HEREDITARY DISEASES DEAFNESS INSIDE THE DOGS EAR WHAT CAUSES DEAFNESS

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1 HEREDITARY DISEASES There are 5 known hereditary diseases in bull teriers (Deafness, Heart Disease,Polycystic Kidney Disease, Nephritis Kidney Disease, Patella Luxation (unusual movement of the patella (knee Cap) ) and Lens (Eye) Luxation in Miniature Bull Terriers DEAFNESS Bull Terriers along will other breeds carry the deafness gene It can affect both coloured and white Bull Terriers. Dogs can be totally deaf (Bilateral deafness )or can have hearing in one ear ( Unitaleral deafness) INSIDE THE DOGS EAR Their are four parts to a dogs ear, the ear flap, the ear canal, the middle ear and the inner ear. The ear flap is made of cartilage, muscle and skin which you can see on the dogs head this flap captures sound waves and allows them to travel to the ear drum (tympana membrane) which than vibrates. The middle ear is the area behind the ear drum which contains the tympana cavity. This is where the auditory tube, the tympana nerve, the vestibulal window and the cochlea along with other parts are. Also within the middle ear are three small bones ( the smallest bone in the body) the malleus. The incus and the stapes. These bones transmit the air vibrations from the ear drum and tympanic cavity to the inner ear. The inner ear is where the air vibations are converted into nerve impulses, which when reaching the brain results in hearing. It is a labyrinth of fluid filled sacs, which are contained within an osseous lebyrinth. The osseous parts of the inner ear are a shell shaped cochlea. This cochlea winds around a hollow core,containing the cochlea nerve. Within the cochlea are around 10,000hair cells which respond to the air vibrations and stimulates the nerve cells to send messages to the brain, these hair cells are what the ear uses to changes to electrical signals that the brain then recognises as sound. WHAT CAUSES DEAFNESS The cause of deafness is not yet fully understood, however it is believed to be caused by the loss of blood supply to the cochlea and thus causing the degeneration of the hair cells contained in the cochlea. Without these hair cells their is no way the ear can change air vibrations into electrical signals which the brain recognises as sound. Inheritance is not known at this time though DNA testing is being conducted to try and find the gene which produces deafness, as two fully hearing parents can produce deaf or partial deaf puppies while in the same litter you can have full hearing puppies.

2 BAER TESTING BAER (Brainstem Auditory Evoked Response) The only way to be certain that you dog can hear properly from both ears. In this test a computer is used to record the electrical activity of the brains response to sound stimulation. A sound stimuli, a series of clicks, is passed though headphones placed over the dogs ears whilst recording electrodes are placed on the dogs neck just behind the head. Puppies can be tested from 6 weeks of age and will require a light sedation to keep them still. BAER testing is required only one in a puppies life and a certificate will show the results. Image 1: BAER Testing

3 KIDNEY DISEASE POLYCYSTIC KIDNEY DISEASE AND HEREDITARY NEPHRITIS WHAT THE KIDNEYS DO The Kidneys primary function is to regulate the plasma and tissue fluid in the body by the formation of urine, quite simply the kidneys are filtering harmful toxins from the body though the urine. In the process of urine formation the kidneys also regulate: 1. The volume of blood plasma and thus significantly to the regulation of blood pressure, 2. The concentration of waste products in the blood, 3. The concentration of electrolytes and other ions in the plasma and 4. The ph of plasma So if the kidneys do not work correctly it can have a devastating effect on the whole body. WHAT IS POLYCYSTIC KIDNEY DISEASE Polycystic kidney disease (PKD) is an inherited disease characterized by the growth of numerous cysts filled with fluid in the kidneys. PKD cysts can slowly replace much of the mass of kidneys, reducing kidney function and leading to kidney failure.there is no cure for Polycystic kidney disease some diets may slow down the speed of the kidney degeneration however the final result is death from kidney failure. MODE OF INHERITANCE Polycystic kidney disease is a autosomal dominant hereditary disease, which means that one or both of the parents have the gene and will pass it on to up to 90% of the litter.the disorder can be readily eliminated by avoiding the breeding of affected individuals. TESTING FOR POLYCYSTIC KIDNEY DISEASE Testing for Polycystic kidney disease is by renal ultrasound, which demonstrates the presence of fluid -filled cysts in the cortices and medullae of the kidney

4 WHAT IS HEREDITARY NEPHRITIS: Hereditary Nephritis is inherited in an autosomal dominant manner and is characterised by glomerulopathy, progressive renal atrophy and renal failure at varying ages. MODE OF INHERITANCE. Hereditary Nephritis is an autosomal hereditary disease which may be inherited from either parent, is reqiured to produce the trait. The parent with the dominant trait will pass the affected gene to approximately half the offspring, and the trait will be apparent in both the parent and the affected progeny. The disorder can be readily eliminated by avoiding the breeding of affected individuals. TESTING FOR HEREDITARY NEPHRITIS: Testing is by the collection of a midstream urine sample ( the first of the day ) in a sterile pot and sent to the lab for Protein:creatinine ratio analysis. The UPC will be returned within 24 hours and should be 0.3 or under. UPC of over 0.3 does not mean the dog has hereditary Nephritis and tests should be preformed to rule out renal tract infection. IN BOTH POLYCYSTIC KIDNEY AND HEREDITARY NEPHRITIS IT IS IMPORTANT TO TEST BOTH DOGS AND BITCHES AFTER THE AGE OF 1 YEAR

5 THE PATELLA AND WHAT IT DOES: PATELLA LUXATION The canine patella is equivalent to the human knee cap. It is a bony structure that sits in a groove in the femur (thigh bone) on the front of the stifle (Knee Joint) Attached to the patella is the Quadriceps tendon and the patellar tendon. The quadriceps tendon runs from the patella up to the muscle mass on the front of the thigh and to a lesser extent down over the patella tendon. The patella tendon runs from the patella down to a protuberance on the front of the tibia. When the muscles contract, they pull the quadriceps tendon up which pulls the patella up, which, in turn pulls on the tibia via the patella tendon. The result of all this pulling is to straighten or extend the leg. As the leg is extended and flexed, the patella rides up and down in the trochlear groove. Ideally, the groove should be deep enough for the patella to fit snugly into it. If the tendons, muscles and bones are all aligned properly, the result is a stable, sound stifle joint. Improper alignment means instability and this not only leads to degenerative joint disease, but also places increased stress on other ligaments and supporting structures. PATELLAR LUXATION: The patella luxates because the point of attachment of the patellar ligament is not on the midline of the tibia. It is almost always located too far medial (toward the middle of the body). As the thigh muscles contract, the force is pulled against the groove on the inner side of the femur. After several months or years of this abnormal movement, the inner side of the groove wears down and the patella is free to move out of the groove or dislocate. When this occurs, the dog has difficulty bearing weight on the leg. It may learn how to kick the leg and snap the patella back into its normal location. However, because the side of the groove is gone it dislocates again easily..grade 1: The stifle joint is almost normal and the patella luxates only when the leg is extended and the patella is pushed.when the leg is extended, there is less tension on the tendons holding the patella in place, and it is thereforeeasier to push out of place. Usually, there is no gait abnormality, but as the animal becomes older, it maydevelop arthritis. Grade 2:The patella usually lies loosely in its normal position, but it will luxate medially with flexion of the joint. These animals have a "hopping" gait. The patella becomes trapped out of the trochlear groove on flexion and the dog hops along on the other leg while kicking the sore leg straight to allow the patella to move back into position. Animals with Grade 2 luxation are more likely to develop arthritis that thosewith Grade 1 because of the greater degree of abnormal patella movement.

6 Grade 3:The patella is dislocated most of the time, but can be put back manually of the leg is extended. Grade 4:The patella is dislocated all of the time and cannot be corrected without surgical intervention. Grades 3 and 4 show varying degrees of lameness, often the dog assumes a crouched position due to the inability to fully extend the stifles; often they appear bowlegged with the toes pointed inwards due to the deformities in the rear limbs. THE LUXATING PATELLA CAN BE CORRECTED. The methods used for surgical repairs depend on how far the process has gone before intervention.surgical repairs may include any or all of the following: 1) The point of attachment of the patellar ligament is cut from the tibia and transplanted to its proper location to correct the in correct alignment. 2) The groove in the femur is deepened so the patella will stay in place. 3) The capsule around the joint is tightened. The last step is important because the joint capsule will have stretched during the period of luxation. If surgery is performed before arthritis occurs, the prognosis is excellent. The dog will regain full use of its legs However if arthritis has already occured, the joint will still be somewhat painful, especially in cold weather. BREEDING WITH DOG WITH LUXATING PATELLA. Because of the strong genetic relationships, animals with this disorder should not be used for breeding. They can still be excellent pets and those that do require surgery will usually lead perfectly normal lives without any restrictions on activity.

7 Image 2: Patellas

8 HEART DISEASE WHAT IS CONGENITAL HEART DISEASE? A heart condition due to structural defect within the heart present at birth. Cardiac defects in Bull terriers include leaky valves or narrowed valves. Both of these general defects will result in a heart murmur - an abnormal heart sound which is detected with a stethoscope by a veterinary cardiologist or a veterinary surgeon. OVERALL VIEW OF THE NORMAL ANATOMY OF THE HEART: The heart has four chambers. The right atrium (RA) collects venous blood from the body, and it passes through the tricuspid valve to the right ventricle (RV) The right ventricle pumps the venous blood, though the pulmonic valve, into the pulmonary artery and so into the lungs, where the blood is oxygenated. The blood returns to the heart, into the left atrium(la) Blood passes though the open mitral valve into the main pumping chamber of the heart, the left ventricle (LV) When this pumps, the mitral valve closes and blood is ejected out via the open aortic valve into the aorta which divides to every artery to all the organs of the body. MITRAL DYSPLASIA: Mitral dysplasia is a malformation of the mitral valve apparatus. The normal mitral valve apparatus consists of two valve cusps. These are anchored by chordae tendinae to two papillary muscles in the left ventricle. The papillary muscles and the cow the valve to close when the ventricle contracts, but restrain the valve so it does not flap back into the left atrium. The closed valve should be a tight seal, allowing no blood into the left atrium.with mitral Dysplasia in Bull Terriers, the mitral valve apparatus is deformed. The valve cusps become thickened and nodular. The papillary muscles are very large and thick and only very short, thickened and chordae tendinae attach the papillary muscles to the valve leaflets.the most common consequence of mitral dysplasia is a leaky mitral valve. During ventricular contraction (systole) instead of the mitral valve sealing shut it allows a jet of blood to pass backwards into the left atrium, as well as pumping blood forward in the normal direction, into the aorta. This leak is known as mitral regurgitation The turbulent jet of blood flow due to mitral regurgitation can be heard with a stethoscope it is a systolic heart murmur, which is most intense over the mitral valve area of the dogs chest. Loud murmurs can radiate to other parts of the dogs chest as well.occasionally, the mitral valve in mitral dysplasia can be narrowed as well, called mitral stenosis. It is difficult for the left atrium to empty into the left ventricle. Pressures can build up in the left atrium. The left atrium may become greatly enlarged.

9 CONSEQUENCES OF MITRAL DYSPLASIA: Dogs with mitral dysplasia will have a heart murmur. If the valve is only slightly leaky, the murmur is only soft and the dog may not be affected at all. Where there is severe mitral regurgitation, a large volume of blood moves back and forwards across the mitral valve, overloading the left side of the heart. The left atrium and left ventricle can became very large indeed. Changes occur gradually, but eventually, pressures build up in the left atrium, and blood dams back into the lungs, and comes out of the circulation into the normally air filled spaces of the lungs - this is called pulmonary oedema. Once this happens, the dog is in congestive heart failure. Dogs with pulmonary oedema will be breathless and will cough. With mitral stenosis also present, left atrial enlargement in massive and pulmonary oedema rapidly develops. Where the left atrium becomes very stretched, irregular or chaotic heart rhythms can develop, such as atrial fibrillation. The rhythm will worsen the symptoms of dogs with congestive heart failure, especially if they have mitral stenosis.dogs with severe mitral dysplasia have poor heart output into their circulation they may faint on exertion or excitement or stress (syncope) as their brains can become short of oxygen. AORTIC STENOSIS The aortic valve is positioned between the left ventricle and the aorta. It opens as the left ventricle contracts, allowing the left ventricle to eject blood into the aorta. It normally offers no restriction to blood flow.with aortic stenosis, the aortic valve itself or a fibrous band beneath the valve (Subaortic stenosis) restricts the outflow to blood from the left ventricle. The left ventricle has to work hard just to eject blood, and the heart muscle becomes thickened to compensate. Blood ejecting past the obstruction to outflow is very fast and turbulent. This turbulent flow causes a heart murmur which can be detected with a stethoscope over the aortic valve area of the chest wall. The louder the murmur, the more severe the aortic stenosis and the faster and more turbulent the blood flow passing the obstruction. This turbulent blood flow can affect the walls of the aorta, and it can stretch, called post-stenotic dilation. As the left ventricle muscle thickens, it exceeds the coronary artery blood supply to it. This means that areas of the heart can be deprived of oxygen. The muscle becomes irritable and may cause abnormal beats (called ventricular premature complexes or VPCs) DIAGNOSIS OF CONGENITAL HEART DISEASE As explained above, congenital heart disease is manifested by a heart murmur, which is detected by a veterinary surgeon or a veterinary cardiologist by careful clinical examination, including auscultation, with a stethoscope. Because Bull Terriers are not easy dogs to auscultate, sometimes the dogs own veterinary surgeon may not have detected the murmur.

10 Heart murmurs show that there is turbulent blood flow in the heart, which is abnormal. Murmurs are graded out of 6 - where Grade 6 is the loudest murmur which can be detected. Grade 1 murmurs are the most quiet and difficult to detect. A very quiet room, a good quality stethoscope and a quiet, calm dog who is not panting are required before the murmur is detected. MODE OF INHERITANCE This is not yet been proven, However the fact it is common in Bull Terriers and in certain family lines, there is significant clustering of heart disease, it probably is inherited. Careful family history, cardiac examinations is necessary before breeding and any animals found with heart murmurs of any grade should be removed from a breeding programme. CONCLUSION It is a devastating thing to watch a young Bull Terrier, who should be in the prime of life, slowly die with heart failure or even drop dead suddenly. Testing all breeding stock before breeding is the only way we can protect Bull Terriers in the future from being born with heart disease. Image 3: Inside heart