High anxiety about genetic
diseases comes with the territory for anybody who is considered to be a
responsible breeder these days. In fact, if you are breeding dogs, and you
aren't worried about genetic disease, you'd better hold off on that next mating
until you've done your homework.
Canine geneticists estimate that
the average purebred dog is carrying at least 4-5 defective genes. To put it
another way, when you are looking at that gorgeous champion with normal hips
you are also looking at a dog who is carrying the
genes that can cause several types of genetic disease.
And unless his owner has a
detailed genetic pedigree on this dog, you have no way of knowing what those
disease genes are.
That champion may be carrying a
recessive gene for PRA, and if he's bred with a bitch who
is also carrying the PRA gene, the disease will show up in the puppies.
And even though he has normal
hips, he may be carrying some of the recessive genes involved in hip dysplasia. If you mate him with a bitch who
is normal but also carrying recessive genes for dysplasia,
you'll suddenly find yourself, heartbroken and bewildered, with dysplastic puppies.
"I'm not worried," you
may say, " because soon we'll have DNA tests that
will solve these problems."
That's all well and good if
researchers have developed a test for the single gene disease your line is
troubled by. But if that test doesn't exist, are you willing to wait five or
ten years for your turn to come? And that's assuming you'll persevere as a
breeder beyond the six-year average when most people give up, often because
they can't seem to stop producing puppies with genetic diseases.
Of course, we are only talking
about tests for single gene diseases. Most of the severe diseases like hip and
elbow dysplasia, cancer and epilepsy, are polygenic,
caused by the complex interplay of many genes, and no researchers have come
close to developing a polygenic gene test.
Are you willing to wait 20 years
for a gene test for hip dysplasia? Are you willing to
watch another 30 years go by with no significant decrease in hip dysplasia among purebred dogs?
Breeders in
What is the secret of this
astonishing success? Nothing more profound than the fact that each breeder made
it his or her business to find out where the carriers and affecteds
were in a dog's close family — siblings, half-sibs, offspring, parents and
parents' siblings. Using relatively simple methods, they could then predict the
risk of inheritance of defective genes in any mating.
A few breed clubs in the
Times are changing, however. In
1990 GDC (Institute
for Genetic Disease Control in Animals) established an international all-breed open registry based on the
success of the Swedish model. In the following decade thousands of breeders
began to register their dogs and to make breeding decisions in accord with the
knowledge of where the carriers and effecteds were in
a particular dog's family.
Recently, GDC started an
advocacy campaign to call for the widespread use of open registries and
appropriate breeding methods. The strong response they are getting from
breeders throughout the purebred community confirms that the demand for open
registries is increasing rapidly.
But the reality is that no open
registry, whether it is the international GDC registry, or an open registry set
up by a breed club, can be useful until it contains significant number of dogs
registered in close family groups. Detractors of the open registry concept
point to this weakness but ignore the fact that even without enough information
in an open registry, breeders can still make progress against genetic disease
by doing the legwork themselves.
What can you do?
Ø
Register your dogs in an open
registry and urge every breeder you know to register also.
Ø
Do whatever you have to do to
find out where affecteds and carriers are among a
dog's siblings, offspring and other close relatives.
Ø
Don't breed to a dog whose owner
will not supply that information.
Ø
Screen as many of your own dogs
as possible, and supply that information to buyers and breeders.
Ø
Contact your breed's health
committee, the AKC and OFA and strongly urge them to actively promote the use
of open registries.
For specific information on
breeding methods and genetic disease, start with these books:
v
Control of Canine Genetic
Diseases; George A. Padgett, DVM, Howell Book House,
v
Genetics of the Dog; Malcolm B.
Willis, Howell Book House,
Several very good articles on basic genetics for dog breeding: http://www.magmacom.com/~kaitlin/diversity/genetics.html
Copyright 2001 George Packard. georgepackard@conknet.com All rights reserved.