Animal Genetic Testing
At Cuddle Wind Yorkies, our foremost objective is to ensure the health and happiness of our puppies. To uphold this commitment, we undertake rigorous health testing protocols to identify and mitigate genetic diseases that can be inherited across generations. Among the common genetic diseases known to affect Yorkshire Terriers are Degenerative Myelopathy (DM), Primary Lens Luxation (PLL), and Progressive Retinal Atrophy (PRCD). While it is not possible to test for every potential genetic ailment, we adhere to the recommendations set forth for Yorkshire Terriers by accredited Animal Genetic testing laboratories.
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We are pleased to present below the comprehensive laboratory results for our sire, Cody Bear Lee. Cody has undergone testing for all three of the aforementioned genetic diseases, and we are pleased to report that he has tested negative and is cleared of any genetic predisposition to these conditions.
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Degenerative Myelopathy (DM) is a progressive neurological disorder that affects the spinal cord of dogs. DM is a recessive disorder; however, symptoms can present themselves even with one copy of the defective gene. If a dog has one copy of DM, they can still develop DM symptoms. However, their chance for developing symptoms is less compared to a dog with two copies of the DM mutation. Genetic testing reveals the susceptibility of dogs developing DM. It is important to note that even though a dog possesses two copies of DM, it does not mean that the dog will develop symptoms of DM. It simply means that the likelihood of the dog developing DM symptoms is much higher than average.
Dogs that have inherited two defective copies of DM will experience a breakdown of the cells responsible for sending and receiving signals from the brain, resulting in neurological symptoms. This breakdown of communication between the body and the brain can have several effects. The disease often begins with an unsteady gait, and the dog may wobble when they attempt to walk. As the disease progresses, the dog's hind legs will weaken and eventually the dog will not be unable to walk at all. Degenerative Myelopathy moves up the body. If the disease is allowed to progress, the dog will eventually be unable to hold his bladder and will lose normal function in its front legs. Fortunately, there is no direct pain associated with Degenerative Myelopathy. DM generally occurs later in life. It typically begins an average age of about 10 years. However, some dogs may begin experiencing symptoms much earlier.
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Primary Lens Luxation (PLL) is a disorder that is characterized by weakened zonular fibers which eventually lead to the dislocation of the lens in the eye. In the eye of a canine, the lens is located directly behind the iris and pupil. It is responsible for focusing light to the retina in the back of the eye. The zonular fibers are responsible for holding the lens in place.
In dogs affected by PLL, these fibers are much weaker, and the lens can dislocate or luxate. This is very painful for the dog. Depending on where the lens moves to, it can leave the dog permanently blind. Often, this event will occur around 3-6 years of age. It is recommended that all dogs genetically affected by PLL be evaluated by a veterinarian every 6 months to monitor the condition of the eyes. Primary Lens Luxation is generally an autosomal recessive disorder. Autosomal recessive disorders are disorders that can be passed from either parent and require two copies of the gene to show symptoms. However, there have been cases of a carrier dog having a luxated lens. Carriers are dogs that have one copy of the mutation responsible for PLL and can pass that mutation on to any offspring. Typically, carriers have a lesser chance of the lens luxating. It is important to test dogs to see if they carry for the PLL disorder. If two carriers are bred together, there is a 25% chance per puppy that they will develop the PLL disorder and have a higher chance of the lens luxating.
Not all cases of a luxated lens are from Primary Lens Luxation. Dogs that are genetically clear of the mutation could potentially experience this event at some point. This could be from an injury, other eye disorders, or an infection.
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Progressive Rod-Cone Degeneration, or PRA-prcd, is a form of Progressive Retinal Atrophy (PRA) in which the cells in the dog's retina in the eye degenerate and die. PRA for dogs is similar to Retinitis Pigmentosa in humans. Most affected dogs will not show signs of vision loss until 3-5 years of age. Complete blindness can occur in older dogs. Progressive Rod-Cone Degeneration is a form of PRA known to affect over 40 different breeds.
The retina is a membrane located in the back of the eye that contains two types of photoreceptor cells. These cells take light coming into the eyes and relay it back to the brain as electrical impulses. These impulses are interpreted by the brain to "create" images. In dogs suffering from PRA-prcd, the photoreceptor cells begin to degenerate, causing an inability to see changes in light. This results in a loss of vision. Rod cells, which normally function in low-light or nighttime conditions, begin to degenerate first. This leads to night-blindness. The cone cells, which normally function in bright-light or daytime conditions, will deteriorate next. This often leads to complete blindness over a period of time.
PRA-prcd is inherited as an autosomal recessive disorder. Autosomal recessive disorders are disorders that can be passed from either parent and require two copies of the gene to show symptoms. A dog must have two copies of the mutated gene to be affected by PRA. A dog can have one copy of the mutation and not experience any symptoms of the disease. Dogs with one copy of the mutation are known as carriers, meaning that they can pass on the mutation to their offspring. If they breed with another carrier, there is a 25% chance that the offspring can inherit one copy of the mutated gene from each parent and be affected by the disease.
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References
Moody JA, Famula TR, Sampson RC, Murphy KE. Identification of microsatellite markers linked progressive retinal atrophy in American Eskimo Dogs. Am J Vet Res. 2005 Nov;66(11):1900-2. [PubMed: 16334947]
Zangerl B, Goldstein O, Philp AR, Lindauer SJ, Pearce-Kelling SE, Mullins RF, Graphodatsky AS, Ripoll D, Felix JS, Stone EM, Acland GM, Aguirre GD. Identical mutation in a novel retinal gene causes progressive
rod-cone degeneration in dogs and retinitis pigmentosa in humans. Genomics. 2006 Nov; 88(5):551-63. [PubMed: 16938425]
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Farias FH, Johnson GS, Taylor JF, Giuliano E, Katz ML, Sanders DN, Schnabel RD, McKay SD, Khan S, Gharahkhani P, O'Leary CA, Pettitt L, Forman OP, Boursnell M, McLaughlin B, Ahonen S, Lohi H, Hernandez-Merino E, Gould DJ, Sargan DR, Mellersh C. An ADAMTS17 splice donor site mutation in dogs with primary lens luxation. Invest Ophthalmol Vis Sci. 2010 Sep; 51(9):4716-21. [PubMed: 20375329]
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This resource can be found on www.animalgenetics.com.
Please be advised that Cuddle Wind Yorkies disclaims any credit or responsibility for this resource.
