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EUROPEAN AND AMERICAN STUDIES OF INTERVERTEBRAL DISC DISEASE

 

Several studies have been conducted in America and Europe over the years relating to intervertebral disc disease (IVDD) in the dachshund.  The results of those studies are presented below. Many thanks to Finnish DCA Member Silja Linko-Lindh for the information presented here and for her assistance in both translating and interpreting the results.

  In 1980, a project conducted by Havraneck & Balzaretti in Switzerland consisted of an x-ray study of 209 dachshunds between the ages of 12 and 18 months.  Of the dogs that showed calcifications, 79% got IVDD symptoms later, while dogs with clear x-rays lived without problems.  As a part of the study, some of the x-rayed dogs were bred to each other. The offspring were x-rayed at the age of 12 months, with the following results:  if both parents were free of calcifications, 30% of the offspring had calcifications; if one calcification-free parent was bred to one with calcifications, 56% of the offspring had calcifications; if both parents had calcifications, 83% of the offspring had calcifications.  This study gives strong evidence to support the theory that calcified discs tend to herniate and that calcifications are hereditary.  The connection between calcifications and paralysis seems undisputable if credence is given to this study.

 A project conducted by Ball et al in the U.S. in 1982 consisted of a pedigree-study of 536 dachshunds. There was an overall IVDD occurrence 19%.  Thirty-one of the dogs in the study were the offspring of the same afflicted stud: 61 % of them (19 dogs) had IVDD problems.

The Stigen project, conducted in Norway during the years spanning 1991-1996, consisted of x-ray studies of 327 dachshunds, ages 12-18 months.  Of them, 115 dachshunds returned for new x-rays five years later. Conclusions: dachshunds with calcifications at the age of 12 months have a four-time greater risk for problems than dogs without calcifications.  Calcifications can increase but they can also disappear.  Another conclusion of this study was that disc calcification is hereditary.
 

A short summary of the thesis written by the Danish veterinarian Vibeke Jensen (approved on September 28, 2000) to outline the results of his extensive study in this area has been provided below by Anu Lappalainen, and translated from the Finnish by Silja Linko-Lindh:

 The study was divided into 5 parts, and four of them are published or accepted for publishing in various veterinary journals.

 Part One

 Development of Intervertebral Disc Calcification in the Dachshund: A Prospective Longitudinal Radiographic Study [Journal of the American Animal Hospital Association, 7/2000]

 Dr. Jensen followed the development of calcifications in forty dogs from eleven litters by x-rays.  Four of the litters were wirehaired dachshunds, 4 litters were smooths, one litter was longhaired standards and 2 litters were longhaired miniatures (FCI breed standard). The dogs were x-rayed at the ages of  6, 9, 12, 18 and 24 months and some also at the age of three or four years.

Results:  The first calcifications were already evident at the age of 6 months but the highest number of calcifications appeared between the ages of 12 and 18 months. After 24 months new calcifications were few and appeared only in those dogs who had several calcifications.  Many of the calcifications were barely visible before the age of 24 months, but could be confirmed with certainty at that age.  Calcifications started to disappear at the age of 18 months, and that phenomenon accelerated after 24 months. The disappearance of the calcifications was more common in dogs with several calcifications.  At the age of 12 months 53% of the dogs had confirmed calcifications and 7% were suspected cases.  At the age of 24 months 80% of the dogs had calcifications (averaging approximately 3.2 calcifications per dog). Of the calcifications, 80% were in the thoracolumbar (mid-back) area.

Conclusions:  Dogs should be at least 2 years of age when x-rayed. Most calcifications can be seen at the age of 24-27 months.

 Part Two

 Occurence of Intervertebral Disc Calcification in the Dachshund [Journal of Veterinary Medicine, Series A, 47 (5): 283-296]

This was a study of the effects of mechanical phenomena (exercise, climbing stairs, hunting, running with bicycle) on the occurence of the calcifications. Forty-eight wirehaired standard dachshunds (FCI breed standard, not over 9-10 kilograms,) were elected to represent the Danish dachshunds, with offspring of imported dogs and frequently used sires being avoided.  Also avoided were females from heavily bred lines.  Dogs were 24-55 months old, clinically healthy and had not been treated for back problems.

Results:

77% of the dogs had calcifications, averaging 4.5 calcifications per dog. The connection between climbing stairs and calcifications can be considered statistically significant.  Moderate climbing decreases the number of calcifications. Running alongside a bicycle a couple of times a month increased the number of calcifications, but dogs with this kind of exercise were only 4 of the 48, so the result could also be a coincidence.  Conclusions: moderate unleashed exercise and moderate climbing of stairs have a positive effect of the health of the discs. The reason seems to be the better metabolism of the intervertebral discs. But climbing stairs is still a risk for dogs with clearly and strongly calcified discs.

 

Part Three

Inheritance of Intervertebral Disc Calcification in the Dachshund [Journal of Veterinary Medicine, Series A, 47 (6): 331-340]

Eight males, 16 females and 69 of their offspring (all wirehaired standards, FCI standard) were studied. Every litter in the sample was represented by at least three dogs. The offspring were between two and three years old. None of the offspring had had any symptoms of intervertebral disc disease but one of the mothers had the disease diagnosed.

 Results: 100% of the sires, 75% of the dames and 80% of the offspring had calcifications. If both parents had calcifications 91% of their offspring had calcifications. If only one parent had calcifications, 44% of the offspring had calcifications. The heredity rate, depending on the counting method for the occurence of the calcifications, is between 0.46 and 0.87. The rate is higher between dam-offspring than between sire-offspring. (That fact could be due to the effect of environmental factors associated with the dam, such as rough play with the pups, litter size, and nutrition.) Conclusion: calcification of the intervertebral discs is hereditary.  The phenomen can be controlled and significantly decreased by breeding choices.

 Part Four

Asymptomatic Radiographic Disappearence of Calcified Intervertebral Disc Material in the Dachshund [Veterinary Radiology and Ultrasound, 7/2000]

 The same 40 dogs used in the study outlined in Part One were followed with new x-rays at the age of 3-4 years.

Results: Nearly 10% of the calcifications had disappeared partly or totally. It is notable that the disappearance occurred only in those dogs who had more than 4 calcifications and more calcifications disappeared in litters where all of the dogs had calcifications. The calcifications that disappeared had been more calcified than others and had been obvious for a longer period.  This seems to indicate that calcifications disappear only from strongly degenerated discs. The mechanism of symptomless disappearance of calcifications is not known.

 Part Five

 Deformity of discs.

This study has not been published so the correct name for it is not known. The short result is that the deformity of discs seems to be hereditary but doesn't seem to have any connection with the calfications of the intervertebrals discs.

 Study #1 is credited to Jensen V & Arnbjerg J.

Study #3 is credited to Jensen V & Christensen K.

 
A line-based study in Denmark studied 126 dachshunds in 26 litters, with at least one afflicted dachshund in each litter.  Afflicted sires and grandsires were heavily represented, while dames and granddames were usually health.  (That fact may indicate that the breeders whose litters were studied knew their bitches’ lines better than they knew the lines of males they used.) The wirehaired standard sized dachshunds (80% of x-rayed dogs) had the most calcifications. The study concluded that the best time to x-ray is between the ages of one and two years. After that age the calcifications don't increase but they can disappear. The breeding committee of the Danish dachshund club recommended at the conclusion of the study that only dogs free of symptoms be used for breeding and that the health of the grandparents should be checked. If it is not possible to check the back history in the line behind the stud, then using males over 8 years of age was recommended, as most occurrences of IVDD will have occurred before that age.

 The science represented above supports what many breeders already believe:  while many factors contribute to disc disease, it is probable that the most significant of those factors is heredity.  

 If x-raying breeding stock for calcifications can indicate which animals are most likely to produce offspring who suffer from disc disease, and if that information can be used to slowly but surely lessen the occurrences of IVDD in dachshunds, then responsible breeders have a very effective tool to use in an attempt to greatly reduce the occurrence of the breed’s largest health problem.  Dachshund owners can also utilize x-rays to have an idea of whether or not a particular dog is predisposed to IVDD, and this could be a very valuable asset in determining whether or not a dog is suitable for agility training or for other activities that incorporate jumping.  It is probably quite important that the x-ray equipment be of high quality and that the dog is placed in the specified positions to facilitate reading of the x-rays.

 Thanks to Dr. Marilyn (Julie) Roane for rendering these superb drawings and for lending her veterinary expertise as a consultant in presenting the results of the studies. 

These drawings show the optimal positioning of the dachshund for taking x-rays to determine if disk calcifications are present.  Two x-rays should be taken of the dog, one with the front legs in the forward position and another with the front legs moved back, as pictured in drawings #1 and #2.

Drawing No.1

Drawing N0.2

This offers the veterinarian two views of the areas between the vertebrae; comparing the two x-rays is very helpful in making the determination as to whether or not calcifications are present. Sandbags are used to hold the legs in place and cushions are placed as pictured in order to maintain the proper alignment of the spine.

Drawing No.3 illustrates the correct separation of the rear legs with a cushion

Drawing No. 4 shows the correct angle of the x-rays as well as offering an anterior view of how the cushions should be placed.

Reprinted from the DCA Newsletter, December, 2001.