PRA Disease
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. Unfortunately, at this time there is no treatment or cure for PRA. If your dog is affected, you may find it helpful to read about other owners’ experiences living with blind dogs. (suggested links:www.eyevet.org and www.blinddogs.com)
Inheritance
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 Test
The OptiGen prcd test is done on a small sample of blood from the dog. The test analyzes the specific DNA mutation
causing prcd-PRA. The OptiGen test detects the mutant, abnormal gene copy and the normal gene copy. The result of the test is a genotype and allows separation of dogs into three groups: Normal/Clear (homozygous normal), Carrier (heterozygous) and Affected (homozygous mutant).
MDR1 FAQs
Australian Shepherds, along with several other mostly collie-type breeds, can carry a genetic mutation that makes them sensitive to certain drugs. Use of those drugs can cause serious neurological illness or death.
Fortunately, there is an extremely accurate DNA test that will let you know whether your dog has this mutation. All you have to do is provide a cheek swab. It isn't even necessary to go to the vet.
What is MDR1?
MDR1 is the abbreviated name of a gene called Multi-Drug Resistance 1. A mutation of this gene causes sensitivity to Ivermectin and a number of other drugs. Dogs with the mutation will react to those drugs. Having two copies of the mutation will lead to drug reactions, but having a single copy can also confer some sensitivity with some drugs. Dogs with this mutation have a transport defect - the drug goes in to their brains, fails to be transported out, and builds up to toxic levels. This causes serious neurological problems including seizures and sometimes death.
Which drugs cause reactions?
Ivermectin was the first drug recognized to cause a reaction, but it is far from the only one. Ivermectin at low dosage, as found in heartworm medications, will not cause a reaction. The larger doses needed for worming will. Other commonly administered drugs on the list include acepromazine and Imodium. Fortunately, there are alternative medications available if your dog requires treatment.
The drugs involved can be found on the website below.
http://www.vetmed.wsu.edu/depts-VCPL/drugs.aspx
This site offers a "medic alert" type collar tag for MDR1 dogs and has more extensive list, including alternate and generic names for the drugs:
http://www.busteralert.com
Dogs that do not carry an MDR1 mutation may safely receive the listed drugs.
Heridetary Catarcts
Cataracts are one of the Australian Shepherd's most common hereditary problems and easily the breed's most common inherited eye disease. In March of this year, at the world-famous Crufts Dog Show in Birmingham, England, Britain's Animal Health Trust (AHT,) a century-old charitable foundation dedicated to improving diagnosis and treatment of disease for dogs, cats and horses, announced a new DNA test for hereditary cataract (HC) in the Australian Shepherd. The international breed community solidly supported the study while it was in progress. Aussie owners and breeders in the UK, North America and Europe submitted samples from over 400 dogs. AHT researchers found a mutation in a gene called HSF4 which is significantly associated with cataracts in Aussies. They subsequently developed a DNA screening test for that mutation. This test is a tool that can enable breeders to drastically reduce the frequency of cataracts in the breed.
That we have the test at all was due to a stroke of good luck. Dr. Cathryn Mellersh and her team initially found the mutation that causes HC in Staffordshire Bull Terriers, a recessive mutation of a gene called HSF4. They decided to screen all the other breeds for which they had DNA samples from dogs with cataracts to see if any shared the Staffy Bull mutation. One of those breeds was the Australian Shepherd; DNA from seven Aussies with cataracts had been stored several years before. Although Aussies didn't carry the Staffy Bull mutation, to Dr. Mellersh's surprise, they did carry another mutation in the HSF4 gene. To validate this initial result, she began to collect additional Aussie samples, first from dogs in the United Kingdom and later from North America and Europe. Ultimately, she determined that her inadvertent discovery was associated with cataracts in the breed and was able to develop a DNA test for the Australian Shepherd.
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. Unfortunately, at this time there is no treatment or cure for PRA. If your dog is affected, you may find it helpful to read about other owners’ experiences living with blind dogs. (suggested links:www.eyevet.org and www.blinddogs.com)
Inheritance
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 Test
The OptiGen prcd test is done on a small sample of blood from the dog. The test analyzes the specific DNA mutation
causing prcd-PRA. The OptiGen test detects the mutant, abnormal gene copy and the normal gene copy. The result of the test is a genotype and allows separation of dogs into three groups: Normal/Clear (homozygous normal), Carrier (heterozygous) and Affected (homozygous mutant).
MDR1 FAQs
Australian Shepherds, along with several other mostly collie-type breeds, can carry a genetic mutation that makes them sensitive to certain drugs. Use of those drugs can cause serious neurological illness or death.
Fortunately, there is an extremely accurate DNA test that will let you know whether your dog has this mutation. All you have to do is provide a cheek swab. It isn't even necessary to go to the vet.
What is MDR1?
MDR1 is the abbreviated name of a gene called Multi-Drug Resistance 1. A mutation of this gene causes sensitivity to Ivermectin and a number of other drugs. Dogs with the mutation will react to those drugs. Having two copies of the mutation will lead to drug reactions, but having a single copy can also confer some sensitivity with some drugs. Dogs with this mutation have a transport defect - the drug goes in to their brains, fails to be transported out, and builds up to toxic levels. This causes serious neurological problems including seizures and sometimes death.
Which drugs cause reactions?
Ivermectin was the first drug recognized to cause a reaction, but it is far from the only one. Ivermectin at low dosage, as found in heartworm medications, will not cause a reaction. The larger doses needed for worming will. Other commonly administered drugs on the list include acepromazine and Imodium. Fortunately, there are alternative medications available if your dog requires treatment.
The drugs involved can be found on the website below.
http://www.vetmed.wsu.edu/depts-VCPL/drugs.aspx
This site offers a "medic alert" type collar tag for MDR1 dogs and has more extensive list, including alternate and generic names for the drugs:
http://www.busteralert.com
Dogs that do not carry an MDR1 mutation may safely receive the listed drugs.
Heridetary Catarcts
Cataracts are one of the Australian Shepherd's most common hereditary problems and easily the breed's most common inherited eye disease. In March of this year, at the world-famous Crufts Dog Show in Birmingham, England, Britain's Animal Health Trust (AHT,) a century-old charitable foundation dedicated to improving diagnosis and treatment of disease for dogs, cats and horses, announced a new DNA test for hereditary cataract (HC) in the Australian Shepherd. The international breed community solidly supported the study while it was in progress. Aussie owners and breeders in the UK, North America and Europe submitted samples from over 400 dogs. AHT researchers found a mutation in a gene called HSF4 which is significantly associated with cataracts in Aussies. They subsequently developed a DNA screening test for that mutation. This test is a tool that can enable breeders to drastically reduce the frequency of cataracts in the breed.
That we have the test at all was due to a stroke of good luck. Dr. Cathryn Mellersh and her team initially found the mutation that causes HC in Staffordshire Bull Terriers, a recessive mutation of a gene called HSF4. They decided to screen all the other breeds for which they had DNA samples from dogs with cataracts to see if any shared the Staffy Bull mutation. One of those breeds was the Australian Shepherd; DNA from seven Aussies with cataracts had been stored several years before. Although Aussies didn't carry the Staffy Bull mutation, to Dr. Mellersh's surprise, they did carry another mutation in the HSF4 gene. To validate this initial result, she began to collect additional Aussie samples, first from dogs in the United Kingdom and later from North America and Europe. Ultimately, she determined that her inadvertent discovery was associated with cataracts in the breed and was able to develop a DNA test for the Australian Shepherd.