Aussie Genetics

Below are a list of items that can be found in Aussies.  Only some Aussies will be diagnoses with any of these conditions, but if you are interested in a Australian shepher puppy as a part of your family, you should be aware of the possibilities.

Cone Degenerations (CD)

Cone Degeneration (CD) is an autosomal recessive disease that occurs in the German Shorthaired Pointer, the Alaskan Malamute, and several other breeds. Cone Degeneration disease causes day-blindness. This is caused by a lack of cone function in the retina of the eye.
CD disease causes degeneration of the retinal "cones" that respond primarily to bright daylight, resulting in what is referred to as "day blindness." Cone-degenerate pups develop day-blindness and photophobia between 8 and 12 weeks of age - the age when retinal development is normally completed in dogs. Symptoms of CD are present only in bright light and the dog's vision is not affected in dim light.
Cone Degeneration is inherited as a recessive disorder. Dogs with one copy of this mutation are known as carriers. Dogs that are carriers typically do not show any symptoms of the disease. These dogs can still pass on a copy of the mutation to any offspring. If two carriers are bred, there is a 25% chance per puppy born that it will develop symptoms of CD.

Collie Eye Anomaly (CEA)

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. Aapproximately 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. Optigen claims to have an exclusive right to test for a particular genetic mutation related to this disorder. Although Animal Genetics does not include this mutation in our panel, our test uses this haplotype of six DNA markers provides the same result Optigen provides.

Canine Multifocal Retinopathy

Canine Multifocal Retinopathy Type 1 and 2 (CMR1 and CMR2) is an autosomal recessive eye disorder known to affect Great Pyrenees, English Mastiffs, Bullmastiffs, Australian Shepherds, Dogue de Bordeaux, English Bulldogs, American Bulldogs, Coton de Tulears, Perro de Presa Canario, and Cane Corsos.
The mutation causes raised lesions to form on the retina. The lesions alter the appearance of the eye but usually do not affect sight. The lesions may disappear, or may result in minor retinal folding. Symptoms of the mutation usually appear when a puppy is only a few months old, and generally do not worsen over time.
CMR is a recessive disorder. This means that a dog must inherit two copies of the mutation in order to exhibit symptoms of CMR. A dog with one copy of the mutation is known as a carrier. If two carriers are bred to one another, there is a 25% chance per puppy born that they will develop symptoms of CMR and a 50% chance per puppy born that they will also be carriers. Therefore, it is useful to test for the presence of the CMR mutation before breeding. Additionally, since retinal defects can be caused by other conditions, testing can verify that a dog actually has CMR rather than some other eye condition.

Degenerative Myelopathy (DM)

Degenerative Myelopathy (DM) is a progressive neurological disorder that affects the spinal cord of dogs. Dogs that have inherited two defective copies 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 10 years. However, some dogs may begin experiencing symptoms much earlier. A 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 likely to develop Degenerative Myelopathy, the disease does not affect every dog that has the genotype.

Hereditary Cataracts (HC)

Hereditary Cataracts (HC) are a clouding of the lens of the eye caused by a breakdown of tissue in the eye. This condition
generally results in an inability to see clearly and can cause total blindness. In canines, cataracts are often familial; this type is known as Hereditary Cataracts. A mutation in the HSF4 gene causes this type of cataracts in several breeds of dogs. In this case, the dog is typically affected bilaterally, in that both eyes are affected by the cataracts. The cataracts associated with HSF4 also occur in the posterior region of the lens. They usually start by being small and grow progressively, though the speed of growth is highly variable. Some cataracts will grow so slowly that the dog's vision remains relatively clear, while others will grow such a way that the dog will quickly go blind. Corrective surgery is possible, though it is costly and is not always effective.
A mutation of the HSF4 gene is linked to a form of Hereditary Cataracts in Australian Shepherds. This mutation affects Aussies differently then Boston Terriers, French Bulldogs and Staffordshire Bull Terriers in that the disease is dominant but not completely penetrant. This means that only one copy of the mutation is necessary to predispose a dog to the disease. However, incomplete penetrance means that a dog that has this mutation will not always develop HC. Research suggests that the mutation makes a dog 12 times more likely to develop posterior bilateral cataracts at some point in their lifetime. It is likely that a secondary gene interaction occurs in the small percentage of dogs possessing the HC mutation but does not develop cataracts. This interaction is not yet understood.
It should also be noted that not all cataracts are hereditary. Cataracts can also be caused by old age or injury. Also, cataracts that occur in different regions of the lens can also be familial, however, are not attributed to this gene mutation.

PRA

Progressive Rod-Cone Degeneration, or PRA-prcd, is a form of Progressive Retinal Atrophy (PRA) in which the cells in the dog's retina 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 photoreceptors begin to degenerate, causing an inability to interpret 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. 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.