Labrador Health Testing

Why Health Testing?

DNA Testing

We are so lucky in our breed that diseases such as PRA (Progressive Retinal Atrophy), EIC (Exercise Induced Collapse) and HNPK (Hereditary Nasal Parakeratosis ) are now able to be eliminated in our breed due to DNA tests that have been developed for our breed along with a swag of other tests that ORIVET labs have testing for.

All our dogs have a full panel of DNA tests done - we do not rely on clear by parentage testing (CBP) only! We will only use stud dogs who have been DNA tested also. Very rarely, some clear tests have been shown to be in error, so this is why we will never rely on CBP only. Ultimately, all our dogs will be clear, but we do not discard dogs in our breeding program just because they may be a carrier - the DNA tests enable us to keep carriers and make sure we only breed to a clear dog to ensure any resulting progeny cannot be affected by the disease.

 

Hip and Elbow Scoring - CHEDS scheme

Since the year 2000, all Labrador Retrievers have been required to be hip and elbow xrayed and scored to enable resulting progeny to be registered in Australia.

Hips are scored from 0-53, while elbows are 0 - 3. A cut off limit has not been enforced on higher scores, however, I will not breed any of my dogs with scores more than 1:1 for elbows and then only to 0:0 dogs. It is very frustrating when scores are 0:0 for generations in elbows and an elbow score happens or worse elbow dysplagia happens in a puppy. We cannot guarantee that a puppy will not develop elbow dysplagia as there are lots of complex genes involved and how you look after your puppy can contribute to this also.

Hip dysplagia rarely happens in pedigree purebred Labradors these days. Once again the lower the hip score the better, with the score of  7 the current breed average. I follow the advice given to me many years ago by a very experienced UK breeder - never breed more than a combined total of 20 of the dog and bitch. 

In Australia, in 2016 a new sheme replaced the old AVA scheme and the CHEDS scheme (Canine Hip and Elbow Dysplagia Scheme)  was initiated and run by the ANKC. The CHEDS scheme has 3 specialist vets who are the only qualified vets to have xrays submitted to them for scoring. In the future it is hoped this scheme registered on the ORCHID database will be an open register for anyonel to view individual dogs scores that have been submitted.

Hip & Elbow Dysplasia are inherited developmental abnormalities in a dog’s elbow or hip joint. The hip/elbow scoring scheme only scores the parents hips and elbows for abnormalities, but does not prevent it being passed onto its progeny.  We cannot test for the gene(s) that carry this health issue as below:

Quote from the Victorian Government Code of Practice for the Responsible Breeding of Animals with Heritable Defects that cause Disease: 

"Polygenic disease – where more than one gene is involved and environmental effects can add to the severity of the condition. While the following diseases are not listed in the Schedule of the Act they are examples of diseases in this grouping that have widely divergent signs – canine hip dysplasia and elbow dysplasia. These are also conditions where simple and/or effective DNA tests are unlikely to be developed"

Our Labradors are hip/elbow scored after the age of 1 year old. The procedure is performed by a registered veterinarian. The dog’s hips and both elbows are x-rayed in an extended position. The x-rays are then sent to an accredited radiographer to interpret the results – being the ‘score’.

The following article explains the disease and how breeders can work towards decreasing the problem. It was written by Dr Wyburn who was the leading specialist in this field for many years. We used Dr Wyburn until ill health forced him to retire. We then sent our xrays to Dr Rawlinson who assisted Dr Wyburn. The AVA then decided to retire from the scheme and now we have the CHEDS scheme run by the ANKC and we chose Dr Makara to continue with maintaining consistency in scoring.
 

HIP AND ELBOW DYSPLASIA

  DR. R S Wyburn BVMS. DVR. PhD, FACVSc. MRCVS.

OVERVIEW

Canine hip dysplasia (HD) is a genetic disease which is inherited in a rather complex manner because it is influenced by more than one gene.
That is its mode of inheritance is polygenetic. HD was first recorded back in the 1930s but its incidence has increased as the popularity of breeding and showing dogs has increased. Whether this is coincidence or whether there is some relationship has not been established.
In a number of breeds the disease is present in some degree in over 80% of individuals. Because of this it is important that a control programme is put in place. The control programme should require that all individuals that are to be bred from have their hips scored and a score should be set above which breeding is not recommended.

 

Obviously the ideal situation would be to breed only with dogs that have a 0 score. However this is unacceptable as doing so could exclude most if not all of the breed. A compromise has to be reached which will allow the retention of sufficient breeding
stock but which will decrease the severity and incidence of the disease. It is up to the breed society to set standards that are acceptable for breeding.

A basic guideline is as follows:
If the score for any one hip is greater than 8 or if the score for any one of the 9 features listed on the score sheet is greater than 3 the dog should not be bred from. Once sufficient numbers of the breed have been assessed (100) an average for the breed
can be established and then the selection criteria should be that no one hip should have a score of greater than ½ the average score.
As the breed average score drops so will the score that is acceptable for breeding.

Such a control programme can be taken a step further by recording the hip status of offspring so that it can be determined which sires are tending to reduce the hip scores of their progeny.

 

THE SCORING SYSTEM

HIP SCORE
Hip                                                          Right              Left

  • Norberg Angle                      _______________________
  • Subluxation                           _______________________
  • Cranial acetabular edge       _______________________
  • Dorsal acetabular edge        _______________________
  • Cranial eff. acet. rim             _______________________
  • Acetabular fossa                  _______________________
  • Caudal acetabular edge       _______________________
  • Fem neck exostosis             _______________________
  • Fem head recon touring       _______________________
  • Total                                      _______________________
  • Score ______ 

 

The 9 items listed on the scoring sheet are all details of the anatomy of the hip joint that can be seen on an x-ray film. Of these features 8 are scored out of 6 with 0 being normal.
One of these, the Caudal Acetabular Edge, is scored out of 5.
Therefore the worst possible score for each hip is 53 with the worst combined score being 106. 

 

THE GRADING SYSTEM

There is not a direct relationship between scoring and grading which causes considerable confusion.
The grading is done on the worst hip only. Because of differences in the assessment methods it is possible, though uncommon, for  a dog with a relatively low score to have a relatively high grade.
Generally speaking it is considered acceptable to breed from dogs with grades 0, 1, 2, and 3 and not from grades 4, 5, and 6.
It is probable that the grading system will stop being used sometime in the near future.

 

HIP DYSPLASIA

The hip joint is a ball and socket joint with the ball (femoral head) being on the proximal end of the thigh bone (femur) and the socket (acetabulum) being on the pelvis. If the hip joint is normal the ball is a neat fit in the socket.
Generally all new born puppies have normal hip joints but in those that have HD an abnormality develops during growth.
The problem appears to be in the growing of the socket. For the socket to grow bigger as the dog grows requires quite a complex process because it is difficult to grow a hole. With the acetabulum this is achieved by the three bones that make up one side of
the pelvis (ilium, ischium and pubis) joining at the acetabulum thus forming a complex pattern of growth zones.
If the acetabulum is to develop correctly the growth rate at these different zones has to be precisely matched. If it is not, the acetabulum will become distorted so that the ball is no longer an accurate fit and this is hip dysplasia.
Some recent research suggests that dogs with HD have problems with other bone growth zones but because these are mainly involving single bones they do not cause problems. 

Hip dysplasia in itself does not commonly cause lameness.
It only does so if it is of such a degree that the hip dislocates and this is uncommon.
So many dogs, particularly younger dogs, with hip dysplasia show no signs of lameness.
This combined with the fact that it is a developmental abnormality is the reason why we have to resort to assessing dogs for hip dysplasia from an X-ray taken when the dog is at least 12 months of age.

With dogs that have HD the ball is not a neat fit in the socket so the joint is subject to excessive wear and tear. This excessive wear and tear results in the development of degenerative joint disease (arthritis). It is the arthritis that causes the lameness. Other factors can impact of the degree of wear and tear the joint is subjected to.
The two main ones are the weight of the dog and the amount and type of exercise the dog takes.
Obviously the heavier the dog the more stress is put on the hip joint so large heavy dogs are more likely to become lame because of hip dysplasia than small light ones. Dogs that get a lot of exercise at fast gaits such as galloping behind a car or bicycle and dogs that do a lot of jumping or turning and stopping such as when fetching balls or sticks stress the hip joints and are therefore more likely to become lame. A normal hip joint can sustain these sorts of stresses without developing arthritis.
So the age at which a dog with HD shows signs of lameness and the severity of the lameness is influenced by an inherited component.
That is the degree of developmental abnormality of the joint. Then there is the environmental influence which is the degree of stress the joint is subjected to.

 

ELBOW DYSPLASIA

Elbow dysplasia is a disease with a high inherited component, which primarily affects intermediate and large breed dogs.
A high incidence of occurrence has been noted in some terrier breeds.
Typically, both elbows are affected. However, unilateral elbow dysplasia is not uncommon.

DEVELOPMENT

The elbow joint is composed of three bones (radius, ulna, and humerus) which must all grow together and fit perfectly. The radius and ulna are paired bones with the radius being the main weight bearing bone.
The normal elbow joint is characterized by a smooth transition from the ulnar articular surface to the radial surface. In a dysplastic elbow the edge of the ulnar surface lies above the level of the adjoining radius, creating a step between the radius and ulna and causing incongruity of the joint.

The height of the step may vary from barely noticeable to 4 mm or more. When this occurs the weight bearing force on the ulna is increased, resulting in excessive pressure on the medial coronoid process. This leads to fragmentation of the coronoid process. This usually occurs between 5 and 7 months of age.
A superficial to deeply grooved "kissing lesion" is often present on the humeral articular surface opposite the fragment. A cartilage flap or OCD (osteochondritis dissecans) lesion may also develop.
Secondary arthritis becomes evident at 6-7 months.
Compensatory adjustments during growth may occur in some dogs, tending to minimize unequal growth rates between the three bones and moving the ulna distally to better conform to the radius. However, excessive force is then placed on the anconeal process at the top of the ulnar articular surface. This force will cause a failure of ossification, leading to an ununited anconeal process. (UAP)

CLINICAL SIGNS

Affected dogs are frequently lame or have an abnormal gait. The gait is often characterized by excessive paddling or flipping of the front feet.

The animal may either hold the elbows out or tucked in and often stands with the feet rotated outward.
Many sit or lie down much of the time, or play for shorter periods of time than other dogs of comparable age.
They are often described as quiet or even lazy. Frequently, they are stiff when rising and tire easily.
Exercise typically makes the lameness worse. In dogs with bilateral elbow dysplasia, the lameness may seem intermittent or shift from one front leg to the other.
When both front legs hurt, dogs do not limp constantly. Rather, they shift weight off their elbows by altering their gait and stance. These dogs will only "limp" when one elbow is more painful than the other.
On examination, manipulation of the elbow is often resisted. Swelling and crepitus (grating) may be palpated. The swelling may be worse after exercise.
In some cases, the joint will be thickened. Muscle atrophy may also be present.

DIAGNOSIS

The routine monitoring for the presence of elbow dysplasia is carried out from a lateral x-ray of the flexed elbow joint taken when the dog is over 12 months of age. Correct radiograph technique is critical for making the diagnosis.
The grade is derived by measuring the amount of new bone that has developed as a result of arthritis. Unlike the grading systems for hip dysplasia the system for elbow dysplasia is used internationally.           

ADVICE

It is generally considered that dogs with grade 3 elbow dysplasia should not be used for breeding.  And that dogs with grade 2 should be considered a serious risk.

 

These are Rodorbal Sweet As Candy's xrays. She has perfect scores of 0:0 elbows and 0/0 hips

 

       

 

 Click here to view Candy's hip and elbow report under the AVA scheme: Candy's hip and elbow report 

Click here to view Gilly's hip and elbow report under the new CHEDS scheme: Gilly's hip and elbow report

 

 

 

 

 

Contact Details

Linda Malseed
Macarthur, VIC, Australia
Phone : Ph: 03 5576 1204 / 0427 836 427
Email : [email protected]