The Australian Cattle Dog is prone to PRA, Deafness, and Hip Dysplasia; all of which can be prevented though important health testing and screening. To find results on these, as well as a dog's Elbows, Patellas, Cardiac, PLL, prcd4, and CERF screenings and/or information on these genetic disorders: Go to the Orthopedic Foundation for Animals website to learn more.
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prcd-PRA
Progressive Red-Cone Degeneration & Progressive Retinal Atrophy
(Click above link to transfer to Optigen's testing website)
The genetic disorder, prcd-PRA , causes cells in the retina at the back of the eye to degenerate and die, even though the cells seem to develop normally early in life. The “rod” cells operate in low light levels and are the first to lose normal function. Night blindness results. Then the “cone” cells gradually lose their normal function in full light situations. Most affected dogs will eventually be blind. Typically, the clinical disease is recognized first in early adolescence or early adulthood. Since age at onset of disease varies among breeds, you should read specific information for your dog. Diagnosis of retinal disease can be difficult. Conditions that seem to be prcd-PRA might instead be another disease and might not be inherited. OptiGen’s genetic test assists in making the diagnosis. It’s important to remember that not all retinal disease is PRA and not all PRA is the prcd form of PRA. Annual eye exams by a veterinary ophthalmologist will build a history of eye health that will help to diagnose disease.
Prcd-PRA is inherited as a recessive trait. This means a disease gene must be inherited from each parent in order to cause disease in an offspring. Parents were either “carrier” or affected. A carrier has one disease gene and one normal gene, and is termed “heterozygous” for the disease. A normal dog has no disease gene and is termed “homozygous normal” – both copies of the gene are the same. And a dog with two disease genes is termed “homozygous affected” – both copies of the gene are abnormal.
It’s been proven that all breeds being tested for prcd-PRA have the same disease caused by the same mutated gene. This is so, even though the disease might develop at different ages or with differing severity from one breed to another.
Although prcd-PRA is inherited, it can be avoided in future generations by testing dogs before breeding. Identification of dogs that do not carry disease genes is the key. These "clear" dogs can be bred to any mate - even to a prcd-affected dog which may be a desirable breeding prospect for other reasons. The chance of producing affected pups from such breedings depends on the certainty of test results. Again, you’ll find the specific information on certainty of test results for your dog by linking to breed specific information.
The genetic disorder, prcd-PRA , causes cells in the retina at the back of the eye to degenerate and die, even though the cells seem to develop normally early in life. The “rod” cells operate in low light levels and are the first to lose normal function. Night blindness results. Then the “cone” cells gradually lose their normal function in full light situations. Most affected dogs will eventually be blind. Typically, the clinical disease is recognized first in early adolescence or early adulthood. Since age at onset of disease varies among breeds, you should read specific information for your dog. Diagnosis of retinal disease can be difficult. Conditions that seem to be prcd-PRA might instead be another disease and might not be inherited. OptiGen’s genetic test assists in making the diagnosis. It’s important to remember that not all retinal disease is PRA and not all PRA is the prcd form of PRA. Annual eye exams by a veterinary ophthalmologist will build a history of eye health that will help to diagnose disease.
Prcd-PRA is inherited as a recessive trait. This means a disease gene must be inherited from each parent in order to cause disease in an offspring. Parents were either “carrier” or affected. A carrier has one disease gene and one normal gene, and is termed “heterozygous” for the disease. A normal dog has no disease gene and is termed “homozygous normal” – both copies of the gene are the same. And a dog with two disease genes is termed “homozygous affected” – both copies of the gene are abnormal.
It’s been proven that all breeds being tested for prcd-PRA have the same disease caused by the same mutated gene. This is so, even though the disease might develop at different ages or with differing severity from one breed to another.
Although prcd-PRA is inherited, it can be avoided in future generations by testing dogs before breeding. Identification of dogs that do not carry disease genes is the key. These "clear" dogs can be bred to any mate - even to a prcd-affected dog which may be a desirable breeding prospect for other reasons. The chance of producing affected pups from such breedings depends on the certainty of test results. Again, you’ll find the specific information on certainty of test results for your dog by linking to breed specific information.
BAER
Brainsten Auditory Evoked Responses
(Click the above link to tranfer to website with all testing site locations in the U.S.)
The brainstem-auditory-evoked-response (BAER) test is the only 100% reliable method for determining that a dog is deaf. More importantly, it can accurately detect dogs that are unilaterally deaf (deaf in just one ear). Bilaterally deaf dogs are usually easy to identify as they do not respond to any noises including very loud or startling sounds. Unilateral deaf dogs are notoriously difficult to identify because they compensate very well for the loss of hearing in one ear. Dog breeding associations that recognize deafness as a problem in the breed have specific recommendations for breeding BAER tested dogs.
BAER testing detects electrical activity in the inner ear and auditory pathways in the brain in response to a click that is produced and directed into the ear with a foam insert earphone.
Deafness in the Australian Cattle Dog comes from their ancestor, the Dalmation. (Also why they are born white, except for their solid markings).
The brainstem-auditory-evoked-response (BAER) test is the only 100% reliable method for determining that a dog is deaf. More importantly, it can accurately detect dogs that are unilaterally deaf (deaf in just one ear). Bilaterally deaf dogs are usually easy to identify as they do not respond to any noises including very loud or startling sounds. Unilateral deaf dogs are notoriously difficult to identify because they compensate very well for the loss of hearing in one ear. Dog breeding associations that recognize deafness as a problem in the breed have specific recommendations for breeding BAER tested dogs.
BAER testing detects electrical activity in the inner ear and auditory pathways in the brain in response to a click that is produced and directed into the ear with a foam insert earphone.
Deafness in the Australian Cattle Dog comes from their ancestor, the Dalmation. (Also why they are born white, except for their solid markings).
Dysplastic Hip Joint
Severe Hip DysplasiaHip Dysplasia is a terrible genetic disease because of the various degrees of arthritis (also
called degenerative joint disease, arthrosis, osteoarthrosis) it can eventually produce, leading to pain and debilitation.
The very first step in the development of arthritis is articular cartilage (the type of cartilage lining the joint) damage due to the
inherited bad biomechanics of an abnormally developed hip joint. Traumatic articular fracture through the joint surface is another
way cartilage is damaged. With cartilage damage, lots of degradative enzymes are released into the joint. These enzymes degrade and decrease the synthesis of important constituent molecules that form hyaline cartilage called proteoglycans. This causes the cartilage to lose its thickness and elasticity, which are important in absorbing mechanical loads placed across the joint during movement.
Eventually, more debris and enzymes spill into the joint fluid and destroy molecules called glycosaminoglycan and hyaluronate
which are important precursors that form the cartilage proteoglycans. The joint's lubrication and ability to block inflammatory cells are lost and the debris-tainted joint fluid loses its ability to properly nourish the cartilage through impairment of nutrient-waste exchange across the joint cartilage cells. The damage then spreads to the synovial membrane lining the joint capsule and more degradative enzymes and inflammatory cells stream into the joint. Full thickness loss of cartilage allows the synovial fluid to contact nerve endings in the subchondral bone, resulting in pain. In an attempt to stabilize the joint to decrease the pain, the animal's body produces new bone at the edges of the joint surface, joint capsule, ligament and muscle attachments (bone spurs). The joint capsule also eventually thickens and the joint's range of motion decreases.
No one can predict when or even if a dysplastic dog will start showing clinical signs of lameness due to pain. Thereare multiple environmental factors such as caloric intake, level of exercise, and weather that can affect the severity of clinical signs and phenotypic expression (radiographic changes). There is no rhyme or reason to the severity of radiographic changes correlated with the clinical findings. There are a number of dysplastic dogs with severe arthritis that run, jump, and play as if nothing is wrong and some dogs with barely any arthritic radiographic changes that are severely lame.
called degenerative joint disease, arthrosis, osteoarthrosis) it can eventually produce, leading to pain and debilitation.
The very first step in the development of arthritis is articular cartilage (the type of cartilage lining the joint) damage due to the
inherited bad biomechanics of an abnormally developed hip joint. Traumatic articular fracture through the joint surface is another
way cartilage is damaged. With cartilage damage, lots of degradative enzymes are released into the joint. These enzymes degrade and decrease the synthesis of important constituent molecules that form hyaline cartilage called proteoglycans. This causes the cartilage to lose its thickness and elasticity, which are important in absorbing mechanical loads placed across the joint during movement.
Eventually, more debris and enzymes spill into the joint fluid and destroy molecules called glycosaminoglycan and hyaluronate
which are important precursors that form the cartilage proteoglycans. The joint's lubrication and ability to block inflammatory cells are lost and the debris-tainted joint fluid loses its ability to properly nourish the cartilage through impairment of nutrient-waste exchange across the joint cartilage cells. The damage then spreads to the synovial membrane lining the joint capsule and more degradative enzymes and inflammatory cells stream into the joint. Full thickness loss of cartilage allows the synovial fluid to contact nerve endings in the subchondral bone, resulting in pain. In an attempt to stabilize the joint to decrease the pain, the animal's body produces new bone at the edges of the joint surface, joint capsule, ligament and muscle attachments (bone spurs). The joint capsule also eventually thickens and the joint's range of motion decreases.
No one can predict when or even if a dysplastic dog will start showing clinical signs of lameness due to pain. Thereare multiple environmental factors such as caloric intake, level of exercise, and weather that can affect the severity of clinical signs and phenotypic expression (radiographic changes). There is no rhyme or reason to the severity of radiographic changes correlated with the clinical findings. There are a number of dysplastic dogs with severe arthritis that run, jump, and play as if nothing is wrong and some dogs with barely any arthritic radiographic changes that are severely lame.
Elbow Dysplasia
Elbow dysplasia is a general term used to identify an inherited polygenic disease in the elbow of dogs. Three specific etiologies
make up this disease and they can occur independently or in conjunction with one another.
These etiologies include:
1. Pathology involving the medial coronoid of the ulna (FCP)
2.Osteochondritis of the medial humeral condyle in the elbow joint (OCD)
3.Ununited anconeal process (UAP)
Studies have shown the inherited polygenic traits causing these etiologies are independent of one another. Clinical signs involve lameness which may remain subtle for long periods of time. No one can predict at what age lameness will occur in a dog due to a
large number of genetic and environmental factors such as degree of severity of changes, rate of weight gain, amount of exercise, etc. Subtle changes in gait may be characterized by excessive inward deviation of the paw which raises the outside of the paw so that it receives less weight and distributes more mechanical weight on the outside (lateral) aspect of the elbow joint away from the lesions located on the inside of the joint. Range of motion in the elbow is also decreased.
make up this disease and they can occur independently or in conjunction with one another.
These etiologies include:
1. Pathology involving the medial coronoid of the ulna (FCP)
2.Osteochondritis of the medial humeral condyle in the elbow joint (OCD)
3.Ununited anconeal process (UAP)
Studies have shown the inherited polygenic traits causing these etiologies are independent of one another. Clinical signs involve lameness which may remain subtle for long periods of time. No one can predict at what age lameness will occur in a dog due to a
large number of genetic and environmental factors such as degree of severity of changes, rate of weight gain, amount of exercise, etc. Subtle changes in gait may be characterized by excessive inward deviation of the paw which raises the outside of the paw so that it receives less weight and distributes more mechanical weight on the outside (lateral) aspect of the elbow joint away from the lesions located on the inside of the joint. Range of motion in the elbow is also decreased.
Patellas: Luxating Knee
The patella, or kneecap, is part of the stifle joint (knee). In patellar luxation, the kneecap luxates,
or pops out of place, either in a medial or lateral position.
Bilateral involvement is most common, but unilateral is not uncommon. Animals can be affected by the time they are 8 weeks of age. The most notable finding is a knock-knee (genu valgum) stance. The patella is usually reducible, and laxity of the medial collateral ligament may be evident. The medial retinacular tissues of the stifle joint are often thickened, and the foot can be seen to twist laterally as weight is placed on the limb.
or pops out of place, either in a medial or lateral position.
Bilateral involvement is most common, but unilateral is not uncommon. Animals can be affected by the time they are 8 weeks of age. The most notable finding is a knock-knee (genu valgum) stance. The patella is usually reducible, and laxity of the medial collateral ligament may be evident. The medial retinacular tissues of the stifle joint are often thickened, and the foot can be seen to twist laterally as weight is placed on the limb.
Cardiac
Congenital heart diseases in dogs are malformations of the heart or great vessels. The lesions characterizing congenital heart defects are present at birth and may develop more fully during perinatal and growth periods. Many congenital heart defects are thought to be genetically transmitted from parents to offspring; however, the exact modes of inheritance have not been precisely determined for all cardiovascular malformations.
Primary Lens Luxation
PLL is an important inherited disease of the eye that is associated with disintegration of the zonule fibers that hold the lens in place. Once the lens is displaced from its normal position, i.e. it “subluxates” or “luxates”, serious and often painful secondary glaucoma can occur; blindness is a common outcome. PLL is always a bilateral condition however there may be a period of several months or longer between the points when the two lenses luxate.
rcd4-PRA
rcd4-PRA Mutation Identified
The research team at the Animal Health Trust (AHT) in the UK recently has identified a PRA-causing mutation in the C2orf71gene in Gordon and Irish Setters from the UK and USA (Downs et al., Animal Genet. 2013 Apr:44(2): 169-77). Subsequently, this mutation has also been observed in additional PRA-affected breeds, including English and Llewellyn Setters, Polish Lowland Sheepdogs, Small Munsterlanders and Tibetan Terriers. OptiGen is pleased to now provide the rcd4 PRA mutation test for all these breeds-and others upon special request where rcd4 may be suspected.
rcd4-PRA is a Late Onset PRA (LOPRA)
The disease caused by the C2orf71 mutation does not typically result in vision loss until dogs are in their senior years--beyond 7 years of age. The initial data cited in the AHT publication indicate that the average age of onset of PRA symptoms in dogs that inherit two copies of the C2orf71 mutation is 10 years of age however variation in age of onset is common in many forms of PRA and some dogs may not show symptoms of rcd4-PRA until they are 12 or older.
Prevalence of the C2orf71 mutation and how to best manage breeding strategies
The frequency of the rcd4-PRA mutation may be quite high in some breeds. Downs et al. estimated that 37% of Gordon Setters from the UK carry the rcd4 mutation. Gordon Setters from the USA were roughly half as likely to carry the mutation; 18% were reported as rcd4 Carriers. A research cohort of 136 Irish Setters from 8 countries showed 29% of Irish Setters carry the rcd4 mutation. No Irish Red and White Setters were observed carrying the rcd4 mutation however the test is made available to this breed given their close ancestry with Irish Setters. The high prevalence of the rcd4 mutation within some breeds, along with the typical late age of disease onset, calls for careful consideration as one weighs the importance of rcd4 in a breeding program.
Multiple forms of PRA exist in many breeds
As our understanding of the causes of PRA grows and new mutations are identified, it has become clear that many breeds are likely to harbor more than one form of inherited PRA. This is clearly the case with the Irish Setter where a very early onset of retinal degeneration is caused by another mutation, rcd1. Dogs that are homozygous (i.e. have 2 copies of) the rcd1 mutation typically become completely blind by the time they are ~1-2 years of age. In addition to the early rcd1-PRA and the late rcd4-PRA there are also uncharacterized cases of PRA in many breeds, including the Irish Setter. OptiGen welcomes the submission of blood samples form PRA-diagnosed pedigreed dogs and tests them at no charge as a part of our ongoing PRA research program. If you have a pedigreed dog that has been diagnosed with PRA, please contact [email protected] to inquire about OptiGen's Free DNA testing and PRA research. A recent chapter, "Genetic and phenotypic variations of inherited retinal disease in dogs: The power of within-and across-breed studies." by Miyadera, Acland & Aguirre provides a useful review of this topic (Mamm Genome. 2012 Feb,23(1-2):40-61.)
The research team at the Animal Health Trust (AHT) in the UK recently has identified a PRA-causing mutation in the C2orf71gene in Gordon and Irish Setters from the UK and USA (Downs et al., Animal Genet. 2013 Apr:44(2): 169-77). Subsequently, this mutation has also been observed in additional PRA-affected breeds, including English and Llewellyn Setters, Polish Lowland Sheepdogs, Small Munsterlanders and Tibetan Terriers. OptiGen is pleased to now provide the rcd4 PRA mutation test for all these breeds-and others upon special request where rcd4 may be suspected.
rcd4-PRA is a Late Onset PRA (LOPRA)
The disease caused by the C2orf71 mutation does not typically result in vision loss until dogs are in their senior years--beyond 7 years of age. The initial data cited in the AHT publication indicate that the average age of onset of PRA symptoms in dogs that inherit two copies of the C2orf71 mutation is 10 years of age however variation in age of onset is common in many forms of PRA and some dogs may not show symptoms of rcd4-PRA until they are 12 or older.
Prevalence of the C2orf71 mutation and how to best manage breeding strategies
The frequency of the rcd4-PRA mutation may be quite high in some breeds. Downs et al. estimated that 37% of Gordon Setters from the UK carry the rcd4 mutation. Gordon Setters from the USA were roughly half as likely to carry the mutation; 18% were reported as rcd4 Carriers. A research cohort of 136 Irish Setters from 8 countries showed 29% of Irish Setters carry the rcd4 mutation. No Irish Red and White Setters were observed carrying the rcd4 mutation however the test is made available to this breed given their close ancestry with Irish Setters. The high prevalence of the rcd4 mutation within some breeds, along with the typical late age of disease onset, calls for careful consideration as one weighs the importance of rcd4 in a breeding program.
Multiple forms of PRA exist in many breeds
As our understanding of the causes of PRA grows and new mutations are identified, it has become clear that many breeds are likely to harbor more than one form of inherited PRA. This is clearly the case with the Irish Setter where a very early onset of retinal degeneration is caused by another mutation, rcd1. Dogs that are homozygous (i.e. have 2 copies of) the rcd1 mutation typically become completely blind by the time they are ~1-2 years of age. In addition to the early rcd1-PRA and the late rcd4-PRA there are also uncharacterized cases of PRA in many breeds, including the Irish Setter. OptiGen welcomes the submission of blood samples form PRA-diagnosed pedigreed dogs and tests them at no charge as a part of our ongoing PRA research program. If you have a pedigreed dog that has been diagnosed with PRA, please contact [email protected] to inquire about OptiGen's Free DNA testing and PRA research. A recent chapter, "Genetic and phenotypic variations of inherited retinal disease in dogs: The power of within-and across-breed studies." by Miyadera, Acland & Aguirre provides a useful review of this topic (Mamm Genome. 2012 Feb,23(1-2):40-61.)
Information credited to The Orthopedic Foundation for Animals