AWARDS NOTE

AKC SURVEY

Pet Food Info

FIRST  SV  AKC CHAMPION

BOARD MEETING DATES

Our 1st Westminster Winner

MA Supported Entry 11/21/08

Tulsa Supported Entry 11/1/08

SVs on YouTube

Vaccine Study

Composite Picture

last  updated on:   07/14/08       

WebManager & Info
Gail Smyka
(click to email)
email with suggestions, info, corrections
thank you very much



 

Genetics

reprinted from SVCA Newsletter, Spring, 2003, with permission. Mr. Clayton is the chairperson of the SVCA Genetics Committee.

Some Genetic Defects Associated with the Swedish Vallhund
By David Clayton

The Swedish Vallhund is a healthy breed with few genetic disorders. Those disorders that are present generally occur at low frequencies. This is due in no small part to the diligence of the Swedish people, who are determined to keep the breed healthy and true to its heritage. While the breed is relatively free of genetic disorders, the following defects have been associated with the Swedish Vallhund: hip displasia, luxated patellas, cleft palate, retinal dysplasia, cryptorchidism, missing teeth and bad bites.

 Canine Hip Dysplasia

There is ample scientific evidence establishing that canine hip dysplasia is a polygenic (many genes involved) disorder which is environmentally influenced. The major registries that evaluate hip conformation in the US are OFA and PennHIP. These registries are "semi-open" and won't reveal information on affected dogs unless owner permission has been obtained. According to the most recent OFA data base (3/14/2002), 33 Swedish Vallhunds have passed OFA standards for hip conformation, (1 Excellent, 22 OFA Good, and 10 OFA Fair). No trends or percent dysplastic have been determined for the breed in the United States as fewer than 100 individuals have been evaluated. However, internationally, the breed is reported to have a low incidence of hip dysplasia.

The patella, or kneecap is located in the stifle joint in the 2 hind legs of dogs. In patellar luxation, the kneecap luxates, or pops out of place. Luxated patellas are a congenital (present at birth) condition. The actual luxation may not be present at birth, but the structural changes which lead to luxation are present. Some signs of a slipped kneecap are difficulty straightening the knee; pain in the stifle; and a limp. The diagnosis is confirmed by manipulating the stifle joint and pushing the kneecap in and out of position. Most researchers believe luxated patellas to be heritable, though the mode of inheritance is unknown. However, some researchers have suggested a recessive method of inheritance. Currently dogs affected with luxated patellas are uncommon in the Swedish Vallhund, though it may occur more frequently in certain lines. Dog with patellar luxation should not be used in a breeding program. In the US, OFA currently evaluates patellas to identify those dogs that are phenotypically normal prior to use in a breeding program and to gather data on the genetic disease of patellar luxation.

The palate (roof of the mouth) is a wall, partitioning the nasal and oral cavities.  This partition is made up of two parts: the hard palate and the soft palate.  The hard palate forms the front portion of this partition and is made up of two bony plates (one on each side) that are normally fused together at their midline juncture.  This fusion normally takes place during fetal development. The most common type of cleft palate results when the two bony palate plates fail to fuse. The cleft is present at birth and can usually be detected by examining the roof of the mouth. The only treatment for a cleft palate is to surgically close the opening.  In cases of severe clefts the affected pup is usually euthanised. Most cleft palates are assumed to be genetic unless other causative factors are found. The mode of inheritance of cleft palate is unknown. This disorder is very uncommon in the Swedish Vallhund.

The cause of retinal dysplasia in most breeds is genetic. Retinal dysplasia is a type of retinal malformation. Retinal dysplasia occurs when the 2 primitive layers of the retina do not form together properly. Mild dysplasia manifests as folds in the inner retinal layer. These are called "retinal folds". In "geographic" retinal dysplasia there are larger areas of defective retinal development. In the severe form of dysplasia, the 2 retinal layers do not come together at all and retinal detachment occurs. In the mild form, retinal folds rarely cause vision problems for the individual dog. They represent small blind spots. However, large areas of dysplasia (geographic dysplasia) may lead to large deficits in the visual field and dogs with retinal detachments are completely blind. Retinal dysplasia is not progressive. It is a congenital defect and animals are born with as severe a condition as they will ever get. Retinal dysplasia can be detected as early as 6-8 weeks on a CERF examination. The mode of inheritance for retinal dysplasia has not been determined in the Swedish Vallhund. Retinal dysplasia has been found in several lines in the US. Most cases of retinal dysplasia observed to date in the Swedish Vallhund have been minor and may not result in any loss or significant loss of vision. However, it is important to CERF puppies to determine which pups may be affected and to determine if more significant types of retinal dysplasia may occur within the breed. Individuals affected with retinal dysplasia may be useful in a breeding program, though it may be more appropriate to preferentially use non-affected relatives. Linebreeding within lines known to carry retinal dysplasia is not recommended.

Cryptorchidism is the term used when one or both testicles of a male dog or cat have not dropped down into the scrotal sac (retained testicle). If one or both testicles are missing by 2 months of age, he is considered cryptorchid. Most researchers believe cryptorchidism is inherited. A testicle is retained, it is 10 times more likely to become cancerous, therefore surgical removal of both testicles is highly recommended upon diagnosis. Approximately, 53% of sertoli cell tumors and 36% of seminomas (both are testicular cancers) are from cryptorchid dogs. Due to the inherited nature of the condition, neutering is recommended to prevent passing on the trait. The neutering procedure is often more difficult than a normal neuter because abdominal exploratory surgery is often performed in order to find testicle. Cryptorchidism is thought to be uncommon in the Swedish Vallhund.

Missing teeth have been observed in the Swedish Vallhunds in the US. Inherited missing teeth usually occur within the pre-molars adjacent to the canines on the top and lower jaws. The number of teeth missing ranges from one to many. Teeth that are not there cannot perform their function. A full complement of teeth is highly desirable and should be preferred. Missing teeth may lead to excess wear on the remaining teeth and a shifting of the surrounding teeth into the gap. The mode of inheritance of missing teeth is unknown. At this time the frequency of missing teeth I have observed in the Swedish Vallhund is low but not uncommon. This is an area that we will have to pay particular attention to in the future.

Bite problems are relatively uncommon in the Swedish Vallhund. Most dogs have scissors bites as called for in the standard. However, on occasion, level bites, overbites, under bites, and malocclusions occur. Minor level, over, or under bites normally cause few problems for the dog, though excessive wearing of the teeth may occur. Although rare, extreme under bites, and overbites (parrot mouths) have been observed and can interfere with the dog’s ability to eat properly. Dogs with any of these conditions are not recommended for breeding. These conditions are thought to be inherited, though the mode of inheritance is currently unknown.