Degenerative myelopathy (DM) is an inherited neurological disorder found in many dog breeds but most commonly seen in German Shepherd Dogs and Pembroke Welsh Corgis. It is not yet clear if all dogs carrying two copies of the mutation will develop clinical signs, especially considering the variable presentation noted amongst breeds found to carry it. Clinical signs develop at an old age and all affected dogs do not develop symptoms during their natural lifespan. It is unclear, whether the disease process is ongoing in these dogs or if the mutation does not cause disease in all affected dogs. DM is inherited in an autosomal recessive fashion.
Dental hypomineralisation is a hereditary dental disease that is caused by abnormal mineralisation of teeth during dental development. The disease causes abnormal tooth wear, pulpitis and tooth loss. The disorder has been described in Border Collies. The genetic defect is estimated to be relatively common within the breed with approximately 11% of the breed population being carriers. The mode of inheritance is autosomal recessive.
Early Adult Onset Deafness (linked marker test)
Early Adult Onset Deafness (EAOD; also known as Adult Onset Deafness [AOD] or Early Onset Deafness [EOD]) is an autosomal recessive hearing disease that is relatively common in Border Collies. The gradual hearing loss is observed usually at the age of 5 to 7 years affecting both ears.
Goniodysgenesis and glaucoma
Goniodysgenesis and glaucoma in Border Collie (GDD) is a hereditary disorder affecting the eyes. Primary glaucoma is a hereditary ocular disorder affecting intraocular fluid circulation and causing increased intraocular pressure. The elevated intraocular pressure damages the optic nerve and retinal cells and leads to blindness if untreated. Glaucoma can be preceded by goniodysgenesis, which is a developmental abnormality of the anterior chamber of the eye that has been associated with glaucoma and blindness. Glaucoma affects multiple breeds, but in most cases the causative mutation has not been identified. The underlying mutation causing glaucoma and goniodysgenesis in Border Collies has been located to OLFML3 gene. The condition in inherited as an autosomal recessive trait.
Intestinal cobalamin malabsorption or Imerslund-Gräsbeck syndrome (IGS) is a metabolic disorder encountered in several breeds. Failure to absorb cobalamin in the small intestine results in retarded growth, anaemia, and neutropenia. The underlying cause for intestinal cobalamin malabsorption is a defect in cobalamin receptors in the ileum. Causative mutations have been identified in the AMN (amnionless) and CUBN (cubilin) genes. The disorder is inherited in an autosomal recessive manner.
Neuronal Ceroid Lipofuscinosis 5
Neuronal ceroid lipufuscinoses (NCLs) are a group of inherited progressive neurodegenerative lysosomal storage disorders. Neuronal ceroid lipofuscinoses are characterised by excessive accumulation of lipofuscin and ceroid lipopigments into central nervous system and other tissues. Different forms of NCL differ by age of onset and pattern of progression. Usually progressive loss of vision is the first observable symptom. In addition, the clinical signs of NCL include ataxia (uncoordinated movements), seizures and behavioural changes, such as aggression. Type 5 form of NCL is encountered in Border Collie. Neuronal ceroid lipofuscinosis type 5 is inherited in an autosomal recessive manner.
Collie Eye Anomaly
Collie Eye Anomaly (CEA) is a congenital hereditary ocular disease found in multiple breeds of herding descent. The severity of the disease varies greatly between dogs and mildly affected dogs can have puppies that are severely affected and vice versa. The disorder is inherited in an autosomal recessive manner.
Sensory neuropathy is a rare, severe neurological disorder caused by the degeneration of nerve cells. Clinical signs emerge in puppyhood. Affected dogs have proprioceptive deficits and harm themselves due to lack of pain sensation. The disorder is inherited in an autosomal recessive manner.
Trapped neutrophil syndrome
Trapped neutrophil syndrome (TNS) is a white blood cell disorder in Border Collies. TNS follows an autosomal recessive mode of inheritance. TNS is a severe disease and affected dogs have a shorter life expectancy.
Multi-Drug Resistance 1
Multi-drug resistance 1 (MDR1) is a genetic mutation that alters a dog's ability to limit the absorption and distribution of many drugs. Affected dogs are slower to eliminate drugs from the body and can suffer side effects when exposed to certain medications. This mutation is sometimes also called "ivermectin sensitivity". However, the name is a misnomer as several other drugs pose a risk to MDR1 positive dogs. Adverse reactions can occur when affected dogs are exposed to some common drugs such as acepromazine, butorphanol, and macrocyclic lactones. However, all FDA approved heartworm preventatives are safe to administer to MDR1 positive dogs. This mutation is inherited in a dominant fashion though dogs with two copies of the mutation will exhibit more severe clinical signs.
Hyperuricosuria (HUU) is an inherited disorder in dogs that can cause hyperuricemia and predisposes affected dogs to the development of urolithiasis (urate stones) in the kidneys and bladder. The disease is very common in Dalmatians but is seen in several other breeds as well. Hyperuricosuria is inherited in an autosomal recessive manner.
Primary Lens Luxation
Primary lens luxation (PLL) is an inherited condition in dogs that can cause displacement of the ocular lenses. The disorder is caused by degeneration of the zonular fibres that are required for attachment of the lens. When the lens luxates, it may do so either anteriorly or posteriorly. PLL most closely follows an autosomal recessive mode of inheritance though heterozygous dogs also have a low risk of developing PLL.
Maligant hyperthermia (MH) is an inherited disorder of skeletal muscle characterized by hypercarbia, rhabdomyolysis, generalized skeletal muscle contracture, cardiac dysrhythmia, and renal failure, that develops on exposure to succinylcholine or volatile anesthetic agents. Specific interventions, including use of the calcium release channel antagonist dantrolene, are efficacious in reversing signs of the canine syndrome. This genetic factor is inherited in an autosomal dominant fashion.
Cystinuria Type II-A
Dogs with cystinuria are not able to reabsorb the amino acid cystine in their kidneys and therefore high concentrations can accumulate in the urinary tract causing formation of cystine crystals and stones that can obstruct the urinary tract. While cystinuria has been reported in a number of breeds, this variant is known to cause the condition in Australian Cattle Dogs. Several mutations have been shown to cause the condition and the inheritance pattern varies between them. This variant is known to be inherited in an autosomal dominant fashion.
Myotonia congenita is a congenital muscular disorder as the name suggests that affects multiple breeds. The condition causes affected dogs to have hyperexcitable muscles that contract easily. The disorder is characterised by stiff movements and delayed muscle relaxation after exercise. The disorder is known to affect the Miniature Schnauzer, the Australian Cattle Dog and the Labrador Retriever. Myotonia congenita is inherited as an autosomal recessive trait.
Laxity of the hip joint is a frequent disorder in dogs. The disease is of multifactorial origin, which means that the symptoms are a combination of genetic factors as well as the environment.
Hip Laxity has two main characteristics:
• Laxity: This can be defined by ‘an abnormal freedom of movement of the bone in the hip joint’. As a result, the hip is less stable compared to healthy dogs.
• Ossification and bone formation. In younger dogs, the normal process of bone formation can be slowed down.
Both Laxity and Ossifcation disorders lead to the development of artrosis when dogs mature. Dogs which are affected most can already express symptoms after a few months. Other affected dogs develop artrosis at later ages.
This marker is part of a panel of genetic factors influencing hip laxity. The disease is of multifactorial origin, which means that the symptoms are a combination of genetic factors as well as the environment.
Hip dypslasia (HD)
In dogs, hip dysplasia is an abnormal formation of the hip socket that, in its more severe form, can eventually cause crippling lameness and painful arthritis of the joints.
It is important to note, that influences on the development and progression of hip dysplasia are concurrent with both genetic and environmental factors! The inheritance of HD is polygenetic, it means that we can't say for sure which gene causes it, thus we cannot test it, as a lot of factors can play a role in its development. Factors, like:
Genetic susceptibility for hip looseness or laxity
Rapid weight gain and obesity
In a normal hip joint, the head of the femur fits snugly into the joint socket, or acetabulum. In the dysplastic joint, the femoral head conforms poorly to the acetabulum. More space is evident between the bones. Displacement of the femoral head is the hallmark of the disease. Joints are evaluated using the FCI classification which is based on radiological features noted on a radiograph taken with the hind limbs extended of dogs between 1 and 2 years of age. It is as objective as possible. The FCI scoring mode:
A - no signs of hip dysplasia
B - near normal hip joints
C - mild hip dysplasia
D - mild hip dysplasia
E - moderate hip dysplasia
There are no cure for HD, so the only thing we can do is breeding selectively: taking out the affected dogs of breeding, and we do not breed with dogs whose relatives are also heavily affected with this deformation.
Elbow dysplasia (ED)
It is a condition caused by the abnormal growth of cells, tissue, or bone. The condition is characterized by a series of developmental abnormalities that lead to malformation and degeneration of the elbow joint. There are two main causes that could lead to ED:
Osteochondritis dissecans (OCD) is a type of inflammatory disorder that affects cartilage. When this happens, a dog's cartilage cells do not form properly, leading to unusually thick segments that break away from their connected bones
This theory is of joint incongruity as a primary cause of the fragmentation or resulting lack of fusion (ununited). Congruency is important in the elbow joint because three bones must fit together smoothly to allow for a gliding movement in flexion and extension as well as internal and external rotation.
The dog can be affected/free on only one or on both elbows. With surgery, the condition can be better, but the affected dogs are usually taken out of breeding.
Shoulder dysplasia/Osteochondritis dissecans (OCD)
Osteochondritis dissecans (OCD) is a type of inflammatory disorder that affects cartilage. With OCD, a dog's cartilage cells do not form properly, leading to unusually thick segments that break away from their connected bones. It can affect any joints, elbow, shoulder, knee, etc. This is developmental disease occurs in rapidly growing medium to large breed dogs typically between 6 and 9 months of age, and may occur more often in male dogs. This disease is more common in dogs receiving too much energy and calcium in the diet. Studies have shown that limiting dietary intake of energy and calcium reduces the incidence of this condition, and of other developmental orthopedic conditions.
In shoulder dyplasia cases, the prognosis improves if surgery is performed early in the course of the disease, before secondary degenerative joint disease occurs. Even though we don't know much about the genetic background of OCD, affected dogs are recommended to be taken out of breeding.