Pre-Breeding Testing

by Linda Aronson DVM

Although the incidence is very low in this country - albeit more common in rural areas and the south - and it is a disease with no breed preferences, it is important to ensure that sire and dam are both free of brucellosis. This is a bacterial disease that results in abortion and infertility in females and ultimately testicular atrophy and sterility in dogs. Other parts of the dog are very rarely affected, and unless the dog is tested the disease won't be discovered until it has wrought devastating damage to a breeding program. To prevent this all bitches should be tested before they come into estrus (heat) if it is planned to breed them. Dogs should be tested at least annually or before breeding if they are used infrequently. New dogs should be tested on purchase and again a month later to prevent introducing the disease into a kennel. Be sure to allow adequate time for testing. Frequent false positives in the initially used test, may require a second or third type of test be done to ensure the dog doesn't have the disease. There is no vaccine for brucellosis and no proven cure. If a dog has tested positive on all three tests it should be removed from the kennel and spayed or neutered. There is some evidence that prolonged use of the antibiotics minocycline or doxycycline may clear the infection from a dog, but this is an expensive and lengthy proposition and nobody would advocate re-introducing such a dog into a sensible breeding program, no matter what its virtues.

Canine hip dysplasia (HD) has been reported to have an incidence of between 9 and 10% in beardies. How accurate that figure is we do not know. Certainly not all beardies are being tested and often times owners will choose not to submit X-rays for evaluation if their vets, or they themselves, believe that the dog will be deemed dysplastic by the veterinary radiologists who evaluate hips for the various registries. HD is the result of a poor match between the head of the femur (thigh bone) and the acetabulum (hip socket). This mismatch leads to deformity of the femoral head and acetabulum as well as damage to the articular cartilage, resulting in micro fractures and degenerative joint disease (DJD). The degree of laxity – looseness – of the joint determines the severity of the disease and the amount of DJD the joint ultimately sustains. HD is a polygenic disease. There is no evidence that environmental factors such as diet, weight, and amount and type of exercise can cause HD, although they can certainly exacerbate it in predisposed dogs.

Particularly in cases where the dog is mildly dysplastic there may be no clinical signs, particularly in young dogs of breeding age. Severely affected dogs are often reluctant to move – especially up stairs or jumping - and less active than normal. Lameness may be either intermittent or constant, and they may bunny hop, sway or be base narrow behind. As DJD worsens thigh muscles atrophy and increasing debility and arthritis become more prevalent.

The most common method for hip evaluation involves taking radiographs of the hips with the dog lying on its back with the hind legs parallel and extended. The largest registry performing this kind of evaluation is the Orthopedic Foundation for Animals (OFA www.offa.org). OFA has been a closed registry, in other words only dogs deemed "normal" were listed. As of July 2000 owners will have the option of deciding before they submit the X-rays whether to make the findings "open" in which case even if the dog is deemed borderline or dysplastic, the results will be reported in the registry. Because HD is a developmental disease, all dogs are born with apparently normal hips. As the dog ages however, signs of dysplasia will begin to appear. While OFA reports that hip evaluation is approximately 90% accurate at 4 or 5 months old when compared to follow up radiographs at 24 months, the registry will not assign a permanent OFA number to dogs less than 24 months old. When OFA receives the X-ray it is assigned randomly to 3 board-certified veterinary radiologists. The rating is based on a consensus of their opinions. If they disagree significantly then further veterinarians may be asked for an opinion – this rarely happens. Hips are classified as "normal" for which there are three categories – excellent, good or fair. This information together with the age at which the dog was evaluated, its sex, breed and whether or not it was permanently identified (tattoo, chip or DNA) appears in his OFA number. Dogs may also be deemed dysplastic in three categories – mild, moderate and severe. If the veterinarians are in doubt the dog will be termed borderline, and reassessment in 6 to 8 months is recommended. OFA advises that because hormonal effects may cause some bitches to show subluxation they should not be radiographed within 4 weeks of the beginning or end of their heat cycle, or within 4 weeks of weaning puppies. Preliminary OFA evaluation can be performed for dogs between 4 and 24 months of age. A single board certified veterinary radiologist evaluates the X-ray. Further X-rays must be submitted at 24 months or older for permanent registration. OFA stresses that it is not only important to breed dogs with "normal" hips, but they should have an ancestry of normal hips and come from litters with low or zero incidence of hip dysplasia.

In 1983, PennHIP was introduced to address a number of shortcomings in the traditional method of hip evaluation. The latter may give a false impression of joint tightness although it is good at detecting existing DJD. For this reason the results are not deemed reliable until dogs are 24 months or older. For PennHIP evaluation a second "distraction" X-ray is taken of each dogs hips. This enables the evaluator to measure the degree of laxity of the femoral head in the acetabulum (distraction index - DI). A third compression view is also recommended. The advantage of PennHIP is that it enables accurate hip evaluation by 6 months of age (or even 4 months although results are slightly less good.) It also seems that joint laxity is more clearly heritable than DJD, which can be affected by environment, and may be a better predictor of hip health, particularly in dogs where extensive information about other family members is lacking. However, there are disadvantages. First the three radiographic views, which have to be taken under heavy sedation or general anesthesia, add considerably to the evaluation cost. More importantly, it seems that the acceptable degree of laxity is somewhat dependent upon breed. More heavily muscled breeds being able to sustain greater laxity. Too few beardies have been evaluated by PennHIP to make clear recommendations at this time, although dogs with DIs of < 0.3 in each hip are preferred and dogs with DIs > 0.7 are at high risk of developing dysplasia.

Another orthopedic condition that has been reported in beardies is elbow dysplasia. Actually, this is a blanket term covering at least three different developmental aberrations or a combination thereof. By far the most common is fragmented coronoid process (FCP) with or without osteochondritis dissecans (OCD) or condyle erosion (>90%) while < 10% involve ununited anconeal process (UAP). (The anconeal process is a bump near the upper end of the ulna – the thinner of the two bones in the forearm. It fits into a notch on the humerus – upper arm bone. There are two coronoid processes slightly lower down the ulna into which the head of the radius – the thicker of the forearm bones – nests. The medial one is more likely to be affected. The condyle is a catchall name for the big knob at the lower end of the humerus. OCD describes a condition where flaps of thickened cartilage separate partially or completely from the layer inside the joint, causing irritation and inflammation.) We do not know how prevalent this problem is in beardies, we do know however, that while elbow dysplasia is more common than HD, it is less likely to be diagnosed. At this time relatively few beardie breeders have been including elbow X-rays as part of their pre-breeding testing and it is probably similarly under diagnosed in the breed. The elbow is the most complicated joint in the body and as such liable to more problems. As with HD, dogs may not appear particularly painful while young, or onset can be sufficiently slow as to be deemed a normal part of aging. Dogs rarely complain about chronic pain, which is why owners are often unaware that they are suffering from either hip or elbow dysplasia. Pain is caused by fluid build up in the joint and the presence of bone fragments. Eventually weight bearing may be compromised. Healthy dogs bear 60% of their weight on their front legs, with elbow dysplasia this may drop to 40 to 50%. The elbow may appear fused in extreme cases. Screening X-rays for elbow dysplasia require that the joint be radiographed in extreme flexion. OFA also has a registry for elbows. Animals must be 24 months or older. As with HD, there will be the option to choose to be part of the open registry after July. While there is only one category for normal elbows at this time, abnormal elbows may be reported as Grade I- minimal bone change on the anconeal process; Grade II – additional subchondral bone changes and or osteophytes (remodeling of bone in the joint); Grade III – well developed DJD.

The eyes also do not seem to be getting the attention they probably deserve. There seem to be an increasing number of beardies going blind. Like the bones, the eyes tend to change most dramatically during early to middle years when a dog is being used for reproduction. For this reason, the Canine Eye Registration Foundation (CERF), located at Purdue University’s School of Veterinary Medicine, recommends annual testing of dogs. As with OFA data, your dog’s CERF status will appear on AKC registration forms, provided your dog has been permanently identified (tattoo, chip or DNA). At this time CERF is a closed registry. Only dogs deemed free of heritable eye disease can be registered. However, the examining veterinarian, who must be a board-certified diplomate of the American College of Veterinary Ophthalmologists (ACVO) submits data on all dogs which fail to test clear. This data is used for research purposes. From 1991 to 1999 a mere 931 beardies were examined. While an encouraging 761 (81.74%) tested clear a variety of different types of cataracts (lesions of the lens) were reported. Another common problem seen was persistent pupillary membranes (PPM - remnants of embryonic blood vessels). This was found in more than 1 in 6 of the beardie eyes examined at the CERF clinic offered when MBCC staged the 1998 BCCA specialty. Retinal atrophy and globe (eyeball) problems were also reported. It should also be born in mind that not all cases of PPM would be reported. Many ophthalmologists do not examine the eye before dilating the pupil. Because PPM are present on the iris, which retracts when the pupil dilates, they will not be seen (or not as clearly) on post-dilation examination. While PPM and cataracts have been deemed heritable in many breeds, PPM is not a disqualifying fault at this time for beardies. Given the reported incidence CERF may change their opinion on that in the near future. In the meantime however, beardies with PPM receive CERF registration. Whether or not an ophthalmologist decides certain types of cataract are heritable or not is also somewhat in the hands of the individual currently.

Probably autoimmune diseases – diseases in which the immune system fails to recognize self and forms antibodies against a part of its own body - are the most feared in the beardie community, but at this time we do not have a predictive test for them. The most common autoimmune disease in beardies and other dog breeds is hypothyroidism – or immune mediated thyroiditis. This is not particularly surprising, dogs that couldn’t reproduce due to insufficient thyroid hormones have traditionally been bred after supplementation, and we know this happened with beardies. What wasn’t known at the time, however, was that hypothyroidism might also predispose an animal to develop other autoimmune diseases. Recently, we have also learned that hypothyroidism is often manifested in its earliest stages in behavioural problems – aggression, hyperactivity, fearfulness and obsessive behaviours. All of these have been seen in beardies. Testing breeding stock for hypothyroidism is clearly prudent. However, the most common thyroid test (total T4) done in veterinary medicine is rarely positive until 2/3rds of thyroid function has been lost. It is recommended that the whole thyroid function be examined through a thyroid profile. Many labs offer a 6-analyte-thyroid profile (total and free thyroxine (T4) and triiodothyronine (T3) as well as autoantibodies to T3 and T4.) For breeding stock it is optimal that the first four of these be in the upper 50% of lab normal values, and for animals under 18 months the upper 75%. In dogs over 8, thyroid levels may drop below the midpoint as metabolism begins to slow. OFA also offers a thyroid panel measuring free T4 by equilibrium dialysis, canine TSH levels and thyroglobulin autoantibodies. It should be noted that much controversy exists as to which testing method is preferable. Different labs use different assays to measure the various analytes and these are of variable accuracy. Dogs should be tested once they have passed puberty. Bitches should be tested during anestrus, the period 12 weeks after the end of the previous heat to 12 weeks before the onset of the next heat. It is recommended that both dogs and bitches be retested annually. This allows comparisons for early recognition of developing thyroid dysfunction. The earlier treatment is initiated the fewer clinical problems associated with hypothyroidism will be manifest. If a dog tests low it should not necessarily be removed from the breeding program. Illness may drop circulating thyroid levels (sick euthyroid) as will various stressors. However, it would be unwise to breed the dog until a follow up panel showed that its hormonal levels had returned to normal. At the same time, if a dog shows clinical signs of hypothyroidism but the serum (blood) levels are normal it may have a deficiency of the hormones at the tissue level. If the dog responds to a 6 to 8 week trial of thyroxine replacement this is very likely the case. Selenium deficiencies may manifest in this fashion.

While we are still waiting for a genetic test for Addison’s disease, an annual complete blood count (CBC) and biochemical profile may prove very helpful for early detection. In Addison’s disease the body’s ability to balance sodium and potassium levels is usually the most seriously compromised function, and as a result nerve and muscle activity is impaired. The biochemical profile gives baseline data on electrolyte levels (including sodium and potassium) so any changes from one year to the next are clearly seen. Important information on liver and kidney function is also to be found. The CBC, as its name implies, gives information on numbers of the various types of blood cells, allowing anemia, thrombocytopenia and leukemia to be recognized. Signs of infection and stress can be detected, too. Any slightly "abnormal" normals for a particular dog will be seen from year to year. (For example many beardies have a normal level of eosinophils – a kind of white blood cell – that is slightly higher than lab normal.) Early detection and treatment results in a better prognosis for almost every condition.

Another blood test that is advisable is for von Willebrand’s factor (vWF). Von Willebrand’s Disease (vWD) is a bleeding disorder somewhat akin to hemophilia. VWF circulates in the blood and helps platelets to stick together to form plugs when there is a breach of the blood vessel wall. We know that beardies have a mild form of the disease. As for many diseases we do not know the prevalence in the breed. Often the disease is found during surgery, and some beardies have bled to death during spay/neuter operations. For many breeds VetGen has a DNA test. This is probably effective for beardies too, but as yet insufficient beardies with vWD have sent samples to the lab to prove this. For now, a blood test is necessary to measure vWF levels. Like PennHIP there is a gray area between known carrier and known clear. We can only suggest that dogs in this range be bred to dogs that have significantly higher vWF levels. The level of vWF in the offspring tends to average those of the parents. A single popular sire with low vWF levels could be disastrous, as it was for Dobermans, where 90% of dogs were carriers for the disease before the problem was recognized.

OFA operates a couple of other registries that may be relevant for beardies. It has been reported that beardies are at risk for a cardiac condition called subaortic stenosis (SAS). SAS is a narrowing of the aorta just below its exit from the heart. This means that the heart has to work harder to pump blood out to the body. In clinical cases a systolic ejection murmur should be detectable. Echocardiographic (ultrasound of the heart) screening of the heart may be advisable, especially in beardies with relatives that have been diagnosed with SAS.

Patellar luxation – displacement of the kneecap – is most common in toy and small dogs. We have little to indicate that this is a significant problem in beardies.

At this time I would recommend that all dogs be tested for brucellosis a few weeks before breeding, or annually/biannually for stud dogs that are used fairly frequently. Hips and elbows should be X-rayed at 2 years of age, or earlier if the dog is to be used before it is 24 months old. CERF and thyroid preferably should be repeated annually post puberty (for bitches these tests, as well as X-rays and vWF test, should be done during anestrus.) I would also strongly recommend annual CBC and biochemistry profile and a post-pubertal vWF. In the future, as new and better tests become available these recommendations will doubtless change. The canine genome project approaches completion, and it is not inconceivable that a DNA profile of our dogs will be all that’s needed to assess a dog or bitch’s status as regards these and other inherited diseases.

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