Early Onset PRA (EOPRA) Test for Portuguese Water Dogs Code 319
PWD breeders are perhaps one of the most well aware groups of people when it comes to Progressive Retinal Atrophy, thanks to the historic prevalence of another form of PRA - progressive rod cone degeneration (prcd) -- in the breed. The PWDCA's education outreach on prcd-PRA serves as a shining example of how successful a breed club can be in improving a breed's health through making members aware of inherited disease as well as supporting basic research to allow a DNA test to be developed that will allow breeders to assure that no affected puppies are produced. OptiGen and the research team at Cornell University led by Drs. Gus Aguirre and Greg Acland worked closely with the PWDCA in the hunt for the prcd mutation through the late 90s and early 2000's. At that time, the prevalence of the prcd form of PRA in the breed was distressingly high and due to the relatively late onset of clinical signs of this form of PRA, carriers of the mutation were not obvious until after multiple litters had been produced. DNA testing for prcd offered the breed an essential means of avoiding the disease while still protecting valuable blood lines and likely helped save the breed from serious decline.
Fortunately for the breed, the EOPRA is not nearly as common as prcd --- possibly due in part to its comparably much earlier expression of clinical signs. It is not yet known what the frequency of the EOPRA mutation is in the general PWD population however as DNA testing becomes available, this information will become evident and OptiGen will openly share it with the PWD community. EOPRA has typically been diagnosed by veterinary ophthalmologists during routine eye exams when PWDs are younger than 4 years of age, however the slowly progressive change in vision may not be obvious in some cases. Both prcd and EOPRA share standard PRA clinical expression, e.g. initial hyper-reflectivity of the fundus (back of the eye) due to the thinning retina as photoreceptor cells die, followed by attenuation of blood vessels that feed the retina. Eventually, as more of the photoreceptors die, the affected dogs become completely blind. The main obvious difference between the two diseases is the age of which retinal degeneration becomes evident.
Early Onset PRA Cases that are not due to the newly identified EOPRA mutation:
EOPRA mutation based test:
The DNA-based EOPRA test allows genotype determination of a tested dog as being:
NORMAL - the dog has two copies of the normal gene and it is not going to develop Early Onset PRA caused by the EOPRA mutation.
CARRIER - the dog has one copy of the normal gene and one copy of the EOPRA mutation. The dog will not develop clinical signs of Early Onset PRA due to the EOPRA mutation but it will transmit one of the EOPRA mutation to about 50% of its progeny.
AFFECTED - the dog has two copies of the EOPRA mutation and is expected to develop/is already showing symptoms of the Progressive Retinal Degeneration caused by the EOPRA mutation.
Testing and Breeding Recommendations:
By selecting the mate with the appropriate genotype, it is possible to breed affected or carrier dogs and never produce affected progeny. In this manner the genetic diversity of the breed can be maintained.
Page last updated November 21, 2017
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