Cardiovascular

 

Cardiomyopathy

A blood disorder in which there is a deficiency of one of the factors needed for the normal coagulation of blood. Hemophilia 'A' is a sex-linked, recessive bleeding disorder affecting males caused by a deficiency of factor VIII, and Hemophilia 'B' or Christmas disease, in which there is a deficiency of clotting factor IX.

Refers to heart disease of the muscle (the myocardium) without malformation of the heart or its valves. Cardiomyopathy can also develop as a result of some toxins or infections.

  1. Dilated cardiomyopathy. This is by far the most common type in the dog. There is dilation of the chambers of the ventricles of the heart with some increase (hypertrophy) in the heart muscle mass, and a loss of the normal contracting abilities of the ventricles.
  2. Hypertrophic cardiomyopathy. In this form of cardiomyopathy, there is a tremendous increase in the mass of the heart muscle in the ventricles, with a resultant decrease in chamber size. Relatively few cases of hypertrophic cardiomyopathy in dogs have been reported, and no significant breed disposition has been identified. Most of the dogs affected have been male.

The heart works harder to compensate for the loss of contractility, eventually leading to congestive heart failure. The abnormalities in the heart muscle cells give rise to irregular heart rhythms which may cause sudden death.

 

Hepatic Lipidosis

An abnormal accumulation of lipids in the liver which leads to liver failure. Also known as "fatty liver disease", this disease is literally fat infiltration into the liver cells.

Mitral Valve Disease

The heart consists of four chambers -- 2 atria and 2 ventricles. The atrioventricular (AV) valves ensure that the blood flows from the atria to the ventricles when the heart beats. A defect in the mitral valve (the left atrioventricular valve) causes back flow of blood into the left atrium, or mitral regurgitation. Less commonly, a narrowing or stenosis of the valve can be identified. Because of the leaky valve, the heart is less efficient at pumping blood to the body. Mitral valve insufficiency is the most common acquired cardiac disease in older dogs, affecting over one third of dogs greater than ten years of age. In some breeds however, mitral insufficiency develops at a much younger age, due to an inherited predisposition for this disorder.

 

Patent Ductus Arteriosus "PDA"

Patent mean "open". The ductus arteriosus is a blood vessel connecting the main vessel leading to the lungs (pulmonary artery) to the main vessel of the body (aorta). PDA is the failure of the vessel remnant joining the aorta and pulmonary artery in fetal life to close properly at birth. This is too much blood into the lung and fluid in the lung increases, making it difficult to breathe. The PDA increases the work of the heart, and may develop heart failure if the amount of blood flowing through the PDA is too large. 

Portosystemic Shunt

In animals with a portosystemic shunt (PSS) there is abnormal blood flow in the liver.  Blood should flow from the digestive tract to the liver via the portal system into the blood vessels of the liver, and then to the caudal vena cava which is the large blood vessel carrying blood back to the heart. In a portosystemic shunt, as the name implies, portal blood by-passes the liver and goes directly to the systemic venous circulation (caudal vena cava). One important function of the liver is to clear toxins, many of which are by-products of protein digestion,  from the blood. In PSS, these toxins are not cleared, and circulate in the body. This causes the clinical signs associated with PSS, many of which are neurological. The complex of neurological and behavioral signs caused by liver dysfunction is called hepatic encephalopathy.

Portosystemic shunts may be acquired secondary to another disease, or they may be congenital - that is the animal is born with a shunt. A congenital shunt usually occurs as a single abnormal blood vessel that is a remnant of normal embryonic development. These shunts are defined as intra-hepatic or extra-hepatic depending on the location of the blood vessel in relation to the liver.

Most animals with congenital portosystemic shunts show clinical signs before 6 months of age. Where signs are subtle, the condition may not be diagnosed until much later. 

 

Pulmonic Stenosis

As part of normal circulation in the body, the right side of the heart (the right ventricle) pumps blood to the lungs to receive oxygen. The oxygenated blood goes back to the left side of the heart from which it is pumped out to the rest of the body.

Blood flows from the right ventricle of the heart through the pulmonic valve into the pulmonary artery and thence to the lungs. With pulmonic stenosis, there is partial obstruction of normal blood flow, most commonly due to a malformation of the pulmonic valve ("pulmonic valve dysplasia") but the abnormality may be immediately above or below the valve as well.

The effect of this partial obstruction is to force the heart to work harder to pump blood to the lungs. The extent to which a dog will be affected depends on the degree of narrowing (stenosis) of the valve area. With severe stenosis the dog will likely develop congestive heart failure due to the increased workload of the heart.

Sick Sinus Syndrome

Sick sinus syndrome is a disturbance of the normal rhythm of the heart. The electrical impulse that drives the heart beat starts in the sinoatrial (SA) node of the heart, and then spreads through specialized conduction pathways, causing orderly depolarization and contraction of the heart muscle. This can be traced on an electrocardiogram.

Sick sinus syndrome is the name given to a number of arrhythmias (irregular rhythms) that arise because of abnormal function of the SA node. Clinically, the arrhythmias may cause weakness and fainting.

Ventricular Septal Defect (VSD)

A ventricular septal defect is a hole (or defect) in the muscular wall of the heart (the septum) that separates the right and left ventricles.

Before birth, the heart starts out as a single tube which gradually differentiates into 4 chambers during embryological development.  Abnormalities can arise at several steps in the process, resulting in defects in the muscular walls that normally separate the heart into the right and left atria, and the right and left ventricles. The result is abnormal blood flow in the heart with varying effects in the dog, depending on the size and location of the defect.

 

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"Just because some people select and breed dogs now does not mean that the original dogs were created that way. Looking closely at the behavior of wolves, and understanding the biology of a wild animal, I don't think there is a ghost of a chance that people tamed and trained wild wolves and turned them into dogs. I think a population (at least one) of wolves domesticated themselves."

-Raymond Coppinger

 


 

Common breeding tests for the Shetland sheepdog include eye tests, hips/elbows/knees, thyroid panels and sometimes vWD certification.

The only breeding test that can 100% identify whether or not your puppy has any one of the genetic diseases listed above is the vWD-DNA test. However, this disease is very rare in shelties, affecting 1% of the breed's population.

 

Eye exams

Eye exams certified by the Canine Eye Registration Foundation (CERF), which reports any eye abnormalities in the breed due to hereditary disease. In Shetland sheepdogs, the two main concerns are Collie Eye Anomaly (CEA) and Progressive Retinal Atrophy (PRA).

 

Hips/Elbows/Knees

This is done through x-rays evaluated by three specialists at the Orthopedic Foundation for Animals (OFA) or PennHip (University of Pennsylvania) and is used to detect the presence of hip dysplasia. OFA will do preliminary evaluations on dogs under two years of age, but will only certify dogs over two years of age. Dogs that have preliminary certification done through OFA, should have x-rays resubmitted because they are not given a permanent rating and often times, the rating can change for better or worse.

 

Thyroid

This test is used to detect autoimmune thyroid disease. Autoimmune thyroiditis can be influenced by environmental changes, such as excessive heat; or hormonal changes, such as aging. A thyroid test is a blood test and should be a complete panel that includes Total T4, Free T4, Total T3, Free T3, T4 auto antibodies, T3 auto antibodies, TSH (thyroid stimulating hormone), and TgAA. A thyroid test is not always a conclusive diagnosis.

 

vonWillebrand's Disease

vWD, Factor III is a bleeding disorder in the Shetland sheepdog. The DNA test determines whether a dog is affected (two genes), a carrier (one gene), or clear of the disease. According to vetGen, affected shelties are very rare: (7% carrier-status; 1% affecteds as of January 26, 2005). Most breeders will not introduce the affected gene, but those that are breeding affected lines can easily & effectively manage its safe elimination through prudent vWD-DNA testing.

 

Control of Canine
Genetic Diseases
by George A. Padgett, DVM
ISBN 0-87605-004-6

Genetics of the Dog
by Malcolm B. Willis
ISBN 0-87605-551-X

Dog Owner's
Home Veterinary Handbook
by James M. Giffin, MD &
Liisa D. Carlson, DVM
ISBN 0-87605-201-4

Medical &
Genetic Aspects of
Purebred Dogs
Edited by Ross D. Clark, DVM &
Joan R. Stainer
ISBN 0-935078-24-X

Canine Inherited
Disorders Database (CIDD)
http://www.upei.ca/cidd/

Alice Crook, BSc, DVM
Brian Hill, DVM, MS, DACVIM
Sue Dawson, BA, PhD


Amatras are breeders dedicated to focusing on longevity, health, temperament, structure, brains and beauty. Dogs are added to the program with these qualities only and bred only to improve each trait through each successive generation.

 

 

 

© Amatras Shetland Sheepdogs

Englewood, Florida

Established 2000.