Common Symptoms
Progressive retinal Atrophy (sloughi type) is a late onset, inherited eye disease affecting sloughi dogs. Progressive retinal atrophy (sloughi type) occurs as a result of degeneration of both Rod and cone type Photoreceptor Cells of the Retina, which are important for vision in dim and bright light, respectively. The rod type cells are affected first and dogs present around 2-3 years of age with vision deficits in dim light (night blindness) and loss of peripheral vision. Over years affected dogs continue to lose night vision and begin to show visual deficits in bright light. Other signs of progressive retinal atrophy involve changes in reflectivity and appearance of a structure behind the retina called the Tapetum that can be observed on a veterinary eye exam. Although there is individual variation in age of onset and the rate of disease progression, the disease generally follows a slow progression and dogs may or may not become completely blind.
Testing Tips
Genetic testing of the PDE6B gene will reliably determine whether a dog is a genetic Carrier of progressive retinal Atrophy (sloughi type). Progressive retinal atrophy (sloughi type) is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of being a carrier of the PDE6B gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms do not appear until adulthood, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups. However, because there are multiple types of progressive retinal atrophy (PRA) caused by mutations in other genes, a normal result in PDE6B does not exclude PRA in a pedigree.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
References
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Crapon de Caprona, MD. [internet] Sloughi Fanciers Association of America; Progressive retinal atrophy in the Sloughi. [cited 15 April 2014] Available at http://sloughi.tripod.com/SFAA/PRA.html
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Dekomien G, Runte M, Gödde R, Epplen JT. Generalized progressive retinal atrophy of Sloughi dogs is due to an 8-bp insertion in exon 21 of the PDE6B gene.Cytogenet Cell Genet. 2000; 90(3-4):261-7.
[PubMed: 11124530]
