Practical actions to reduce the Lafora risk in MWHDs by the breed club
Lafora disease can occur in any dog breed due to the type of identified dodecamer repeat mutation associated with the disease . However in the Basset Hound, Beagle and Miniature Wirehaired Dachshund the same dodecamer repeat has been identified as causative in all three breeds [6, 8].
The problem of Lafora in MWHDs was recognized by the UK breed club and could be addressed because there is a series of canine organizations concerned with safeguarding and protecting the health and welfare of dogs. The development of a DNA test was started in collaboration with the researchers and since the Lafora disease DNA test was developed, the UK Kennel Club has maintained a publicly available database of the Lafora test results from dogs that participated in the UK Kennel Club DNA screening scheme .
Each quarter, the UK Kennel Club publishes details of new litters that have been bred so the Breed Council has been able to ascertain the DNA test status of the parents of each litter. That has been a key input to the Breed Council’s quarterly communication updates to breeders and owners on the success or otherwise of the screening program. Informing people about the number of puppies likely to be affected was a powerful message to increase DNA screening in MWHDs and increase the number of safe litters.
As expected, some MWHD breeders have chosen not to participate because of the decision to publish the results. However, it was considered important to be open and transparent about the extent of the problem in the breed. Similar way as hip, elbow and eye examination results are publicly available . In addition, communication of the need for screening was directed at owners and potential owners, as well as at breeders. This helped to create “demand side” pressure for Lafora-screened litters. Publishing the data on the proportion of unaffected and “at risk” litters (carrier x carrier, carrier x not tested, clear x not tested, not tested x not tested, homozygous x not tested) every quarter from the Breed Records Supplement provided further evidence of progress and is a good way to recognize what is being achieved and to support participating breeders.
An important aspect of avoiding or anticipating unintended consequences that might arise from implementing a screening program was to understand the systemic impact of the decision. With the Lafora DNA test, some breeders denied that there was a problem in MWHDs, despite the evidence from test results. Another response was to challenge the validity and reliability of the test. However, DNA testing of 733 MWHDs provides evidence-based data showing reliably the genotype frequencies in the population. Interestingly, a number of MWHD pet owners started campaigning for wider adoption of the test by breeders, with their experience of what it was like living with a Lafora disease affected dog.
This particular study of 733 MWHDs provides evidence to evaluate the genotype and allele frequency of the Lafora disease-causing mutation in the MWHD population, especially in the UK population with 548 tested dogs. The high number of tested dogs gives reliable information about the genotype frequencies among the MWHD population included in the study. However, the data represents allele and genotype frequencies over six years of testing and may not be representative of a current situation among MWHDs and as it is a random set of dogs from the whole MWHD population there might be a biased towards clear dogs if owners suspected their dogs being carriers or homozygous dogs and did not want to participate. On the other hand, the data does indicate that the carrier frequency is high and it is unlike that there would have been a dramatic drop among the current population or in a bigger testing population. In addition, the dataset represents mostly dogs of UK origin and genotype and allele frequencies cannot be generalized to the MWHD population worldwide. Genotype frequencies cannot be estimated in countries where testing numbers are low and do not provide statistical confidence. In addition, it is possible that breeders who suspect that they have carrier dogs or dogs at risk of Lafora disease are more likely to screen their dogs. Although the genotype and allele frequencies are the similar across Europe and North-America more samples evenly across different countries should be included to confirm this. In addition, more females were included in DNA testing as proportionally fewer males with desired morphological and genetic features are used for dog breeding. However, no significant difference between gender and genotype was observed in this data set.
In 2014, the UK Kennel Club approved the Lafora DNA test as a “required” test for breeders who were members of its Assured Breeder Scheme . Test results are added to the dog’s registration details, triggering publication of results in the next Breed Records Supplement, any new registration certificate, on certificates of any future progeny, and on the Kennel Club Health Test Results website. The Breed Council was able to use this approval to reinforce further the use of the screening program by Breed Club members who are expected to comply with its Code of Ethics .
DNA testing affects the breeding programs
Using the DNA test, Lafora disease in MWHD could be avoided by testing all dogs used for breeding and mating of carriers only with clear dogs. One advice for breeding would be to breed quality carriers to clear-testing dogs and replace quality carrier parents with quality clear-tested offspring for breeding. This would ensure the eradication of Lafora disease in purebred MWDH. Carriers should be kept as part of the breeding population as other recessive alleles may become more frequent and the genetic diversity of the breed might be compromised if the carrier dogs are removed from the breeding pool too fast. This is particularly important in MWHDs that have a Lafora disease carrier frequency of 31.9% among all the tested dogs and 35.2% in the UK population. Also, Lafora disease is not only genetic disorder in MWHD, other inherited diseases include, intervertebral disc disease (IVDD), ocular disorders, kidney disease and osteogenesis imperfecta [33,34,35,36,37]. The prevalence of IVDD in MWHDs in 17.7%  which is significantly higher than the frequency of 7.1% of homozygous NHLRC1 mutation associated with Lafora disease presented here. However, there has not been a genetic test available for IVDD until recently  which is likely to reduce the IVDD prevalence in MWHDs. It is possible that IVDD prevention has higher priority in breeders’ minds than prevention of Lafora disease but as genetic testing has become routinely used tool in dog breeding both test are likely to be used in MWHD breeding to prevent both diseases. The estimated effective population size of MWHDs in UK is 110, which could be considered to be a relatively safe level in order to maintain a viable population  and fortunately a number of dogs have been imported with non-UK bloodlines, so there is a wider choice of dogs to use for breeding.
The Wire Haired Dachshund Club (WHDC) decreed that a condition of using the subsidized screening program was that Lafora-affected dogs be excluded from future breeding programs to reduce the number of carriers in the population and because of possible risk to the individual dog as it was not known if breeding of a genetically affected female dog may negatively affect the disease course.
The MWHD population in the UK provides an interesting test population where the genetic test is used to screen the dogs used for breeding. However, even with the genetic test, there has only been a slight decrease in the frequency homozygous and carrier dogs. This indicates that even with the genetic testing the Lafora disease-causing mutation remains at a high frequency in the population. A limitation of this study is that only genetically tested dogs were included in this study and dogs clear based on parental genotypes were not, which might have had an effect to the observer decrease in the genotype frequencies. On the other hand, it is better for breed-wide health as a marked decrease in the genotype would suggest reduced breed genetic diversity. Over several more years of DNA testing, with the same slowly decreasing trend of frequency of carrier and homozygous dogs, the Lafora disease-causing mutation might be eradicated from the MWHD population. We also observed a decline in the number of dogs tested annually possibly due to availability of hereditary clear dogs for breeding and the owners do not need to test their dogs as the genotypes can be estimated based on the parental genotypes. In addition, the number of safe litters has also increase during the years the Lafora test has been available indicating that the test if used as a tool for breeding and breeders use either the test or the hereditary clear dogs for breeding to increase the number of safe litters.
The international dimension
MWHDs are owned and bred worldwide and the WHDC recognized that the Lafora problem was unlikely to be limited to UK-owned dogs. After development of the DNA test, breed clubs outside UK were encouraged to recommend to their members to test dogs. Consequently, screening is now being carried out by many breeders across the world, notably in the USA, Canada and Australia.
That MWHDs are owned and bred internationally also provides opportunities for reducing the risk of Lafora disease. The mutation was largely identified in UK-bred dogs, and most dogs outside UK were found to be free of the mutation. Importing these dogs and breeding them with UK dogs would enable breeders to reduce the risk of Lafora disease. Conversely, overseas breeders that previously or are currently importing from the UK needed to be aware of the risks they were facing if they are using or have used untested dogs in their breeding programs.
Other size and coat varieties of Dachshunds do not have Lafora disease-causing mutation
Interestingly the MWHD is the only Dachshund variety in which Lafora disease is known to occur, although there are 8 other varieties under the Fédération Cynologique Internationale (FCI) breed standards based on size and coat type. In some countries the cross-breeding of different coats and sizes is permitted. This practice also happened in the UK until the mid-1970s when it was decided that puppies from such litters would no longer be registered. Outside the UK, this means that it would be feasible for the Lafora disease-causing mutation to be introduced into one of the other varieties of Dachshund where it could become widespread in the population if no screening takes place. In the UK, because of the pre-1970s practice of cross-variety breeding, smooth-coated puppies are occasionally born in litters from two wire-coated parents. This is known as a “recessive coat”; the gene for the smooth coat being recessive to the gene for the wire coat. In 2016, the UK KC decided to amend the registration regulations, allowing the registration of Dachshunds born with a recessive coat type. The Dachshund Breed Council expressed concern that this could lead to Lafora disease entering the gene pool of other varieties. After careful consideration, the Kennel Club Board approved a recommendation from their Dog Health Group that the progeny of any Dachshund from two Miniature Wirehaired Dachshund parents, registered as a different coat type to their parents, must have a coat-type DNA test as a condition of registration, and will be endorsed by the Kennel Club (progeny not eligible for registration). The endorsement will be removed only should a clear Lafora test result be produced or if both parents are either tested as clear, or shown to be clear based on their pedigree.