Genetic Diseases Information

**New Owners, Please Read!**

These are the breed specific genetic diseases our dogs are tested for.

 

"Affected" - they carry two copies of the gene and will pass one copy of the gene on to their offspring.

"Carrier" - they carry only one copy of the gene, that they can pass on to their offspring.

"Clear" - they do not carry the genetic disease at all.

 

As a breeder, knowing your dog's genetic history makes you better informed and

able to insure the health and well-being of the dogs that you produce.

 

Collie Eye Anomaly (CEA)

 

DESCRIPTION:

Collie Eye Anomaly (CEA) is a inherited bilateral eye disease common in a number of breeds of dogs. The disorder causes abnormal development in layers of tissue in the eye under the retina called the choroid. These changes cause what is referred to as Choroidal Hypoplasia. The abnormal choroid appears pale and translucent. In most cases CEA is present at birth and can be detected in puppies as young as 4-8 weeks of age. There is currently no treatment for this disease.

 

Studies have shown that approximately 70 to 97 percent of rough and smooth collies in the United States and Great Britain have at least one copy of the mutation that causes CEA, and approximately 68 percent of Rough Collies in Sweden are affected. Border Collies are also subjected to this disorder, but at a lower percentage. CEA is also seen in Australian Shepherds, Shetland Sheepdogs, Lancashire Heelers, and other herding dogs.

 

Animal Genetics has developed a panel of six DNA markers called a "haplotype" to test for CEA. Animal Genetics is interested in developing a more comprehensive test to better distinguish those individual animals that may develop a more severe form of CEA from those that do not. Although we do not incorporate the genetic mutation Optigen claims to have an exclusive right to use into our panel, our test results using this haplotype of six DNA markers provides the same result.

Progressive Retinal Atrophy (PRA) (test is CNGA1)

 

DESCRIPTION:

Progressive Retinal Atrophy, or PRA, is a generalized disorder in which the cells in the retina of a dog's eye degenerate and die. In most cases, this eventually leads to complete blindness. PRA is the dog equivalent of retinitis pigmentosa in humans. Different forms of PRA have been reported in over 100 dog breeds and can be genetically heterogeneous both between and within breeds.

 

The retina is a membrane located in the back of the eye that contains two types of cells known as photoreceptors. These cells take light coming into the eyes and relay it back to the brain as electrical impulses. These impulses are intrepreted by the brain as vision. In dogs suffering from PRA, the photoreceptor cells begin to degenerate, causing an inability to interprete changes in light. Rod cells, which are normally function in low-light, begin to degenerate first, leading to night-blindness. The cone cells, which normally function in bright-light or daytime conditions, will deterioate next. This often leads to complete blindness over time.

 

In Shetland sheepdogs, a 4-bp deletion in exon 9 in the CNGA1 gene is associated with a breed-specific form of PRA. Not all PRA in Shelties is caused by this mutation. Additional forms of PRA can be found in Shelties.

 

PRA is inherited as an autosomal recessive disorder. A dog must have two copies of the mutated gene in order to be affected by PRA. Dogs with one copy of the mutation are known as carriers, and do not experience any symptoms of the disease. If two carriers are bred with one another, there is a 25% chance per puppy born that they will exhibit symptoms of sheltie-specific PRA, and a 50% chance per puppy born that they will be carriers of sheltie-specific PRA.

 

Degenerative Myelopathy (DM)

 

DESCRIPTION:

Degenerative Myelopathy (DM) is a progressive neurological disorder that affects the spinal cord of dogs. Dogs that have inherited two copies of the SOD1 gene and contract the disorder will experience a breakdown of the cells responsible for sending and receiving signals from the brain, resulting in neurological symptoms.

 

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 be unable to walk at all. Degenerative Myelopathy moves up the body, so 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.

 

The onset of Degenerative Myelopathy generally occurs later in life starting at an average age of about 8 years. However, some dogs may begin experiencing symptoms much earlier, some later, and a small percentage of dogs that have inherited two copies of the mutation will not experience symptoms at all. Thus, this disease is not completely penetrant, meaning that while a dog with the mutation is highly likely to develop Degenerative Myelopathy, the disease does not affect every dog that has the genotype.

**The DM genetic testing done shows whether or not a dog has the mutated SOD1 gene that can cause a dog to develop degenerative myelopathy later in life. Because a dog is tested to carry this gene DOES NOT mean the dog has the disease, or will ever have the disease, it means only that the dog carries the gene that can cause the disease.**

Multi-Drug Resistance (MDR1)

 

DESCRIPTION:

Multi-Drug Resistance Gene, (MDR) codes for a protein that is responsible for protecting the brain by transporting potentially harmful chemicals away from the brain. In certain breeds, a mutation occurs in the MDR1 gene that causes sensitivity to Ivermectin, Loperamide, and a number of other drugs. Dogs with this mutation have a defect in the P-glycoprotein that is normally responsible for transporting certain drugs out of the brain. The defective protein inhibits the dog's ability to remove certain drugs from the brain, leading to a buildup of these toxins. As a result of the accumulation of toxins, the dog can show neurological symptoms, such as seizures, ataxia, or even death.


Dogs that are homozygous for the MDR1 gene (meaning that they have two copies of the mutation) will display a sensitivity to Ivermectin and other similiar drugs. These dogs will also always pass one copy of the mutation to all potential offspring. Dogs that are heterozygous (meaning they have only one copy of the mutation) can still react to these drugs at higher doses. Also, there is a 50% chance that a dog with one copy of the mutation will pass it on to any offspring.


There are many different types of drugs that have been reported to cause problems. The following is a list of some of the drugs:

 

Ivermectin (found in heartworm medications) Loperamide (Imodium over the counter antidiarrheal agent) Doxorubicin, Vincristine, Vinblastine (anticancer agents) Cyclosporin (immunosuppressive agent) Digoxin (heart drug) Acepromazine (tranquiliser) Butorphanol ("Bute" pain control).


The following drugs may also cause problems: Ondansetron, Domperidone, Paclitaxel, Mitoxantrone, Etoposide, Rifampicin, Quinidine, Morphine.

 

von Willebrand's Disease Type 3 (vWD3)

 

DESCRIPTION:

Von Willebrand disease (vWD) is the most common inherited bleeding disorder found in dogs and humans. vWD inhibits the normal blood clotting process, causing prolonged bleeding after an injury. People with this condition often experience excessive bruising, prolonged nosebleeds, and excessive bleeding following any form of trauma, including surgery, or dental work.

 

The primary function of von Willebrand factor (vWF) a blood glycoprotein, is to bind itself to other proteins. The deficiency or failure of vWF function inhibits the blood coagulation process and causes bleeding which is most apparent in tissues having high blood flow or narrow vessels.

Von Willebrand's disease type I (vWDIII) :

In dogs (as well as in people), three separate types of vWD have been identified. Of these three types there are five different genetic mutations causing vWDs in dogs. Genetic tests have been developed to identify all five variants. Von Willebrand's disease type III (VWDIII) is transmitted as an autosomal recessive trait and is the most serious of the three. vWDIII affected animals do not produce any von Willebrand Factor protein in their blood.

 

A different genetic mutation causes vWDIII in each of the following:

Type A Scottish Terrier

Type B Shetland Sheepdog

Type C Kooikerhondje

Dermatomyositis (DMS)

 

DESCRIPTION:

Dermatomyositis (DMS) is an autoimmune disease affecting the skin and muscle that is often diagnosed in different degrees in Shetland Sheepdogs and Collies. In most case skin lesions involving hair loss and crusty scabs in areas such as the face, ear tips, legs and feet, and the tip of the tail. The disease can develop in puppies as early as 3 months of age or develop later in mature dogs. In some cases, an affected puppy’s symptoms may or may not diminish as it matures. 

In Collies DMS may affect more than just the skin. Often DMS symptoms include muscle wasting resulting in difficulty eating, drinking, and swallowing as well as an altered high-stepping gait. In Shelties muscle wasting is uncommon.

DMS is a complex or multi factorial immune disease where both genetic and environmental factors play a role in its development.  A dog with an elevated genetic risk for DMS can develop the disease following stress associated with infectious disease, vaccination or other physical or emotional stress related factors.

 

Animal Genetics offers testing developed by researchers from Clemson University. A set of genetic mutations are combined to create a haplotype measuring the risk factors for DMS. These results are combined into one genetic risk assessment. 

 

Locus A=PAN2 gene on chr 10
Locus B=MAP3K7CL gene on chr 31
Locus C=DLA-DRB1 (Dog Leukocyte Antigen) on chr 12 

All information on this page is courtesy of:

 

Animal Genetics

 

http://www.animalgenetics.us/Canine/Canine_Index.asp