The OFA and the Role of Canine Health Databases
by Eddie Dziuk, originally published by and reprinted with permission
of Dog News
The decision to breed dogs brings with it a host of responsibilities.
Responsible dog breeders properly house, feed, and care for their dogs.
They provide proper socialization for their puppies, and go to great lengths
to screen perspective buyers, and place their puppies in good homes. Responsible
dog breeders do not allow their dogs to end up in rescue organizations,
they maintain a lifelong commitment to the animal. The list goes on, these
are but a few of the responsibilities that separate the serious, responsible
dog breeder from "backyard" breeders and commercial operations.
Another
area of responsibility assumed by the dedicated breeder is a commitment
to health issues. This commitment to overall canine health goes beyond
providing puppies with their first shots. It goes beyond a concern of
keeping the puppy well until the warranty after the sale has expired.
While no one, commercial breeders included, wants to produce puppies that
are deaf, go blind, seize, or are lame, the actions taken up front to
minimize inherited diseases help define what makes a person a serious,
dedicated, and responsible breeder.
Conformation traits, working ability, and temperament are routinely factored
into the selection criteria leading to a particular breeding. Health concerns
need to play a similar role in these decisions. The prioritization and
balance of these selection criteria contribute to making dog breeding
an art, not a science. However, even as an art form, there is a scientific
component. Often, the most successful breeders are those who have been
working with a long line of particular dogs. They have personal knowledge
of generations of dogs within the pedigree. They have experienced first
hand the dominant traits, both positive and negative, which certain dogs
carry. In short, they have data; information, which allows them to make
more informed breeding decisions.
The role of canine health databases is to apply the same concept of knowledge
to health related issues. They capture health information on individual
animals and allow breeders to make more informed breeding decisions by
including health concerns in their mix of selection criteria.
In recent years, a number of DNA tests for specific diseases have been
developed. These tests remain the "gold standard" since actual
genotypic information is derived. Test results, their submission into
a health database, and the applied use of the database can have significant
results in reducing the prevalence of a disease. PRA in Irish Setters
is an outstanding example. For years the Irish Setter Genetic Registry
maintained statistics on test matings in order to identify carriers of
the disease and eliminate them from the breeding pool. Their data assisted
researchers in identifying the actual disease causing mutation and ultimately
led to the development of a DNA test for PRA in the breed. As a result,
testing along with applied use of the database has greatly improved the
health of the breed.
Unfortunately, most inherited traits, including inherited diseases, are
probably polygenic. They have a complex mode of inheritance influenced
by multiple gene pairs. To date, no DNA tests have been developed to identify
the specific combination of mutant genes responsible for any polygenic
disorders. Therefore, decisions regarding a dog's suitability for breeding
purposes rely on phenotypic evaluations. The complexity of polygenic traits
results in a wide range of expression, from least to most desirable. It
is the reason why two dogs of ideal conformation may produce offspring
less than ideal, and the reason why the mating of two dogs that are phenotypically
normal for a disease may produce affected offspring.
When dealing with genetic unknowns, it is difficult to control the incidence
of a polygenic disease. Phenotypic evaluations allow us to make assumptions
on the dog's genetic makeup. However, too often, breeding decisions are
based purely on the potential sire and dam's traits. Although progress
towards a desired outcome can be achieved in this method, it will almost
certainly be slow and result in surprises along the way. This is where
health databases can play a significant role. As the database is populated,
incorporating information not only on the parent's phenotype into the
breeding decision, but phenotypic information from close relatives such
as siblings, half siblings, aunts, uncles, grand-sires, and grand-dams
becomes possible. This allows breeders to make a more accurate assumption
regarding the potential sire and dam's genotype, and allows them to apply
greater selective pressure to produce desired and avoid undesirable traits.
At the heart of the OFA's quest to assist breeders in lowering the incidence
of genetic diseases are the OFA databases. When the OFA was formed in
1966, one of its main objectives was to "advise, encourage, and establish
control programs to lower the incidence of orthopedic and genetic diseases".
This objective remains firmly in place today. The databases of the OFA
give breeders access to the health screening results of hundreds of thousands
of dogs, allowing them to increase the selective pressure to produce healthy
dogs free of inherited diseases.
The OFA's original interest was hip dysplasia. This continues to be a
major focus of the organization today. However, in recent years, scientific
advances and the enhanced ability to diagnose heritable diseases have
led to the development of several additional databases. These include
databases for elbow dysplasia, congenital cardiac disease, autoimmune
thyroiditis, patellar luxation, a number of databases based on breed specific
DNA tests, and the most recent additions, legg-calve-perthes (LCP) and
sebaceous adenitis (SA).
The hip dysplasia, elbow dysplasia, and legg-calve-perthes databases
are based on radiographic evaluations. Since radiographic interpretation
and application of diagnostic criteria can differ among veterinarians,
the OFA offers a solution by providing experienced, consistently applied,
specialist interpretation. The OFA maintains a pool of approximately twenty-five
independent, consulting radiologists. Each is a board-certified Diplomate
of the American College of Veterinary Radiology. For hips and elbows,
three randomly selected radiologists from the pool evaluate each radiograph.
Hip joint conformation is assigned one of seven phenotypes: Excellent,
Good, Fair, Borderline, Mild, Moderate, and Severe. Elbow conformation
is graded as Normal, or Grade I, II, or III Dysplasia. The final OFA grade
is based on a consensus of the three independent opinions.
The remaining OFA databases differ in that the actual evaluation is performed
by a source outside the OFA. For the patellar luxation and congenital
cardiac databases, an attending veterinarian performs the evaluation.
The veterinarian must have the advanced training necessary to perform
an accurate diagnosis, and the OFA highly recommends that board certified
specialists perform these examinations. For the thyroid database, the
evaluation is based on laboratory assay performed at one of seven approved
OFA labs. The SA database is based on skin punch biopsies evaluated by
approved dermapathologists. And finally, the DNA databases are based on
results from specific laboratories licensed to perform the tests. The
OFA's function with these soft tissue databases is to develop consistent
diagnostic test protocols with veterinary experts, and offer breeders
the databases in which to register the test results.
The common thread among all the databases remains the OFA's original
objective to establish control programs to lower the incidence of genetic
diseases. However, to be a useful tool, breeders and owners must acknowledge
the value of such databases, and embrace the submission of data. With
over 800,000 studies on file, the OFA has the world's largest data bank
on canine hip evaluations. Most breeders who contribute to the data and
use the database in their selection criteria have seen improvements in
the health of their dogs. Although some information is better than none,
for the newer databases breeders and owners must remember that it may
take years for the database to become populated with enough information
to allow the type of in depth pedigree research that is the goal of the
databases.
The last few years have seen a great deal of focus and criticism on the
practices of commercial breeders. Within the fancy we are quick to differentiate
ourselves, calling ourselves responsible breeders striving to preserve
and improve the breed. However, the term responsible breeder is one that
is earned, not assigned based on number of litters bred, or mere participation
in AKC events. Complacency over health issues, especially when in pursuit
of the blue ribbon, equates to irresponsibility. As responsible breeders,
we must recognize health issues where they exist, educate ourselves on
the issues, and incorporate health issues into our breeding selection
criteria with a specific goal of reducing inherited disease. In addition
to the OFA, canine health databases are maintained by CERF, PennHIP, parent
clubs, and by several leading research institutions and universities.
All breeders are urged to breed responsibly and use these tools for the
improved genetic health of our purebred dogs.
