Genetic Disease Commonly Affecting Collies

DreamChaser tests for Collie Eye Anomaly (CEA); Progressive Retinal Atrophy - rod-cone dysplasia type 2 (PRA-rcd2); Degenerative Myelopathy (DM); and Multi-Drug Resistance 1 (MDR1). When you purchase a collie puppy or adult from us, you will get a copy of all genetic reports that are relevant for that puppy or dog. We are constantly striving to better our breeding program and work towards collies that are genetically clear of all four(4) disorders listed. Scroll down to learn more about these diseases.

Collie Eye Anomaly (CEA)

Collie eye anomaly, also referred to as collie eye defect, is an inherited congenital condition. The chromosomes that determine the development of the eyes are mutated, so that the choroid (the collection of blood vessels that absorb scattered light and nourish the retina) is underdeveloped. The mutation can also result in other defects in the eye with more severe consequences, such as retinal detachment. When this mutation does occur, it is always in both eyes, although it might be more severe in one eye than the other. Approximately 70 to 97 percent of rough and smooth collies in the United States and Great Britain are affected. The cause of collie eye anomaly is a defect in chromosome 37. It only occurs in animals that have a parent, or parents, that carry the genetic mutation. The parents may not be affected by the mutation, and may therefore not have been diagnosed with the abnormality, but offspring can be affected, especially when both parents carry the mutation. However, parents that have tested clear for CEA, meaning they do not carry the mutation, will never pass the gene onto their offspring.

 

Progressive Retinal Atrophy - rod-cone dysplasia type 2 (PRA-rcd2)

Progressive retinal Atrophy, Rod-cone dysplasia 2 is an early-onset, inherited eye disease affecting dogs. Progressive retinal atrophy, rod-cone dysplasia 2 occurs as a result of degeneration of both rod and cone type Photoreceptor Cells of the Retina, which are important for vision in dim and bright light, respectively. Affected dogs have abnormal thinning and degeneration of the retina beginning around 16 days of age. The rod type cells are affected first and affected dogs will initially have vision deficits in dim light (night blindness) and loss of peripheral vision noticeable at about 6 weeks of age. Other signs of progressive retinal atrophy involve changes in reflectivity and appearance of a structure behind the retina called the Tapetum that can be observed at 3.5-4 months of age on a veterinary eye exam. As the disease progresses, cone photoreceptor cells also degenerate resulting in complete blindness by 6 to 8 months of age. It only occurs in animals that have a parent, or parents, that carry the genetic mutation. The parents may not be affected by the mutation, and may therefore not have been diagnosed with the abnormality, but offspring can be affected, especially when both parents carry the mutation. However, parents that have tested clear for PRA-rcd2, meaning they do not carry the mutation, will never pass the gene onto their offspring.

 

Degenerative Myelopathy (DM)

Degenerative myelopathy is a progressive disease of the spinal cord in older dogs. The disease has an insidious onset typically between 8 and 14 years of age. It begins with a loss of coordination (ataxia) in the hind limbs. The affected dog will wobble when walking, knuckle over or drag the feet. This can first occur in one hind limb and then affect the other. As the disease progresses, the limbs become weak and the dog begins to buckle and has difficulty standing. The weakness gets progressively worse until the dog is unable to walk. The clinical course can range from 6 months to 1 year before dogs become paraplegic. If signs progress for a longer period of time, loss of urinary and fecal continence may occur and eventually weakness will develop in the front limbs. Another key feature of DM is that it is not a painful disease.

 

Multi-Drug Resistance 1 (MDR1)

MDR1 or Multi-drug Resistance 1 is a genetic mutation found in many of the herding breeds, some sighthound breeds, and many mixed dogs. This mutation can have a significant impact on drug sensitivity. The MDR1 gene is responsible for production of a protein called P-glycoprotein. The P-glycoprotein molecule is a drug transport pump that plays an important role in limiting drug absorption and distribution (particularly to the brain) and enhancing the excretion/ elimination of many drugs used in dogs. As a result, dogs with the MDR1-mutation may have severe adverse reactions to some common drugs. Collies and Collie mixes are highly likely to be affected with the MDR1 gene. Be sure to let your veterinarian know the status of your Collie's MDR1 genetic test so they can properly prescribe the best care without putting your Collie at risk of a reaction to medications or vaccinations.