Dear Aimee,

Do you know if the JADD in NSDTR is simple mendelian or complex? UC Davies genetics lab is offering a test. Do you know if it is a reliable test? Do you think the test should be mandatory for NSDTR used for breeding given its early age of onset and serious impact on an affected dog's health and welfare? I would be very grateful for your comments.

Kind Regards,

Anon UK NSDTR Breeder

Dear NSDTR Breeder,

It is my understanding that the JADD (Juvenile Addison's Disease) genetic test that is available is a simple inheritance (autosomal recessive) and based on the published discovery research, it seems likely at this time that this test for the NSDTR has a 75% penetrance. According to the researchers, this means that the dog that is tested as genetically affected for JADD has a 75% risk of going on to develop the clinical signs of the disease. This is sometimes referred to autosomal-recessive, with incomplete penetrance. They don't know why 25% of genetically affected dogs don't get the disease, and they don't know for sure that this mutation is the only one associated with developing the disease. We don't yet know how "common" this disease or the risk is. This makes it difficult to know how important it is as a disease to test for. It may be worth you contacting the UK NSDTR Breed Club, as they appear to be aware of the disease, but also seem to only have noted 1 reported case in the UK. (you can find links to their club website, including health pages below) It is very possible for a disease to be more or less common in different countries.

As for UC Davis, I believe they worked closely with the research team (who is also based at UC Davis) to develop the test, so while it isn't to say that other test providers aren't also doing a good job, it is a general good idea to have the test performed by the team who discovered it, or who worked closely/collaborated, as they should be familiar with any technical challenges.  They are also, I believe still working with breeders in furthering research for this disease, so they may be hoping to have a better idea of prevalence in the future, and perhaps addressing that unknown 25% aspect. (see reference below)

As for it being a mandatory test for breeding, I guess you mean the Kennel Club registered dogs? It is hard to know. I believe the test can have value, and that the researchers are providing most of the information needed to help with breeding decisions, but it is not as black and white as a classic autosomal recessive disease, with 100% penetrance. In an ideal world, a club might organize (or researchers might somehow support/collaborate) to test dogs randomly across the population, and get some idea of how common the mutation is. This would help them determine how to prioritize testing for this disease.

If pushed, I'd probably personally test for JADD, based on the potential welfare impact, and for contributing to further research. But, not at the expense of not doing hip scoring, or tests for the more common eye conditions.

I hope that helps!

Take-away Points:

New genetic mutations are being discovered all the time. It is important to consider why you are considering genetic testing, and to prioritize what is important for your dog’s welfare, and consider what is best for the breed/population as a whole.

When a test isn’t a straightforward “simple” inheritance, it may mean that you don’t have the full-picture of the disease and its inheritance. It can still be beneficial to test – you’ll get some information about your dog, you might want to incorporate it into breeding plans, and you’ll probably be contributing to the research – especially if you are engaging with the original test developers/researchers. But, these tests will not provide any yes or no answers.

If the inheritance is complex, or the test is still essentially in a research phase, you shouldn’t necessarily prioritize a new test over the conditions and concerns that are established in your breed. If you have limited resources, focusing on established DNA tests for common diseases in your breed, any clinical screening such as hips/elbows/eyes/hearts/etc., and breeding for soundness and behavior should be your first priorities.

References/Further reading and resources:

TWO NEW DNA BASED TESTS AVAILABLE FOR THE NSDTR Written by Danika Bannasch DVM PhD; Professor Department of Population Health and Reproduction, School of Veterinary Medicine, University of California-Davis Published Spring 2012 Issue-Quacker. http://nsdtrc-usa.org/pdf_files/2012/Quakers-JADD-CP1-0512.pdf

UK-Based Breed Club, with Health resources: www.toller-club.co.uk