Health Testing

Patellar Luxation

(Slipping Kneecap)

The patellar or kneecap is a small bone buried in the tendon of the muscles of the thigh. The tendon is a band of tough, inelastic tissue that connects a muscle with its bony attachement. With this condition, the kneecap may slip out of the tendon and then slip back. Patellar luxation is graded 1 to 4 based on the severity of the defect, 1 being occasional mild lameness. As the disease progresses in duration and severity, this lameness becomes more frequent and eventually becomes continuous. In young puppies with severe patellar luxation, the rear legs often present a "bow-legged" appearance that worsens with growth.

Surgical correction of patellar luxation grades 1, 2, or 3 results generally in a successful clinical outcome, whereas surgical correction of grade 4 patellar luxations may not be as effective in young dogs.

When the luxation is left alone, it causes deformity and disorder in the growth of the affected limb. In severe cases, the limb may cease to function or cause other degenerative joint diseases (DJD) such as osteoarthritis. Early surgical correction is therefore essential, but the owners are not able to detect the disorder at an early age and surgical intervention in most cases will take place after 6 months of age.

Prcd-PRA

Progressive rod-cone degeneration (Prcd)

Progressive Retinal Atrophy (PRA)

PRA refers to a group of diseases that cause the retina of the eye to degenerate slowly over time. The result is declining vision and eventual blindness. “prcd” stands for “progressive rod-cone degeneration” which is the type of PRA known in several breeds.

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).

This table highlights all the desirable breedings that include at least one Normal/Clear parent. All other breedings are at risk of producing Affected pups with an extremely high probability of developing prcd during their lifetime. However, all dogs can be bred safely. It isn't necessary - or even desirable - to remove dogs from the breeding population. But when choosing pups to retain as potential breeding stock, it is important to select for Normal/Clear dogs and select against Affected dogs.

Possible results using the prcd test

Genotype

Risk Group

Significance For Breeding

Risk of prcd

Homozygous Normal

Homozygous

Homozygous Mutant

Normal/Clear

Carrier

Affected

Can be bred to any dog, extremely low risk of producing affesteds

Extremely Low

Extremely High

Should be bred only to a Normal/Clear to remove risk of producing affecteds

Expected results for breeding strategies using the prcd test

Parent 2 Status

Normal/Clear

Carrier

Affected

Normal/Clear

Carrier

Affected

Parent 1 Status

All = Normal/Clear

1/2 = Normal/Clear

1/2 = Carrier

All = Carrier

All = Affected

1/2 = Normal/Clear

1/2 = Carrier

1/4 = Normal/Clear

1/2 = Carrier

1/4 = Affected

1/2 = Carrier

1/2 = Affected

1/2 = Carrier

1/2 = Affected

Benefits & Limits to All Genetic Testing:

The benefits of genetic disease testing are clear. With informed breeding practices, breeders immediately can avoid producing affected pups, yet use any dog in their program regardless of genetic disease status. And since genetic testing can be done at any age, each dog’s genetic status can be known before clinical disease signs are recognized. Over several generations of selection away from the disease gene, breeders can even eliminate a disease gene completely from their line.

BUT, there are basic limits for any and all DNA genetic tests. Whether a test is mutation-based or marker-based, it identifies only the specific mutation being tested or the association between a specific marker set and the disease. For example, a mutation test detects one specific mutation in one specific gene. If there are several different mutations or several different genes that can cause the same condition, one must discover and then test for each mutation and each gene. Likewise, a marker test uses one marker or set of markers to define a specific condition. If the condition is associated with several different marker combinations, one must discover and then test for each marker combination. It can be difficult or even impossible to know how many mutations or how many marker sets exist in all the members of a specific breed. As more and more dogs are tested, previously unknown variations may come to light.

In the case of PRA, also keep in mind that not all retinal disease is PRA and not all PRA is the form currently detectable in your breed. Accurate diagnosis is essential. A dog can test as normal or carrier, yet be affected by a different type of PRA. Although more than one type of retinal degeneration probably occurs in every breed, by far the most common type of PRA for your breed is the type currently being tested by OptiGen.

Von Willebrand's Disease (vWD)

Bleeding Disorder

What is Von Willebrand's disease?

Von Willebrand's Disease is a common inherited bleeding disorder.

Clotting is a complex mechanism. In addition to platelets, clot formation is the result of a long chain of chemical reactions carried out by individual molecules called 'clotting factors.' Each factor is numbered such that factor I leads to a reaction with factor II forming a new substance. This then reacts with factor III and so on to factor XII.

In Von Willebrand's Disease, the dog is missing a substance, which helps the platelets form clots and stabilizes Factor VIII in the clotting process. This substance is called 'Von Willebrand's factor.' Because of the deficient clotting of blood, dogs with Von Willebrand's disease have excessive bleeding upon injury. This would be similar to hemophilia in humans.

Certain breeds have a higher incidence of vWD than others. German Shepherds, Doberman Pinschers, Shetland Sheepdogs, Chesapeake Bay Retrievers, German Shorthaired Pointers, Golden Retrievers, Standard Poodles, and Scottish Terriers all have a higher than normal incidence, showing that it can be inherited.

What are the symptoms?

Excessive bleeding is the main symptom. Bleeding generally occurs after a wound or surgery. In these cases, the blood simply does not clot in the normal time, and bleeding is extensive. Dog's with Von Willebrand's disease may also develop nosebleeds, or bleeding from the gums. Bleeding may also occur in the stomach or intestine in which case the stool may either have blood in it, or be black and tarry. Some dogs will have blood in their urine. Bleeding into the joints also occurs, which can cause symptoms similar to those of arthritis.

The diagnosis of Von Willebrand's is made through a test, which checks for the level of Von Willebrand's factor in the blood.

What are the risks?

These dogs, without treatment, can bleed to death following surgery, or what might be normally considered less than life threatening injuries.

What is the management?

Transfusions with blood collected from normal dogs is the only proven way to treat Von Willebrand's disease. Some dogs with Von Willebrand's disease also are hypothyroid - meaning they have lower than normal levels of thyroid hormone. These dogs will benefit from thyroid hormone replacement therapy.

Some studies have been done which suggest a drug called desmopressin acetate (DDAVP) may help dogs with a bleeding episode. The drug can be administered intranasally (into the nose) to increase clotting. There is still some controversy over whether this treatment is effective.

There is no cure for Von Willebrand's disease. Prevention through eliminating affected individuals from any breeding program is the goal of veterinary medicine today. Tests are available to determine which dogs may have this trait. All individuals with a history of this disorder in their backgrounds should be tested.

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Outlaw

Chinese Cresteds

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Shannon York

Health Testing

I feel Health testing is a huge part of breeding quality dogs. I have health tested all my dogs to ensure the health of the puppies I produce, and to provide proper precautions that once you have invested your heart and soul into one of my puppies, you will not have to face the heart break of a crippling genetic disease.

There are many breeders out there that will claim their dogs are health tested/clear and are not, demand proof as these are tactics being used by unethical breeders to sell their puppies. I am very proud to show you my dogs are tested and submit the results (good, bad or indifferent) to the Crested Health Database for all to view.

Here is the explanation of what the diseases we test for are.