the disease (although the risk is low) and to discouraged breeding with them, even if they do not develop the disease.

The CMO-0 puppies of such marriages should be used first to pass on their genes to the next generation.

 

-3- If for a reason or another, a breeder is forced to breed his female CMO-0 with an untested male, it is advisable to early test all puppies, to ideally keep only the CMO-0 for the next generation... if there are ...

In practice, the lines are not all affected by the gene the same way.

Those with less than 20% of carriers can more easily be cleared of the gene in one or two generations. For breeders who have more than 30% of carriers, it may take 2 or 3 generations to eliminate the gene, maybe more.

The difficulty in the management of a pathogen mutated gene, is to eradicate it without impoverishing the gene pool of the breed, it is a particularly acute need in our breed which has a relatively low genetic diversity.

Prolificity of bitches is also a limiting factor for the selection of healthy pups for the next generation.

For example, if a breeder marries a CMO-0 to a CMO-1, and obtains a litter of three puppies, on which he intended to keep a female CMO-0 for the next generation ... in every litters, the probability for a puppy to be a female is 50%, and for every female born the probability to be CMO-0 is 50%.

The probability of having a female CMO-0 in this litter 50% (probability of birth of a female) x 50% (probability of inheriting two clear genes) = 0.5x0.5 = 0.25 = 25 % which means one in four puppies....

In a litter of 3 puppies, 0.75 chance (less than one chance)
In a litter or 5 puppies, 1.25 chance
In a litter of 6 puppies, the chance rises to 1.5
In a litter of 8 puppies, the chance rises to 2 CMO-0 female puppies

It will be profitable for the breeder to use a bitch with a good prolificity to increase his chances of birth of a female CMO-0 in this type of marriage.

 

-4- The responsibility of the breeder is engaged by this test:

- All serious french breeders of the breed are already aware of the existence of this test, which was chosen by the Club of ATE for selection schemas.

- If a breeder decides not to use this test, whatever the reason for this, he takes the risk of selling pedigree CMO carriers puppies (CMO-1 or even CMO-2), and he takes the risk to face legal responsibility.

               ..if the puppy purchaser is an individual, and that the puppy develops the disease, it may turn against its vendor.

               ..if the buyer had expressed his desire to breed the puppy when adult (a fortiori if the buyer is breeder) and if the puppy gets sick of CMO, or if the buyer tests the puppy and discovers he is CMO-1 or CMO-2, it could result in a legal action against the seller.

               ..Only a purchaser buying a puppy from untested parents, if  he was dutifully informed in advance of the situation in a written document, won't be able to turn against the seller.

 

-5- These tests represent an investment for the future for breeders. If they force themselves to perform in parallel the DNA parentage tests proving their breeding are true, when all their livestock will be CMO-0, the next generations out of these CMO-0 will no longer need to be tested because their ancestry back to these dogs will be certified clear by parentage testing regularly implemented.

Remember that these progeny tests (which are not simple DNA identifications but are compatibility testing with parents) are the only guarantees of the validity of the pedigrees.

 

Conclusion: Genetic tests combined with parentage testing are the future of our breed.

I hope that one day soon, genetic tests will allow us to solve other endemic diseases to which our breed is predisposed like Atopic Dermatitis, Démodecic mange, luxated patella, congenital cleft palate, congenital liver shunt, Legg Perthes Calve, Pulmonary Fibrosis, chronic gingivitis, segmental uterine aplasia and other abnormalities leading to dystocia...