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CHS month: The workings of the Hip and Elbow Dysplasia Schemes

In a series of blogs, Chief Scrutineer, Dr Jerry V. Davies, will outline the workings of the Canine Health Schemes, how they can help you as a breeder or owner, and how the schemes can provide useful health information for your pet dog.

BVA and the Kennel Club have collaborated over many years to provide the Canine Health Schemes for dogs. Whilst these schemes have been aimed at providing information for breeders to select the best stock for breeding, the schemes can also be used to inform you, the owner, as to the status of your dog so that future management can be optimised e.g. with respect to diet/weight and exercise and to flag the potential for degenerative problems e.g. osteoarthritis later in life.

In the next few blogs I will outline the workings of the Hip Dysplasia (HD) and Elbow Dysplasia (ED) Schemes, how they can help you as a breeder or owner and how the schemes can provide useful health information for your pet dog.

Health screening

We are all familiar with NHS screening programmes that may help in the early detection of diseases such as breast cancer, colon cancer, aortic aneurysm, prostate cancer. These programmes are aimed at a susceptible section of the human population. Such screening tests need to be affordable, accessible and as accurate as possible. They are not intended to be diagnostic tests.

They can flag an individual who has the potential for health problems. More detailed examination and investigation will determine the significance of the screening test. Screening for breeding is slightly different but, again, parallels with our own health can be drawn. Increasingly, screening tests for parents and early pregnancies can identify potential health issues for a new baby.

What is dysplasia?

The word derives from the Latin dys and earlier Greek dus (hard, difficult, bad) and the Latin/Greek plasia (formation).  It is a very general word and not a specific diagnostic term. In fact, there is no connection between HD and ED other than they are abnormalities of development (“bad formation”) of the hip and the elbow, respectively, in young growing dogs.

Not surprisingly, if a joint is badly formed it will function poorly and will invite secondary inflammation and pain. The body may well respond by trying to “correct” the shape of the joint. The inflammation (-itis) is what causes pain while the poor conformation of the joint will impair smooth movement and function. The end product of this process can be called osteoarthritis, a term with which we are all familiar.

Genetic or hereditary diseases

Some diseases and conditions are passed down through generations of a family and are said to be hereditary. In contrast, if I break my leg skiing that is very unlikely to have anything to do with my forebears!

Unfortunately, many conditions and diseases may have a genetic or hereditary component but may also have a number of other causative factors (multifactorial). It would be possible to quite quickly eradicate a disease that was entirely hereditary by selecting out the individuals that carried the adverse genetic information. In those diseases where genetics are a significant factor but not the whole story then careful selection will reduce the incidence of the disease but not eliminate it completely.

Hip dysplasia and elbow dysplasia are good examples of multifactorial disease. So, breeding programmes that are informed by screening programmes will have an impact but will not be perfect.

Genotype or phenotype?

Until genetic tests that interrogate the genotype (the genetic structure of an individual) have been perfected for a particular disease, the only window on the problem that we can interrogate is the phenotype (the physical structure) of the disease.

Going back to human examples, X-ray screening for breast cancer interrogates the physical structure of the individual whereas genetic tests for breast cancer, where available, will identify rogue genes even before a cancer has developed.

HD and ED screening by radiography

You will now begin to see where the HD and ED Schemes fit in. They are phenotypic tests that assess the structure of the hip or elbow. From this information, the current and future health of the individual can be considered. But as both conditions have a significant hereditary component, they will also provide some indication of the likelihood of occurrence in any offspring and therefore inform any breeding decisions.

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