It’s in the DNA

DNA sequencing is the process of determining the precise order of nucleotides within a DNA Whole genome sequencing has made the complete DNA sequence of an organism available for analysis and study. The first organism to be sequenced in 1977 was a virus and the human genome project was launched in 1990, with the first draft of the full sequence being published in 2001 and the final draft in 2003. The dog genome was published in 2005 and <ahref=”https://research.nhgri.nih.gov/dog_genome/study_descriptions/publications-study.shtml#genomics_dog_breeds” target=”_blank”>several peer-reviewed publications detail research into the origins of the domestic dog, variations in physical characteristics and canine diseases.

Originally an expensive process, DNA testing and sequencing has become considerably cheaper and 19 laboratories across the globe support commercial provision of approximately 200 DNA tests, most commonly undertaken for disease prevalence and to determine breeds in crosses. However, not all DNA tests are the same. Knowing what breeds constitute a cross may provide a broad idea of temperament but the effects of epigenetics and other environmental factors, not to mention training, play a huge role in determining how a dog will behave. Even where susceptibility to disease and defects are concerned, DNA tests need to be treated with caution, as indeed do other tests such as screening for hip and elbow dysplasia which need to be seen in the context under which the results are reported as well as assessing the validity of the tests themselves. Inaccuracies in human genetic tests can be as high as 40% and with humans and dogs, the tests are often only partial, with companies failing to screen for all known disease-linked mutations. For example, a mutation in the ABCB1 gene occurs in many herding dogs including collies, Australian shepherds and Shetland sheepdogs that renders them susceptible to poisoning by commonly used veterinary medications such as flea and worm treatments., Although there is a genetic test available to screen for one type of this mutation, it appears that two other types are not screened for which may result in dogs being designated as clear when they are not.

An article in the prestigious journal Nature has raised serious concerns about the scientific basis behind DNA testing to predict the likelihood of disease occurrence as well as concerns regarding conflicts of interest. They state that most genetic tests for health are based on small studies where the accuracy and ability to predict health outcomes has not been validated. Owners are likely to come across the results via breeders and/or vets, neither of whom are unlikely to possess detailed knowledge about the limitations of such tests. This can not only lead to owners being misled, but to dogs undergoing invasive and unnecessary testing and even being euthanised on the basis of the results.

As with human DNA testing, researchers look for mutations on “candidate genes” that might lead to future genetically-linked health problems. However, just possessing a mutation is not guarantee that disease will develop: this has only been found to be the case in 2% of human candidate gene studies. In human genetics, collaboration between industry, academia, doctors and patients has resulted in a more detailed and nuanced assessment of the effect of candidate genes. No such collaboration exists, or is likely to in the near future, where canine health is concerned.

There is also plenty of scope for conflict of interest and little or no regulation with a predicted explosion in the availability of relatively cheap testing for dog owners.
The authors of the study are calling for:

  • The establishment of common standards in testing methodology and the reporting of test results
  • The establishment of guidelines drawn up by interested parties and which may form the basis for legislation
  • Comprehensive sharing of anonymised data
  • Recruitment of dedicated expertise to manage and analyse data
  • The development of a cadre of professional genetic counsellors to provide support and advice to owners following genetic tests with potential for affiliation with counterparts in human genetic counselling at leading academic medical centres.

Genetic testing is a vital tool for improving dog health and it would be a tragedy for dogs if commercial incentives and incomplete knowledge were to lead to it being generally discredited because it has been falsely presented. We have seen the damage being wreaked from the false information spread about vaccination. It should serve as a warning.

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