Scottish Terrier Genetic Issues
Any purebred or mixed-breed dog can inherit mutated gene(s) from one or both parents that may predispose him to a particular disease. Scotties are fortunate to have relatively few serious genetic problems, and responsible breeders work hard to minimize these problems in their breeding stock. The following genetic disorders have been reported in Scotties.
VonWillebrand’s Disease (vWD)
This serious blood clotting disorder was previously recognized in the Scottie but today is not often seen thanks to the widespread use of a simple DNA test to identify the mutation. Used by all reputable breeders before producing their litters, this cheek swab test identifies the Affected individual (having both copies of the mutated gene), the Carrier individual (having one copy of the mutated gene and one normal copy but not showing signs of the disease), and the Clear individual (having two normal copies of the genes). Affected dogs are removed from the breeding program, and the carrier dogs are monitored closely and eventually retired. This strategy has resulted in the near elimination of the disease in litters today. If you are looking for a Scottie pup, always ask the breeder for evidence that parents are free of the vWD mutation.
Scottie Cramp is not actually a muscle “cramping” disorder, nor is it a seizure. Cramp is a genetic dysfunction of the chemical neurotransmitter made by the nerves that control the dog’s muscles. Affected Scotties are normal at rest and exhibit normal ability to walk until they become stressed. After several minutes of strenuous activity and/or excitement, an affected dog may arch its back, walk stiffly, become immobilized, and may even roll to its side. A short while after the stimulation abates, the dog will recover and appear completely normal. Scottie Cramp is a non-painful, episodic disorder, not constantly present; nor does it compromise the dog’s quality or length of life. Many affected dogs learn to manage the problem on their own and will stop running before symptoms appear. Sometimes an affected dog that is only leash-walked or that never has the opportunity to run strenuously will fail to exhibit clear symptoms at all. As of 2018, the mutation causing Scottie Cramp has not yet been identified, so there is no current DNA test available. The incidence of Scottie Cramp has dramatically decreased in litters where the breeders carefully research and avoid the pedigrees with a history of this disorder.
Cerebellar Abiotrophy (CA)
CA is an uncommon neurologic disorder caused by a genetic mutation leading to gradual death of the Purkinje cells in the cerebellum of the brain. Scotties with CA are born without symptoms of this disorder, but after a few months or even years in some cases, they begin to develop a wobbly gait, incoordination, and the inability to run smoothly or to navigate stairs. CA is not a painful disease, nor does it cause weakness or affect the mental abilities of the dog. But CA is ever-present, and it usually progresses over the life of the dog. CA does affect the quality but not necessarily the length of life. Although a genetically-based test is not yet available as of 2018, conscientious breeders screen potential parents for any history of CA in their lineage and consult the STCA’s database of affected dogs.
Craniomandibular Osteopathy (CMO)
Thankfully rare in the Scottie, CMO is a genetic disease of the bones of the jaw, typically seen in the 4-7-month-old pup. The disorder causes over-growth and painful swelling in the lower jaw. The puppy may be feverish, reluctant to open the mouth or to eat. A diagnosis of CMO is confirmed by a veterinarian using x-ray. This disorder is transient and can be successfully treated with appropriate medication. There is a DNA test now available as of 2018 to identify the Affected, Carrier and Clear individuals. With this tool, breeders are able to avoid this disease entirely in their programs.
Liver Shunt (Portosystemic Shunts)
Liver shunts can arise in any purebred or mixed breed dog. They go by many different names, but the underlying issue is a mutation or mutations that lead to the development of abnormal shunting of blood flow either around or through the liver, thereby decreasing the delivery of nutrient rich components essential for normal growth and function of the liver cells. Liver shunts have been reported in a few Scotties, and this disorder continues to appear occasionally in certain lines. Most of what is known about liver shunts in dogs comes from research done on Yorkshire Terriers, a breed where this problem is widespread due to the repeated use of shunt producers and carriers over many generations. And yet, despite years of painstaking research, the mutation(s) involved in this disorder and the mode of inheritance have not been identified as of 2018.
Liver shunts can be detected early in puppies or they can emerge later in life in the adult dog. Puppies born with a liver shunt are typically small and unthrifty. They often exhibit bizarre, neurological behavior, especially after eating, due to the build-up of nitrogenous wastes in the blood. Diagnosis is made by a bile acid test which assesses the function of the liver. Follow-up ultrasound examination will reveal the abnormal shunting of blood flow and confirm the location and type of shunt. Surgery may correct the condition depending on the location of the shunt or shunts, but this procedure requires great skill and is very expensive. As it is not possible to predict which dog will produce an affected puppy or which dog will carry the genetic mutations that will be passed along to the next generations, geneticists recommend that dogs who produce liver shunts should not be bred again, and the siblings of an affected dog should also be spayed/neutered.