Genetic Testing & Why


By and large, we are very fortunate that Scottish Collies are pretty healthy dogs.  However, there are a few inherited diseases that have been identified as being a problem for the various Collie breeds.  It is the goal of the Scottish Collie Preservation Society to acknowledge that these harmful diseases exist; to educate our members, breeders, and the public about them; and to provide SCPS breeders with the tools and information that will ultimately enable our community to breed healthier dogs.

Genetics Primer in 156 Words

Each dog receives a specific matched set of genes at the moment of their conception: half from their dam, and half from their sire.  These genes define everything, including temperament, color, working ability, health, and 10,000 other things.  Many diseases are known as "autosomal recessive" diseases, meaning simply that a dog must inherit one copy of the gene mutation from each parent for the disease to be present in the pup; these pups are then "Affected".  If they receive one copy of the mutation from only one parent, the dog is what's known as a "Carrier" for that disease, meaning that he won't develop the disease himself, but can pass it on to his pups.  If they don't receive a copy of the mutation from either parent, they are "Clear" and will never develop that particular disease.  Below is a table that explains what to expect from puppies depending on the disease status of each parent.
 

The wonderful thing about genetics is that once you understand the simple rules of inheritance for autosomal recessive diseases (what we're mostly concerned with in the Scottish Collie), you can then seek out dogs that will help to advance the genetic profile of your own breeding program.  It takes time, determination, and a like-minded community that shares the same goal.  To that end, we earnestly hope that you will come with us in the effort to preserve the Scottish Collie.

 

DISEASES OF PRIMARY CONCERN

[ MDR1 ]  MULTI-DRUG RESISTANCE MUTATION

The brains of dogs, people, and other species contains a protein that has the job of pumping toxins out of the brains.  When a dog is MDR1 Affected, the pump is essentially "broken," while it's "out of whack" for Carriers.  Veterinary medicine has learned over the years that certain drugs can be highly dangerous for MDR1 dogs, as the mutation inhibits the body's ability to pump those drugs out of the brain.  This triggers a neurotoxicity crisis, causing all sorts of neurological symptoms for MDR1 dogs.  In some cases, it results in death.

Fortunately, we know most of the drugs that can cause problems, and which should be avoided altogether.  If you suspect that your dog is having an MDR1 reaction, it's imperative that you get him medical help immediately.  Dr. Katrina Mealey at Washington State University has given her expert consultation to local vets on treating Ivermectin toxicity.  The phone number listed for Dr. Mealey is (509) 335-2988.

[ CEA ]  COLLIE EYE ANOMALY

Collie Eye Anomaly is an inherited disease that causes an abnormality of the choroid layer that surrounds the outer layer of the back of the eye and "feeds" the retina.  In CEA, the choroid doesn't develop properly, so the retina doesn't get what it needs.  When puppies are anticipated to be possibly Affected, breeders have them evaluated at the optimal time of 6-8 weeks of age, before the the eye matures and while the canine ophthalmologist can still visualize abnormalities.  CEA-Affected dogs can experience a range of symptoms, from mild to total blindness, but many dogs experience no loss of vision at all.  For a dog to be Affected, he must inherit one copy of the mutation from both parents.  Carriers can pass on the defect to their pups, but won't manifest the disease themselves.

 

DISEASES OF SECONDARY CONCERN

[ CN ]  CYCLIC NEUTROPENIA

CN, or "Gray Collie Syndrome," is an inherited disease affecting the dog's neutrophils, which is a type of white blood cell.  Most CN dogs die within days of birth; if they survive, they are often stunted.  If they survive longer, they will have disease episodes approximately every two weeks as neutrophil counts swing from normal to zero, and then back up again.  Even when diagnosed and receiving the best of care, most surviving CN dogs die by the age of two, from either liver or kidney failure.

[ DM ]  DEGENERATIVE MYELOPATHY

This is Lou Gehrig's disease in dogs.  An extremely late-onset inherited disease, DM doesn't usually show until 9 years of age - well after most dogs are done breeding, and any mutation has been passed on to their progeny.  It's a neurological disease affecting the rear legs predominantly, with the animal losing his ability to walk within 6 months to 2 years.  The disease eventually progresses to the front legs as well.  In a study of 151 Collies, 25.8% were found to be carriers, and 25.8% were at-risk/affected.

[ PRA/PRCD ]  PROGRESSIVE RETINAL ATROPHY / PROGRESSIVE ROD-CONE DISEASE

These are late-onset inherited diseases of the eye. Affected dogs are fine until the onset of symptoms, which is usually between 3 to 5 years of age or later, often long after a dog has either produced or sired their first litter.  Problems begin with not seeing well in both dim and bright light, and progress to night blindness, and then eventually may lead to total blindness.  The progression from onset to total blindness varies, depending on the dog and possibly nutrition.

While Collies in general aren't known for PRA/PRCD, the English Shepherd is.  The ES has crossed paths with many Collie lines, so it's wise to be aware of the possibility, especially if there are known ES pairings in your dog's pedigree.

[ VWD II ]  VON WILLEBRAND'S DISEASE (TYPE II)

VWD is an inherited blood-clotting disease.  Symptoms can include easy bruising, frequent nosebleeds, lots of bleeding from teething, and excessive bleeding from surgery or trauma.  When dogs are known VWD-Affected, surgeons can be ready ahead of time with extra blood units on hand, but can be caught off guard when it's not known that a patient is Affected.  VWD could also be a problem for simple everyday concerns such as nail trims, but it's especially important for dogs who work bigger stock such as swine or cattle.

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