The Rhodesian Ridgeback Club of the United States Rhodesian Ridgeback Club of the United States

HEALTH & GENETICS RESOURCES

GENETIC TESTING

Hip Screening

Hip dysplasia is a devastating genetic disease that can eventually produce painful and crippling arthritis. The genes that cause hip dysplasia are inherited from a puppy's parents, though the sire and dam themselves may not necessarily have the disease. Hip dysplasia is polygenetic - a combination of genes from each of the parents produces a dysplastic hip. Hip dysplasia affects many breeds to varying degrees. The size of the breed has little to do with the disease. The biggest contributing factor is the abnormally developed hip joint, which was inherited from the sire and dam.

The hip is a ball-and-socket joint. In a normal hip, the socket surrounds the ball securely. When the socket is shallow, the ball is not secure and will move abnormally. Because of this abnormal stress placed on the hip, the cartilage of the joint becomes damaged. As the cartilage erodes, arthritic changes appear in the joint. Ability to move the joint will eventually be reduced. Click here to see the anatomy of the canine hip and how dysplasia manifests in the joint.

X-rays are the only way to evaluate hips for dysplasia. In young dogs, before there are arthritic changes, the ball and socket of the joint can be seen and the depth of the socket evaluated. A very shallow socket will eventually cause arthritic changes. While X-rays can tell you if a dog has a dysplastic hip, they cannot tell you the degree the dog will be affected. Amazingly, there are dogs with severely affected joints who seem to move well, and other dogs who appear to be only mildly dysplastic who are crippled. There are many things that can influence the appearance of clinical signs, such as calorie intake, level of exercise and even the weather. The important point is that just because a dog moves his hips well does not mean he is not dysplastic. There will be some degree of arthritis in the hip joints as the dog grows older.

The following are the most common hip evaluations done in the United States:

Elbow Screening

Elbow dysplasia is a general term used to identify inherited arthritic disease in the elbow of dogs. The genes that cause elbow dysplasia are inherited from a puppy's parents, though the sire and dam themselves may not necessarily have the disease. Elbow dysplasia is polygenetic - a combination of genes is required from each of the parents to produce a dysplastic elbow.

There are basically three causes of elbow dysplasia, and they can occur alone or in conjunction with each another. These are:

  1. Pathology involving the medial coronoid of the ulna (FCP)
  2. Osteochondritis of the medial humeral condyle in the elbow joint (OCD)
  3. Ununited anconeal process (UAP)

While X-rays will tell you if an elbow joint is abnormal, they cannot tell you when or how severely the dog will become lame. Much has to do with weight and speed of weight gain, as well as the amount of exercise the dog gets. Lameness can be subtle for a very long time. There might be very subtle changes in gait, particularly an excessive inward deviation of the paw so that the weight is carried on the outside of the elbow rather than on the inside of the joint, where the dysplasia occurs. Range of motion in the elbow will also decrease.

The following is the only elbow evaluation available in the United States that we are aware of:

Eye Screening - CERF (Canine Eye Registry Foundation)

Diseases of the eye can be particularly devastating because many can lead to blindness. There are many kinds of eye disease, and all should be considered heritable unless you are told differently by a veterinary ophthalmologist. Eye disease is hereditary.

Rhodesian Ridgebacks generally have very healthy eyes. One condition we are aware of that occurs with some frequency is a small juvenile cataract. Some argue that since this cataract is small and does not interfere with vision it is not a threat to the breed, but nothing could be further from the truth. Breeding dogs with even small cataracts to other dogs with small cataracts -- or even with a strong family history of these cataracts -- will produce more cataracts. In other breeds this practice has eventually led to the production of large, blinding cataracts in subsequent generations.

All breeding Ridgeback stock should receive a CERF (Canine Eye Registry Foundation) examination annually until age 9. In this examination, which involves dilating the dog's eyes, every part of the eye is evaluated. This exam can only be done by a veterinary ophthalmologist.

Thyroid

Hypothyroidism caused by lymphocytic thyroiditis is the most common disease found in Rhodesian Ridgebacks and is very heritable. This is an autoimmune disease --- that is to say, the dog's body does not recognize the thyroid gland as being part of "itself" and attacks it as if it were a foreign body. It can take a long time before the thyroid gland is destroyed to the point where the dog cannot produce thyroid hormone and actually becomes hypothyroid. Often dogs have already been bred before they show clinical signs.

In light of this, all Rhodesian Ridgeback breeding stock should have the following labs done annually between 1 to 6 years of age. It is recommended dogs have one final evaluation at 8 years of age.

  • Free T-4 by Dialysis
  • Thyroid Stimulating Hormone (TSH)
  • Thyroglobulin Autoantibody (TgAA)

The Free T-4 and TSH show the current status of the dog's thyroid hormone production. TgAA is the antibody that is produced when the thyroid gland is being attacked. If the TgAA is elevated, even if the other labs are normal, it is likely a dog will become hypothyroid later in life. Such dogs should be considered "affected" and should not be bred.

Hearing and Cardiac

While there is deafness in the Rhodesian Ridgeback, thankfully it is not a widespread problem. We encourage all breeders to obtain BAER (brain auditory evoked response) testing on their breeding stock to ensure this does not become a bigger problem in the future. We do know that Ridgeback deafness is not the same deafness found in Dalmatians—that is, it is not related to color. We know that it is inherited and it is autosomal recessive, meaning that a normally hearing sire and dam can produce deaf pups if they each carry a deafness gene. A pup must have two of these genes to be deaf. With none or only one deafness gene, the Ridgeback will hear normally. If a pup inherits a deafness gene from each parent (i.e., two genes total), he will be deaf by approximately 9 months of age. Because this deafness can occur late in the first year of life, BAER testing should not be done until 1 year of age.

A cardiac evaluation is an optional test that is recommended in lines where there have been concerns about heart disease. This evaluation can be done by a general veterinarian, a veterinary cardiologist or veterinary internal medicine specialist. The Ridgeback is evaluated for a murmur. If a murmur is present, more testing may be recommended to determine the cause. For OFA Cardiac certification, the dog must be at least 1 year of age.

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