Retinopathy in the Swedish Vallhund.
Retinopathy in the Swedish Vallhund is a form of progressive retinal atrophy that has a very variable age of onset. A DNA test for this is available at the AHT from the 1st of February 2017
A previous study showed an association with a region of DNA containing a gene in which mutations have been shown to cause retinal degeneration in humans and rodents.
Following on from this study, the Animal Health Trust has identified a mutation that is very strongly associated with retinopathy in the Swedish Vallhund. A DNA test for this mutation is now available at the Animal Health Trust DNA testing service.
How common is the disease?
The Swedish Vallhund retinopathy mutation appears to be very common in the sample sets that we have studied from both the UK and Finland.
However, due to the non-random ascertainment of the sample collections used in our research study, we cannot currently give an accurate estimation of the frequency of the mutation. Following the launch of the test we will work with the breed to obtain an estimate of the frequency of this mutation in the Swedish Vallhund.
In the first 4 month of testing (1/2/2017-26/6/2017) we tested 212 dogs.
28 dogs gave an affected result, 119 dogs gave a carrier result and 68 dogs gave a normal results.
How is the disease inherited?
The disorder appears to show an autosomal recessive mode of inheritance. This means that a dog will only develop the disease, associated with the mutation being tested, if it has two copies of the associated mutation (one inherited from each parent).
Individuals with one copy of the mutation and one copy of the normal gene, called carriers, are unlikely to show signs of disease but will pass the mutation onto around half of their offspring.
When two carriers are mated, 25% (on average) of the offspring may be affected by the disease, 25% will likely be clear and the remaining 50% will themselves be carriers.
Breeders using our retinopathy DNA test will be sent results identifying their dog as belonging to one of three categories. In all cases the terms ‘normal’ and ‘mutation’ refer to the position in the DNA where this retinopathy mutation is located; it is not possible to learn anything about any other region of DNA from this retinopathy test.
Our test only detects this specific mutation; there maybe additional forms of retinopathy in the Swedish Vallhund that are caused by different mutations. These cannot be detected by this test.
CLEAR: these dogs have two normal copies of DNA. Clear dogs will not develop retinopathy as a result of this mutation.
CARRIER: these dogs have one copy of the mutation and one normal copy of DNA. These dogs will not develop retinopathy themselves as a result of this mutation but they will pass the mutation on to approximately 50% of their offspring.
GENETICALLY AFFECTED: these dogs have two copies of this retinopathy mutation and are very likely to develop retinopathy during their lifetime.
We cannot exclude the possibility that the tested dog may develop a form of retinopathy due to other mutations they might carry that are not detected by this test.
Our research has indicated that the frequency of this retinopathy mutation in Swedish Vallhunds is high.
The mutation is recessive which means that all dogs can be bred from safely but carriers and genetically affected dogs should only be bred to DNA tested, clear dogs.
About half the puppies from any litter that has a carrier parent will themselves be carriers and any dogs from such litters that will be used for breeding should themselves be DNA tested prior to breeding so appropriate mates can be selected.
All puppies that have one genetically affected parent will be carriers.
It is advisable for all breeding dogs to have their eyes clinically examined by a veterinary ophthalmologist prior to breeding and throughout their lives so that any cases of retinopathy in dogs not carrying this mutation can be identified and newly emerging conditions can be identified.
The results for this test are reported directly to the Kennel Club.
For more information please contact us and we’ll be happy to deal with your enquiry.
Photo by Marc Henry