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*Definitions (with an asterisk) provided by the (Alice Crook, Author) |
What is brachycephalic syndrome? The full name of this disorder is brachycephalic airway obstruction syndrome (BAOS). Brachycephalics are those breeds which have a comparatively short head. Because of their anatomy, virtually all dogs of these breeds have some degree of increased work associated with breathing from the time they are born. Many have varying degrees of obstruction to their airways, which causes signs ranging from noisy breathing to collapse. The most common anatomical features that lead to the respiratory difficulties typical of these breeds, include an elongated and fleshy soft palate, and narrowed nostrils. Many affected dogs also have changes to the larynx (everted laryngeal saccules) and a relatively small trachea (hypoplastic trachea). How is brachycephalic syndrome inherited? Selection for exaggerated features has resulted in the respiratory difficulties in these breeds. For example breed standards for the English bulldog specify that the face should be very short, as should the distance between the tip of the nose and where it is set deep between the eyes. It is hardly surprising that this leaves little room for the structures involved in normal breathing. What breeds are affected by brachycephalic syndrome? These problems are generally most common and severe in the English bulldog. Other brachycephalic breeds in which this syndrome is found include the pug, Boston terrier, Pekingese, Cavalier King Charles spaniel, Chinese shar-pei, French bulldog, Lhasa apso, and shih tzu. For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed. What does brachycephalic syndrome mean to your dog & you? Problems associated with this syndrome range in severity, with most brachycephalic dogs snuffling and snorting to some degree. Some will have no further difficulties, but many will have problems such as increasingly noisy breathing, coughing and gagging, fainting or collapsing episodes, and a decreased tolerance for exercise (ie. they tire easily). Over the long term, this also puts an increased strain on the heart. Some dogs, such as English bulldogs, may have frequent episodes of sleep-disordered breathing. Overheating is especially dangerous in these breeds, because increased panting (the normal mechanism for cooling in dogs) can cause further swelling and narrowing of the already constricted airways, which will increase your dog's anxiety. Excitement, exercise, or warm weather (and especially a combination of these factors) can trigger this vicious cycle. These dogs can also have gastrointestinal problems, because of difficulties coordinating swallowing when they are working so hard at breathing. This can result in vomiting ar gagging because of swallowing so much air, or aspiration pneumonia, because of breathing in saliva or food particles. All dogs of these breeds have an increased risk associated with sedation and anesthesia, for which your veterinarian will take extra precautions. How is brachycephalic syndrome diagnosed? These problems are usually evident from a young age. If your dog has respiratory difficulties, your veterinarian may discuss this syndrome with you as part of a regular visit, or you may bring your dog in because of an episode such as collapsing after exercise. Because some changes in anatomy are common to all dogs of these breeds, diagnosis is really a question of the degree of abnormality. The overlong soft palate is best examined under general anesthesia, and so, because of the associated risks, your vet will most likely ask your permission in advance to surgically correct it at the same time if necessary. Neutering can often be performed at the same time. How is brachycephalic syndrome treated? Medical treatment (oxygen therapy, corticosteroids) can be used for short term relief of airway inflammation. Surgery is required where severe anatomic faults interfere with breathing. Most commonly this involves removal of some of the excess fleshy soft palate, and widening of air passages at the nostrils. It is important to keep your dog from becoming overweight, as this will worsen his or her respiratory difficulties in the long run. For the veterinarian: In mild episodes of obstruction, short-acting steroids, oxygen therapy, and cooling the dog while it calms down may be sufficient. Bear in mind that sedation without intubation will relax upper airway muscles and may increase obstruction, and that hyperthermia may develop in an oygen tent or cage and exacerbate the problem. These dogs, particularly the English bulldog, have an increased risk of aspiration pneumonia following surgery to correct airway problems. FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN. Resources Hendricks, JC. 1995. Recognition and treatment of congenital respiratory tract defects in brachycephalics. In JD Bonagura and RW Kirk (eds.) Kirk's Current Veterinary Therapy XII Small Animal Practice.p. 892-894. W.B. Saunders Co., Toronto. Copyright © 1998 Canine Inherited Disorders Database. All rights reserved. Revised: December 07, 2001. This database is a joint initiative of the Sir James Dunn Animal Welfare Centre at the Atlantic Veterinary College, University of Prince Edward Island, and the Canadian Veterinary Medical Association. |
related terms: dry eye What is keratoconjunctivitis sicca (KCS)? KCS or "dryeye" is an eye disease caused by abnormal tear production. The lacrimal glands produce the watery secretions that make up the bulk of the tears. A deficiency in this secretion causes KCS in small animals. Normal tears are essential for the health and transparency of the cornea (the surface of the eye). Tears cleanse and lubricate the cornea, carry nutrients, and play a role in the control of infection and in healing. Deficient tear production as in KCS causes chronic irritation of the cornea and conjunctiva. Corneal ulcers and eventually corneal scarring occur, and blindness can result. There is a predisposition to this condition in some breeds as listed below. KCS can also occur in any breed as a result of viral infection, inflammation, drug-related toxicity, or immune-mediated disease. There is an association between removal of a prolapsed nictitans gland ("cherry eye") and the development of KCS. How is KCS inherited? The mode of inheritance is not known. What breeds are affected by KCS? There is a predisposition to the development of KCS in the bloodhound, Boston terrier, bull terrier, English bulldog, English and American cocker spaniel, Kerry blue terrier, Lhasa apso, miniature poodle, miniature schnauzer, Pekingese, pug, Sealyham terrier, Shih tzu, standard schnauzer, West Highland white terrier, Yorkshire terrier Congenital KCS (ie. the dog is born with the condition) is rare. It may be one-sided and has been seen in toy breeds such as the Yorkshire terrier, pug, Pekingese, and Chihuahua. These dogs have very small or absent tear-producing (lacrimal) glands. For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed. What does KCS mean to your dog & you? KCS may develop very quickly or more slowly, in one or both eyes. Commonly it is diagnosed in 1 eye first and develops in the other eye within several months. The extent of discomfort depends on the severity of the tear deficiency and how long it has been present. People with KCS say it feels like they have sand paper under their eyelids with every blink. Dogs show their discomfort by rubbing their eyes, squinting, and being sensitive to light. Your dog's eye(s) may be reddened and inflamed, or the cornea may appear dull and dry. There is commonly a thick mucousy discharge in the eye or in the area around the eye. Problems associated with KCS include chronic or recurring irritation or infection of the conjunctiva and cornea, and corneal ulcers. These conditions are painful and, if KCS is untreated, over the long term the normally transparent cornea becomes thickened and scarred. Blood vessels and pigmented cells move in to the cornea because of the chronic inflammation, and blindness may result. How is KCS diagnosed? Your veterinarian may suspect KCS based on the kinds of clinical signs mentioned above, particularly in a breed with a predisposition to this disorder. KCS is confirmed by measuring your dog's tear production. Your veterinarian will also perform a fluoroscein dye test to check for corneal ulceration. FOR THE VETERINARIAN: A Schirmer tear test (STT) should be performed before the use of any drops or ointments in any dog presenting with ocular discharge, irritation, or corneal lesions. Normal STT values in the dog are 15 to 25 mm/minute. Dogs with exposed corneas due to conformation require relatively more tears so may show KCS even with marginal deficiencies. How is KCS treated? The goals of treatment are to restore moisture to the eye and to treat conditions such as infection or ulceration that develop because of the lack of normal tears. Tear stimulants and artificial tear replacements are used to treat KCS. Generally it will take a period of trial-and-error for your veterinarian to determine what is best for your dog. A response to tear stimulants may not occur for a few weeks or even longer, and during this time artificial tears must be used as well. Once tear production has been established, often the use of a tear stimulant once daily, or sometimes once every 2 days, will be sufficient to control KCS. It is important to recognize that this treatment is not a cure for KCS but rather a way to manage a frustrating, painful, and potentially blinding condition. Clinical signs will slowly return If treatment is stopped. When medical therapy as outlined above is unsuccessful, surgery can be done to transport one of the salivary ducts to provide moisture to the eye. This is generally less satisfactory. FOR THE VETERINARIAN: Cyclosporine is the treatment of choice due to its efficiency at stimulating tear production, the need for fewer applications, and the lack of undesirable side effects with long term use. The time required to achieve sufficient tear production varies; usually a response is seen within a few weeks but several weeks may be required. Artificial tears should be supplied until tear production is established. FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN. Where to find more information? Salisbury, M.A. 1995. Keratoconjuctivitis sicca. In J.D. Bonagura and R.W. Kirk (eds.) Kirk's Current Veterinary Therapy XII Small Animal Practice. p. 1231-1239. W.B. Saunders Co., Toronto. Copyright © 1998 Canine Inherited Disorders Database. All rights reserved. Revised: April 11, 2000. |
What is retinal dysplasia? The normal retina lines the back of the eye. The retinal cells receive light stimuli from the external environment and transmit the information to the brain where it is interpreted to become vision. In retinal dysplasia, there is abnormal development of the retina, present at birth. The disorder can be inherited, or it can be acquired as a result of a viral infection or some other event before the pups were born. There are 3 forms of retinal dysplasia i) folding of 1 or more area(s) of the retina. This is the mildest form, and the significance to the dog's vision is unknown. ii) geographic - areas of thinning, folding and disorganization of the retina. iii) detached - severe disorganization associated with separation (detachment) of the retina. The geographic and detached forms cause some degree of visual impairment, or blindness. How is retinal dysplasia inherited? In many breeds, inheritance has been shown or is suspected to be autosomal recessive. In others, the mode of inheritance has not been determined. What breeds are affected by retinal dysplasia? Breeds most commonly affected with the detached or geographic form of this condition include the American cocker spaniel, Bedlington terrier, English springer spaniel, golden retriever, Labrador retriever, Sealyham terrier, and Yorkshire terrier. Retinal dysplasia has been seen in many other breeds as well, including the akita (folds,geographic/detachment), Australian shepherd (folds), beagle (folds), Belgian malinois (folds), border terrier (folds), bull mastiff (folds), Cairn terrier (multifocal folds, geographic), cavalier King Charles spaniel (folds and geographic/detached), clumber spaniel (folds), collie (folds), field spaniel (folds), German shepherd (folds), Gordon setter (folds), mastiff (folds), Norwegian elkhound (folds), old English sheepdog (folds), Pembroke Welsh corgi (folds and geographic/detached), rottweiler (folds), samoyed (folds,geographic/detached), soft-coated wheaten terrier (folds), Sussex spaniel (folds). Labrador retrievers and samoyeds with retinal dysplasia may also have a bony abnormality called chondrodysplasia, or dwarfism. The dog's front legs are shorter and thicker than normal. For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed. What does retinal dysplasia mean to your dog & you? The effect on vision of the mildest form (folding of the retina) is not known. The abnormal retinal folds may disappear with age in dogs that are only mildly affected. There is some loss of vision or blindness with the geographic or detached forms of retinal dysplasia, and this is present for the dog's whole life. With their acute senses of smell and hearing, dogs can compensate very well for visual difficulties, particularly in familiar surroundings. In fact owners may be unaware of the extent of vision loss. You can help your visually impaired dog by developing regular routes for exercise, maintaining your dog's surroundings as constant as possible, introducing any necessary changes gradually, and being patient with your dog. How is retinal dysplasia diagnosed? The condition is present from birth. At 3 to 4 weeks of age, the breeder may notice that severely affected pups are less active and frequently bump into objects. A veterinarian will be best able to examine the pup's eyes for this condition with an ophthalmoscope at 12 to 16 weeks of age, when the retina is mature. In less severely affected pups, or those with retinal folds only, no behavioural abnormalities are likely to be seen. Your veterinarian may find this condition during an eye exam and/or you may begin to suspect there is a problem with your dog's sight. For the veterinarian: Ophthalmic exam - There may be a searching nystagmus due to the lack of normal development of neural visual pathways. PLR may be absent. The anterior segment is clinically normal. You may see multiple gray or white spots or streaks (multifocal retinal folds) or retinal detachment, with or without intraocular haemorrhage. The retina often remains attached at the optic disk. Inherited retinal dysplasia can not be distinguished by ophthalmic exam from the acquired form. How is retinal dysplasia treated? There is no treatment for retinal dysplasia. With their acute senses of smell and hearing, dogs can compensate very well for visual difficulties, particularly in familiar surroundings. In fact owners may be unaware of the extent of vision loss. You can help your visually impaired dog by developing regular routes for exercise, maintaining your dog's surroundings as constant as possible, introducing any necessary changes gradually, and being patient with your dog. FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN. Resources Ackerman, L. 1999. The Genetic Connection. p. 168-171. AAHA Press. Lakewood, Colorado. This reference contains a comprehensive list of breeds with whom this disease has been associated. Copyright © 1998 Canine Inherited Disorders Database. All rights reserved. Revised: September 20, 2004. This database is funded jointly by the Animal Welfare Unit at the Atlantic Veterinary College, University of Prince Edward Island, and the Canadian Veterinary Medical Association. |
What is deafness? Inherited deafness in one or both ears occurs due to the degeneration of sensory inner ear structures (sensorineural deafness) within a few weeks of birth. This occurs in many breeds and is especially common in the dalmatian. The trait for deafness is tied to the genetics of coat colour, particularly in breeds with the merle or piebald gene. There is an increased risk of deafness with increasing amounts of white in the coat. How is deafness inherited? The mode of inheritance in dalmatians is thought to be autosomal recessive involving more than 1 gene (or incomplete penetrance may be involved), since dogs with normal hearing in both ears can produce bilaterally deaf puppies, and vice versa. Dogs with deafness in 1 ear can have pups that are deaf in both or neither. Statistically however, deaf parents are more likely to produce deaf pups. Dogs with an increased amount of white in their coats and blue eyes (discussed further below) are predisposed to congenital deafness. In breeds in which deafness is associated with merle colour, the trait appears to be autosomal dominant. In the bull terrier, Doberman pinscher, pointer and rottweiler, congenital deafness is thought to be an autosomal recessive trait. What breeds are affected by deafness? Deafness occurs in many breeds. The highest incidence is in the dalmatian, with studies from the US and the UK showing that 18 to 30% are unilaterally deaf, and 5 to 10% are bilaterally deaf. The condition is slightly more common in female dalmatians. Other breeds with a relatively high incidence of deafness are the English setter, Australian shepherd, border collie and Shetland sheepdog. There is a strong association of deafness with increased amounts of white colour in the coat and blue eyes (heterochromia iridis) in breeds with merle and piebald coat colouring. Merled breeds include the merled collie and Shetland sheepdog, Australian heeler, dapple dachshund (18% bilaterally deaf, 36% unilaterally deaf), harlequin great Dane, Norwegian dunkerhound, and old English sheepdog. Breeds with the piebald gene (which affects the amount and distribution of white areas) include the beagle, bull terrier, samoyed, great Pyrenees, Sealyham terrier, greyhound, English bulldog, English setter, and of course dalmatian. Congenital deafness is reported less commonly in many other breeds including the akita, cocker spaniel, Staffordshire terrier, Boston terrier, boxer, Catahoula leopard dog, Doberman pinscher, dogo Argentina, English springer spaniel, foxhound, German shepherd, greyhound, Jack Russell terrier, Kuvasz, Maltese terrier, miniature pinscher, miniature and toy poodle, papillon, Rhodesian ridgeback, rottweiler, St. Bernard, Scottish terrier, Shropshire terrier, Siberian husky, Walker American foxhound, West Highland white terrier, whippet. For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed. What does deafness mean to your dog & you? Pups lose their hearing a few to several weeks after birth. Signs of bilateral deafness may include aggressive play because the deaf pup does not hear cries of pain from littermates, and having to be jostled to waken. Unilateral deafness is much harder to spot. If your dog is deaf in only 1 ear, you will likely not even be aware of it. In training sessions, you may notice that your dog responds better to hand signals than verbal cues. One-sided deafness is generally not a problem, except in some working dogs for whom localization of sound is important. However it is much more difficult for bilaterally deaf dogs to lead a normal life, and breeders will generally opt for euthanasia of these pups. How is deafness diagnosed? If you suspect your dog is deaf, your veterinarian will recommend the BAER (Brainstem Auditory-Evoked Response) test since hearing loss can be very difficult to evaluate by clinical examination (ie. behavioural response to sounds). The BAER test is a painless and reliable means of detecting hearing loss in one or both ears, that is available at veterinary schools and referral centres. It can be used in puppies of 5 weeks of age on. Older pups and adult dogs may need to be sedated for the test. Dogs in breeds with a high incidence of deafness should be tested by the BAER test before being used for breeding, and pups should be tested before being sold. Hearing loss, if present, is complete - that is the dog either has normal hearing, or is totally deaf in 1 or both ears. How is deafness treated? Deafness can not be cured or treated, but dogs can generally accommodate very well, particularly if only deaf in 1 ear. They should not be bred. Because dogs that are deaf in both ears startle easily, are difficult to train, and are prone to accidents, they are usually euthanized as pups. As an alternative, an owner may train the dog to respond to hand signals or other visual cues, always restrain him/her on a leash or in a fenced yard, and be alert to the possibility of the dog biting someone if startled. FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN. Resources Ackerman, L. 1999. The Genetic Condition: A Guide to Health Problems in Purebred Dogs. pp 132-133. AAHA Press. Lakewood, Colorado. This reference has a good explanation of the heredity of the deafness trait and the association with merle and piebald coat colours. Wood, J.L.N., Delauche, A.J., Lakhani, L.H. 1996. The problem of inherited disease 6: deafness in Dalmatians. J. of Small Animal Practice. 37(11) : 559-561. Copyright © 1998 Canine Inherited Disorders Database. All rights reserved. Revised: October 30, 2001. This database is funded jointly by the Sir James Dunn Animal Welfare Centre at the Atlantic Veterinary College, University of Prince Edward Island, and the Canadian Veterinary Medical Association. |
related terms: Pulmonic stenosis, pulmonic stenosis with anomalous left coronary artery, type A pulmonic stenosis (pulmonary ostium hypoplasia), valvular pulmonic stenosis What is 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. How is pulmonic stenosis inherited? Pulmonic stenosis appears to be a polygenic threshold trait. What breeds are affected by pulmonic stenosis? Pulmonic stenosis is one of the most common congenital heart defects in all species. There is a breed predisposition in the following breeds of dog: The English bulldog and the mastiff are at most risk for pulmonic stenosis. In English bulldogs, pulmonic stenosis occurs commonly with an abnormal left main coronary artery branch, arising from a single right coronary artery. In this breed the condition is more common in males. There is also an increased risk of pulmonic stenosis in the beagle, wire-haired fox terrier, chihuahua, miniature schnauzer, samoyed, Boykin spaniel, West Highland white terrier, cocker spaniel, Airedale terrier, and Scottish terrier. For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a general consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed. What does pulmonic stenosis mean to your dog & you? In its milder forms, the slight thickening of the pulmonary valve will cause minimal or no obstruction and your dog will not be affected. However with more severe thickening of the valve, the obstruction to blood flow from the right side of the heart will cause varying degrees of heart damage which worsens with age. With moderate-to-severe pulmonic stenosis, your dog may experience signs associated with low cardiac output and/or right-sided heart failure, such as respiratory difficulties, fainting, tiring with exercise, abnormal cardiac rhythms, abdominal swelling due to an enlarged liver or the accumulation of fluid because of failing circulation, or sudden death. Based on your dog's physical examination and diagnostic tests such as chest x-rays and an electrocardiogram, your veterinarian will discuss with you the severity of the pulmonic stenosis. If there are significant changes evident, he or she will suggest further tests to determine the pressure gradient across the pulmonic valve. (Normally there is no pressure difference between the right ventricle of the heart, and the pulmonary artery to the lungs.) Where there is a pronounced pressure gradient, surgery to correct the stenosis should be considered. How is pulmonic stenosis diagnosed? The first indication that your dog has a problem may be when your veterinarian hears a heart murmur on an early physical examination. Alternately, you may see signs in your dog related to heart disease, such as fainting or fatigue with exercise. Your veterinarian will listen carefully to try to determine the location of the murmur and to differentiate it from an "innocent" murmur which disappears by about 6 months of age. If the murmur is significant, your veterinarian will suggest further tests such as a chest x-ray, electrocardiogram, and cardiac ultrasound to help determine the cause, and to see what changes if any have already occurred in the heart as a result of the defect. Once pulmonic stenosis has been diagnosed, Doppler echocardiography or cardiac catheterization can be done to measure the pressure gradient between the right ventricle and the pulmonary artery, to determine the severity of the obstruction. Based on these test results your veterinarian will discuss with you the long term prognosis for your dog and whether surgical correction of the defect should be considered. FOR THE VETERINARIAN: MURMUR: systolic ejection murmur, loudest in pulmonic area near left cranial sternal border, often equally loud along right cranial sternal border. ELECTROCARDIOGRAM: RV hypertrophy and right axis shift, right atrial enlargement, possibly arrhythmia associated with hypertrophy. RADIOGRAPHS: right ventricular hypertrophy , poststenotic dilation of pulmonary artery with distal pulmonary vessels reduced in size. ECHOCARDIOGRAPHY: primary means of diagnosis of pulmonic stenosis, typically see mild to moderate right atrial dilation, concentric RV hypertrophy, deformity and narrowing in the pulmonic valve region, and poststenotic dilation of the pulmonary artery. jugular pulses may be evident. In English bulldogs, pulmonic stenosis is commonly associated with a left coronary artery anomaly which has important implications for surgical correction. How is pulmonic stenosis treated? With mild-to-moderate stenosis, your veterinarian will monitor your dog. No other treatment is necessary unless clinical signs develop which are associated with heart disease. Surgery is an option in dogs with moderate-to-severe pulmonic stenosis, with different techniques recommended depending on the site of the stenosis. Because of the expertise and technical equipment required and the surgical risk involved, surgery to correct pulmonic stenosis is generally performed in a referral centre. Surgery is more risky if atrial fibrillation or congestive heart failure have developed. These conditions should be treated medically and the dog stabilized before surgery is considered. Medical management for congestive heart failure is similar no matter what the cause, and consists of medications to support the heart muscle and decrease the work load of the heart, together with dietary recommendations. FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN. Resources Bussardori, C. 1998. Breed related echocardiographic prognostic indicators in pulmonic and subaortic stenosis. ACVIM-Proceedings of the 16th Annual Veterinary Medical Forum: 140-142. Bonagura, J.D. and Darke, P.G.G. 1995. Congenital heart disease. In S.J. Ettinger and E.C. Feldman (eds.)Textbook of Veterinary Internal Medicine, p. 892-943. W.B. Saunders, Toronto. Patterson, D.F. 1996. The genetics of canine congenital heart disease. ACVIM-Proceedings of the 14th Annual Veterinary Medical Forum: 225-226. This reference has good information for breeders and veterinarians regarding screening and genetic counselling for congenital heart defects. Thomas, W.P. 1995. Therapy of congenital pulmonic stenosis. In J.D. Bonagura and R.W. Kirk (eds.) Kirk's Current Veterinary Therapy XII Small Animal Practice, p. 817-821. W.B. Saunders, Toronto. Copyright © 1998 Canine Inherited Disorders Database. All rights reserved. Revised: August 16, 2004. This database is funded jointly by the Animal Welfare Unit at the Atlantic Veterinary College, University of Prince Edward Island |
What is a 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. How are VSDs inherited? In the English bulldog and keeshond, inheritance is autosomal recessive, with variable expression. What breeds are affected by VSDs? This disorder occurs sporadically in many breeds. The English bulldog and keeshond are at increased risk for VSD. In either breed, a VSD may be part of the disorder Tetralogy of Fallot. For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a general consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed. What does a ventricular septal defect mean to your dog & you? The extent to which your dog will be affected depends on the size and location of the defect within the ventricular wall. Many dogs have small defects which may spontaneously close. With such defects there will no or very minor clinical effects. With larger defects, because of higher pressure in the left side of the heart, there will be a left-to-right blood flow across the defect. This means that the left side of the heart must work harder and that there will be extra blood circulated to the lungs, creating an abnormal load on them. Conditions that increase pressure in the right side of the heart (such as pulmonary hypertension) may result in a right-to-left shunt, also called a reverse shunt. Signs associated with this disorder may develop within months or years, depending on the significance of the defect, and include shortness of breath, exercise intolerance, sudden death due to an abnormal heart rhythm, or, with a reverse shunt, cyanosis (grey instead of pink mucous membranes). Your veterinarian will monitor your dog's progress and recommend treatment as required. This may include medications to support the heart and to reduce congestion in the lungs, a special diet, exercise restriction, and precautionary antibiotic therapy before procedures such as dentistry. Among puppies with large VSDs, it is probable that many die early, before 8 weeks of age or before they are examined by a veterinarian. How is a ventricular septal defect diagnosed? Often, as with most heart defects, the first indication of a problem is when your veterinarian hears a heart murmur on your pup's physical examination. Sometimes there is exercise intolerance or respiratory difficulty, but this is usually in an older dog or a young pup with a large defect where congestive heart failure has already developed. Some low-grade murmurs are "innocent" and disappear by 6 months of age, but if the murmur is significant, your veterinarian will suggest a diagnostic workup to determine the cause. S/he will listen very carefully to your dog's heart to determine where the murmur is loudest and when it occurs during the cardiac cycle. Other diagnostic aids include chest x-rays and an electrocardiogram (ECG). Echocardiography (an ultrasound) is generally required to determine the location and severity of a ventricular septal defect. Based on the results of these various tests, your veterinarian will discuss with you the prognosis and long term management of your pet. S/he will also be able to tell you whether any detectable change has occurred in the heart already as a result of the defect. FOR THE VETERINARIAN: MURMUR: harsh regurgitant holosystolic murmur, loudest in right intercostal spaces 2 to 4; also can often be heard cranially on left thorax. ELECTROCARDIOGRAM: normal or LV enlargement (with larger shunts); may develop right bundle branch block; may indicate right-sided enlargement if right-to-left shunt develops. RADIOGRAPHS: normal or left-sided enlargement; with larger shunts, increased prominence of pulmonary vasculature; right-sided enlargement if right-to-left shunt develops. OTHER: Clinical signs usually don't occur unless the pulmonary volume is more than 2 to 3 times normal. Most commonly, signs associated with a left-to-right shunt and left-sided heart failure are seen. Where secondary obstructive pulmonary vascular disease develops, so that pulmonary resistance exceeds that of the systemic vasculature, a right-to-left shunt develops (Eisenmenger's physiology). This is associated with cyanosis and polycythemia and has a very poor prognosis. How is a ventricular septal defect treated? Signs associated with heart disease are treated when and if they develop. Treatments include medications to support the heart and to reduce pulmonary congestion, a special diet, exercise restriction, and precautionary antibiotic therapy before procedures such as dentistry. There are 2 current surgical options available. Where a significant defect has been identified, but before right-to-left shunting has developed, pulmonary artery banding can be done to decrease the blood flow across the defect, thereby reducing the overload on the lungs and the left heart. Another procedure involves actual repair of the defect, but this requires open heart surgery and carries a high risk. Where to find more information? Bonagura, J.D. and Darke, P.G.G. 1995. Congenital heart disease. In S.J. Ettinger and E.C. Feldman (eds.)Textbook of Veterinary Internal Medicine, p. 892-943. W.B. Saunders, Toronto. Patterson, D.F. 1996. The genetics of canine congenital heart disease. ACVIM-Proceedings of the 14th Annual Veterinary Medical Forum: 225-226. This reference has good information for breeders and veterinarians regarding screening and genetic counselling for congenital heart defects. Copyright © 1998 Canine Inherited Disorders Database. All rights reserved. Revised: October 30, 2001. |
related terms: Type A aortic stenosis, Type B aortic stenosis, subvalvular aortic stenosis What is aortic stenosis? In aortic stenosis, there is a partial obstruction to the flow of blood as it leaves the left side of the heart (the left ventricle) through the main blood vessel (the aorta) that carries blood to the rest of the body. The obstruction ranges from small nodules to a fibrous band, most commonly just below the aortic valve ("subvalvular aortic stenosis"). Due to the obstruction, the heart must work harder to pump out an adequate blood volume. Clinical signs and long-term outcome depend on the degree of narrowing, or stenosis. How is aortic stenosis inherited? In Newfoundlands, this defect has been shown to have an autosomal dominant mode of inheritance, with variable expression. In the mildest form, the condition is undetectable and will not cause any problems for the dog. However the defect may still be passed on to offspring. The challenge for breeders and veterinarians is to identify affected dogs with very mild or no clinical signs of the disorder. What breeds are affected by aortic stenosis? Congenital aortic stenosis is probably the most common heart defect seen in large breed dogs. Newfoundland dogs have the highest risk for this disorder. It is also important in the golden retriever, Rottweiler, and boxer. There is a mildly increased risk of aortic stenosis in the German shepherd, German short-haired pointer, Great Dane,samoyed and bulldog. For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a general consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed. What does aortic stenosis mean to your dog and you? Dogs with mild stenosis will generally show no clinical effects and have a normal life expectancy. With moderate to severe stenosis, signs will be variable. Because of the narrowing in the aorta as the blood leaves the left ventricle, your dog's heart must work harder to pump an adequate volume of blood to the rest of the body. Depending on the degree of obstruction, your dog's heart may be able to compensate at rest but not keep up with the body's demands during exercise. Thus you may see reduced exercise tolerance - your dog just seems to run out of steam - or fainting due to inadequate blood supply to the brain. In response to the obstruction to blood flow, the heart muscle becomes thicker over time (left ventricular hypertrophy). As the condition progresses, your dog's heart becomes less able to compensate and you and your veterinarian may see signs associated with left-sided heart failure such as tiring on exercise, difficulty in breathing, coughing, and/or poor growth. Changes in the heart muscle can also lead to abnormal heart rhythms (cardiac arrythmias) and sudden death. Your veterinarian can do various tests (see below) to determine the severity of the defect. Based on the results, he or she will discuss with you the long-term prognosis, and ways to manage this condition in your dog. How is aortic stenosis diagnosed? In young animals (less than 6 months of age) there may be no clinical signs. Thus the first indication that your dog may have a problem may come when your veterinarian hears a heart murmur during physical examination. Some low-grade murmurs are "innocent" and disappear by 6 months of age, but if the murmur is significant, your veterinarian will suggest a diagnostic workup to determine the cause. He or she will listen very carefully to your dog's heart to determine the point of maximal intensity of the murmur and when the murmur occurs during the cardiac cycle. Other diagnostic aids include chest x-rays, an electrocardiogram (ECG) and/or ultrasonography if available. To determine the extent of the narrowing, the pressure gradient across the aortic valve (between the left ventricle and the aorta) can be measured using special procedures for which your veterinarian can refer your dog to a specialist. In an older animal or when the obstruction is pronounced there may be clinical signs associated with left-sided heart failure. Based on the results of these various tests, your veterinarian will discuss with you the prognosis and long term management of your pet. S/he will also be able to tell you if any (and how much) change has occurred in the heart already as a result of the stenosis. FOR VETERINARIAN: MURMUR: systolic, left hemithorax, radiates into thoracic inlet and up the neck, PMI left heart base (3rd to 4th intercostal space), may be equally loud at right heart base. ECG: may be normal, over time shows left ventricular enlargement, left axis shift, may show ST depression, may show ventricular arrhythmias RADIOGRAPHS: may see left ventricular enlargement, cranial aortic enlargement, left axis shift. Pulmonary vasculature is normal. ECHOCARDIOGRAPHY: left ventricular hypertrophy, subvalvular fibrous ring, post-stenotic dilation of aorta The arterial pulse may be of reduced intensity and slow to rise. Echocardiography (with Doppler) or cardiac catheterization is usually required to determine the severity of the defect. How is aortic stenosis treated? In dogs with mild aortic stenosis,there is no special treatment required. The dog should not be used for breeding and littermates should be carefully screened. Your veterinarian may suggest antibiotics in certain circumstances as a precaution against infection of the abnormal valve tissue. With moderate to severe stenosis, the dog's exercise should be restricted. Beta-blocking drugs may be prescribed by your veterinarian to try to minimize the effects of left ventricular hypertrophy. Your veterinarian will recommend other therapy if required to manage congestive heart failure. Medical management for congestive heart failure is similar no matter what the cause, and consists of medications to support the heart muscle and decrease the work load of the heart, together with dietary recommendations. Various surgeries have been attempted to alleviate the obstruction with limited success. The surgery itself carries a high risk, and there is little, if any, increase in survival rates compared with dogs whose condition is managed medically. FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN. Resources Bussardori, C. 1998. Breed related echocardiographic prognostic indicators in pulmonic and subaortic stenosis. ACVIM-Proceedings of the 16th Annual Veterinary Medical Forum: 140-142. Bonagura, J.D. and Darke, P.G.G. 1995. Congenital heart disease. In S.J. Ettinger and E.C. Feldman (eds.)Textbook of Veterinary Internal Medicine, p. 892-943. W.B. Saunders, Toronto. Patterson, D.F. 1996. The genetics of canine congenital heart disease. ACVIM-Proceedings of the 14th Annual Veterinary Medical Forum: 225-226. This reference has good information for breeders and veterinarians regarding screening and genetic counselling for congenital heart defects. Copyright © 1998 Canine Inherited Disorders Database. All rights reserved. Revised: August 18, 2003. This database is funded jointly by the Animal Welfare Unit at the Atlantic Veterinary College, University of Prince Edward Island, and the Canadian Veterinary Medical Association. |
related terms: demodectic mange, follicular mange, red mange What is demodicosis? Demodex canis is a mite that is present in small numbers in the skin of most healthy dogs. Nursing puppies acquire the mite from their mothers during the first few days of life, and in most dogs there will never be any associated problems. In some dogs however, the normal balance is disrupted due to an immune defect. The mites multiply by the thousands in the hair follicles causing inflammation, in a condition called demodicosis. Demodicosis may be localized - that is, confined to 1 or more small discrete scaly reddened areas of hair loss, most commonly on the face or front legs. This is usually seen in pups of 3 to 6 months of age, and most cases resolve spontaneously. Alternately, generalized demodicosis may develop, at anywhere from 3 to 12 months of age. This is a severe skin condition. The defect in the cell-mediated immune system which allows the development of generalized demodicosis is believed to be inherited. How is demodicosis inherited? unknown What breeds are affected by demodicosis? This condition is common in the Chinese shar pei. There is also an increased incidence of demodicosis in the Afghan hound, beagle, Boston terrier, boxer, bull terrier, chihuahua, collie, dachshund, dalmatian, Doberman pinscher, English bulldog, English pointer, German shepherd, Great Dane, Old English sheepdog, pit bull, pug, rottweiler, Staffordshire terrier. For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed. What does demodicosis mean to your dog & you? It is important to note that demodicosis is not infectious, to other pets or to people. The mite is present in small numbers in the skin of healthy dogs, but the condition of demodicosis only develops in some animals, who are believed to have a defect in their immune system. Demodicosis may be localized - a mild disorder confined to 1 or more small scaly reddened areas of hair loss, most commonly on the face or front legs. This is usually seen in pups of 3 to 6 months of age, and most cases resolve spontaneously. Generalized demodicosis on the other hand can be one of the most severe skin diseases in dogs. It starts out with local lesions that instead of disappearing, get worse and spread, generally on the head, legs and body. Secondary infections of the hair follicles occur, and large scaly crusted patches form which may eventually cover most of the dog. The deep skin infections can be complicated by resistant bacteria. Some dogs only develop demodicosis on the feet (demodectic pododermatitis). These lesions commonly become infected, are painful, and can be quite difficult to treat successfully. How is demodicosis diagnosed? Your veterinarian will do a simple procedure called a skin scraping to find the mites on your dog's skin. In the shar pei, because of the thick skin, a skin biopsy is often needed to make the diagnosis. This is a simple procedure done with local anesthetic, in which your veterinarian removes a small sample of your dog's skin for examination by a veterinary pathologist. For the veterinarian: A skin scraping for demodectic mites should be done in all skin diseases of the feet, pyodermas, and seborrheas. Remember that an occasional adult mite seen on skin scraping is consistent with normal skin. Over 50% of dogs with generalized demodicosis have a normocytic, normochromic, nonresponsive anemia, consistent with chronic infection. Many also have low thyroid hormone levels but they are not hypothyroid. How is demodicosis treated? Localized demodicosis: This is a mild disease that usually heals on its on within a few weeks, with or without treatment. Your veterinarian may suggest a mild parasitidal ointment or lotion to rub on the affected area. Whether or not your veterinarian recommends treatment, s/he will want to recheck your dog in about 4 weeks to make sure that the condition is not spreading. Generalized demodicosis: In most cases this serious disease can be treated successfully. Treatment can be lengthy and expensive but the majority of dogs recover completely. In most of the rest, the disorder can be well-controlled with monthly treatment. Most dogs recover after 4 to 8 treatments at bi-weekly intervals. Treatment for generalized demodicosis consists of clipping the dog's entire hair coat to allow better contact of the medication with the skin, removal of all crusts (which may require sedation or anesthesia depending on the extent), bathing with medicated shampoo to kill bacteria and remove debris, and application of a solution called Amitraz (Mitaban) to kill the mites. This regimen works in the majority of dogs. Another option is a course of oral medication, given daily for several months. Underlying skin infections and seborrhea (scaliness) must also be treated. For the veterinarian: In comparison to the initial scraping, a recheck skin scraping should reveal fewer mites, and fewer immature forms. If the lesions are spreading, there are more mites, and the ratio of immature forms to adults is high, than the dog should be treated for generalized demodicosis. Regional or generalized lymphadenopathy is another indicator of generalized demodicosis. See references below for detailed discussion of treatment, including of refractory cases. FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN. Resources Scott, D.W., Miller, W.H., Griffin, C.E. 1995. Muller and Kirk's Small Animal Dermatology. pp 417-432. W.B. Saunders Co., Toronto. Paradis, M. New approaches to the treatment of canine demodicosis in Veterinary Clinics of North America: Small Animal Practice November 1999 Copyright © 1998 Canine Inherited Disorders Database. All rights reserved. Revised: October 30, 2001. This database is funded jointly by the Sir James Dunn Animal Welfare Centre at the Atlantic Veterinary College, University of Prince Edward Island, and the Canadian Veterinary Medical Association. |
The Health Committee and BCA have no formal recommendation at this time on how breeders use results of tests to select breeding stock or make breeding decisions, BUT in keeping with the spirit of the BCA being the stewards of the bulldog breed, members are encouraged to take advantage of advances in testing, genetics and medical science to always strive to produce the soundest animals possible with the goal of continuously improving the genetic health of the breed as a whole. |
