Health Testing Info

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 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.

Golden Retriever PRA GR-PRA1 & GR-PRA2 is a category of genetic mutations that cause vision loss and blindness. Photoreceptor cells in the retina begin to degenerate, typically progressing from a loss of night vision to complete blindness. PRA affects many different dog breeds, and these mutations are breed-specific. In Golden Retrievers, two mutations have been identified in addition to prcd-PRA known as GR-PRA1 and GR-PRA2. Both GR-PRA1 and GR-PRA2 are inherited in an autosomal recessive manner. This means that a dog must inherit a copy of the mutation from each parent to be affected by the disorder. Dogs with one copy of the mutation will not show any signs or symptoms of PRA, however, they can still pass on that mutation to any offspring. DNA testing is important to ensure that two carriers are not mated together, as carriers of the GR-PRA mutations are asymptomatic. It is generally not recommended to remove carriers from a breeding program to maintain genetic diversity within the breed.

Ichthyosis-A is a autosomal recessive genetic mutation that affects the skin of Golden Retrievers. The mutation prevents the outer layer of the epidermis from forming properly, resulting in skin that becomes darkened and thick and flakes excessively. The name “Ichthyosis” is derived from the Greek word for fish, which describes the skin’s resemblance to fish scales. The most common symptom of ICH-A is excessive flaking of the skin. Other symptoms include areas of hardened skin and hyperpigmentation, which may make the skin appear dirty or blackened. Symptoms can be mild or severe. Evidence of the disease may be detected when the dog is still a puppy, but symptoms may take a year or more to develop. Additionally, symptoms can improve or worsen, depending on stress and hormonal cycles. Ichthyosis is generally not dangerous to a dog’s health, but can be unsightly, and uncomfortable for the dog. ICH-A is frequently related to other health issues such as yeast overgrowth and fungal infections. An affected dog will usually require more care with special shampoos and treatments. ICH-A is unfortunately quite common in Golden Retrievers, but can be identified with a simple DNA test. An affected dog would need to inherit the mutation from both parents since the mutation is autosomal recessive. Asymptomatic carriers and affected dogs can be identified prior to breeding to avoid producing an affected pup.

Muscular Dystrophy. GRMD is a mutation of the dystrophin gene that causes a deficiency of dystrophin proteins in Golden Retrievers. The lack of dystrophin proteins leads to the progressive degeneration of skeletal and cardiac muscles. The disease is similar to the human form of muscular dystrophy. Symptoms appear relatively quickly, at about six weeks to two months of age. An affected dog will exhibit muscle weakness, difficulty standing or walking normally, and difficulty swallowing, Symptoms can range from relatively mild to severe, but GRMD is generally fatal at about 6 months of age. The GRMD mutation is sex-linked and located on the X chromosome. So while both male and female dogs can be affected, GRMD is mostly a disease related to male Goldens. Females can be carriers of the mutation, however, and will not exhibit any symptoms. DNA testing to identify both male and female carriers is important to remove them from the breeding population.

Neonatal Encephalopathy with Seizures (NEwS) is an autosomal recessive disease of standard poodle puppies. Affected puppies are small and weak at birth. Many die in their first week of life. Those surviving past 1 week develop ataxia, a whole-body tremor and by 4 to 6 weeks of age, severe generalized clonic-tonic seizures. None have survived to 7 weeks of age. Cerebella from affected puppies were reduced in size. This fatal disease affects the brain of newborn puppies causing weakness and seizures and ultimately death within a few weeks of birth.  Neonatal encephalopathy is recessive — both parents must possess the gene mutation in order to produce offspring affected by the disease.  Dogs with one copy of this gene do not show symptom, but are carriers and can pass the gene to their offspring.

von Willebrand’s Disease Type I is an inherited bleeding disorder that 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. 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 I (VWDI) is transmitted as an autosomal recessive trait with variable penetrance and is the least serious of the three. The causal mutation for VWDI is a G>A substitution. The mutation reduces the normal production of von Willebrand’s factor (vWf) in affected dogs to only 5-10% of normal vWf production. This low concentration of normal vWf prevents normal blood coagulation resulting in excessive bleeding. Symptoms include: Abnormal Bleeding, Abnormal Blood Clotting, Bleeding Gums, Blood In The Feces, Blood In The Urine, Easy Bruising, Excessive Bleeding, Hematochezia, Hematoma, Hematuria, Nosebleeds, Vaginal Bleeding.

Progressive retinal Atrophy, progressive Rod-cone degeneration (PRA-prcd) is a late onset, inherited eye disease affecting many breeds of dog. PRA-prcd 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. Evidence of retinal disease in affected dogs can first be seen on an Electroretinogram around 1.5 years of age for most breeds, but most affected dogs will not show signs of vision loss until 3 to 5 years of age or later. 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. Over time affected dogs continue to lose night vision and begin to show visual deficits in bright light. 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 on a veterinary eye exam. Although there is individual and breed variation in the age of onset and the rate of disease progression, the disease eventually progresses to complete blindness in most dogs. Other inherited disorders of the eye can appear similar to PRA-prcd. Genetic testing may help clarify if a dog is affected with PRA-prcd or another inherited condition of the eye.

Osteochondrodysplasia is an inherited Musculoskeletal disease affecting dogs. Affected dogs typically present at about 3 weeks of age with stunted growth. Puppies often walk differently than unaffected littermates and stand with their feet turned out and hind legs splayed. Their legs are short and bent with enlarged joints and clubbed feet. They also have flatted rib cages and under bites, which can affect their ability to nurse and breathe. While affected dogs can survive for many years with supportive care, they will develop arthritis and will likely have breathing difficulty due to their deformed ribcages.

 

Hip Dysplasia is a terrible genetic disease because of the various degrees of arthritis (also called degenerative joint disease, arthrosis, osteoarthrosis) it can eventually produce, leading to pain and debilitation.

The very first step in the development of arthritis is articular cartilage (the type of cartilage lining the joint) damage due to the inherited bad biomechanics of an abnormally developed hip joint. Traumatic articular fracture through the joint surface is another way cartilage is damaged. With cartilage damage, lots of degradative enzymes are released into the joint. These enzymes degrade and decrease the synthesis of important constituent molecules that form hyaline cartilage called proteoglycans. This causes the cartilage to lose its thickness and elasticity, which are important in absorbing mechanical loads placed across the joint during movement. Eventually, more debris and enzymes spill into the joint fluid and destroy molecules called glycosaminoglycan and hyaluronate which are important precursors that form the cartilage proteoglycans. The joint’s lubrication and ability to block inflammatory cells are lost and the debris-tainted joint fluid loses its ability to properly nourish the cartilage through impairment of nutrient-waste exchange across the joint cartilage cells. The damage then spreads to the synovial membrane lining the joint capsule and more degradative enzymes and inflammatory cells stream into the joint. Full thickness loss of cartilage allows the synovial fluid to contact nerve endings in the subchondral bone, resulting in pain. In an attempt to stabilize the joint to decrease the pain, the animal’s body produces new bone at the edges of the joint surface, joint capsule, ligament and muscle attachments (bone spurs). The joint capsule also eventually thickens and the joint’s range of motion decreases.

No one can predict when or even if a dysplastic dog will start showing clinical signs of lameness due to pain. There are multiple environmental factors such as caloric intake, level of exercise, and weather that can affect the severity of clinical signs and phenotypic expression (radiographic changes). There is no rhyme or reason to the severity of radiographic changes correlated with the clinical findings. There are a number of dysplastic dogs with severe arthritis that run, jump, and play as if nothing is wrong and some dogs with barely any arthritic radiographic changes that are severely lame.

The Three Faces of Elbow Dysplasia

Elbow dysplasia is a general term used to identify an inherited polygenic disease in the elbow of dogs. Three specific etiologies make up this disease and they can occur independently or in conjunction with one another. These etiologies include:

  1. Pathology involving the medial coronoid of the ulna (FCP)
  2. Osteochondritis of the medial humeral condyle in the elbow joint (OCD)
  3. Ununited anconeal process (UAP)

Studies have shown the inherited polygenic traits causing these etiologies are independent of one another. Clinical signs involve lameness which may remain subtle for long periods of time. No one can predict at what age lameness will occur in a dog due to a large number of genetic and environmental factors such as degree of severity of changes, rate of weight gain, amount of exercise, etc. Subtle changes in gait may be characterized by excessive inward deviation of the paw which raises the outside of the paw so that it receives less weight and distributes more mechanical weight on the outside (lateral) aspect of the elbow joint away from the lesions located on the inside of the joint. Range of motion in the elbow is also decreased.

What is Patellar Luxation?

The patella, or kneecap, is part of the stifle joint (knee). In patellar luxation, the kneecap luxates, or pops out of place, either in a medial or lateral position.

Bilateral involvement is most common, but unilateral is not uncommon. Animals can be affected by the time they are 8 weeks of age. The most notable finding is a knock-knee (genu valgum) stance. The patella is usually reducible, and laxity of the medial collateral ligament may be evident. The medial retinacular tissues of the stifle joint are often thickened, and the foot can be seen to twist laterally as weight is placed on the limb.

Congenital heart diseases in dogs are malformations of the heart or great vessels. The lesions characterizing congenital heart defects are present at birth and may develop more fully during perinatal and growth periods. Many congenital heart defects are thought to be genetically transmitted from parents to offspring; however, the exact modes of inheritance have not been precisely determined for all cardiovascular malformations.

Genetics of inherited eye disease

Genetic diseases are those that are passed on from parent to offspring through genes that carry the codes for each specific trait. Many of the diseases and disorders that affect the eyes have genetic factors.

How do we identify an inherited eye disease?

Although there are noteworthy exceptions, most of the ocular diseases of dogs which are presumed to be hereditary have not been adequately documented. Genetic studies require examination of large numbers of related animals in order to characterize the disorder (age of onset, characteristic appearance, rate of progression) and to define the mode of inheritance (recessive, dominant). In a clinical situation, related animals are frequently not available for examination once a disorder suspected as inherited is identified in an individual dog. Maintaining a number of dogs for controlled breeding trials through several generations is a long and costly process. Both of these obstacles are compounded by the fact that many ocular conditions do not develop until later in life. Until the genetic basis of an ocular disorder is defined in a peer-reviewed published report, we rely on what statistical information is available from registry organizations, informed opinions and consensus from ACVO diplomates. We must satisfy ourselves with terms like “presumed inherited” and “suspected to be inherited.” Several companies provide information on genetic testing and greatly assist in providing more information and data to aid in defining the canine genetics of ocular diseases.

There are eye diseases in the dog for which there is evidence of a genetic or heritable cause. The American College of Veterinary Ophthalmologists has listed ten of these diseases as automatic “fails” (this means the affected dog is ineligible to receive an eye certification) because of the significance of the condition to vision and/or the very strong evidence of heritability.

Congenital Cardiac Disease and the OFA

Congenital heart diseases in dogs are malformations of the heart or great vessels. The lesions characterizing congenital heart defects are present at birth and may develop more fully during perinatal and growth periods. Many congenital heart defects are thought to be genetically transmitted from parents to offspring; however, the exact modes of inheritance have not been precisely determined for all cardiovascular malformations.