» Boxer health testing

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Health testing is a very important part of breeding boxers and more people need to be aware. This page provides an explanation of genetic disease and descriptions of those diseases prevalent in boxers, followed by a list of the tests available to screen for those diseases and determine genetic fitness for breeding.

The American Boxer Club’s recommended health screening programme for breeding boxers can be viewed at http://www.americanboxerclub.org/health-screening.html

What is a genetic disease?

A genetic disorder is one in which an abnormality in the genetic make-up (the genome) of the individual plays a significant role in causing a disease or condition. While some disorders can occur as the result of spontaneous mutation, most genetic disorders are inherited. These diseases are heart-breaking because they can impact severely on the quality and length of life of the affected dog - who is generally a well-loved family member by the time the condition is apparent.

The frequency of inherited conditions can be greatly reduced through good breeding practices. For this to occur, we need to know how the disease is inherited, how to identify the condition as early as possible, and ways to recognize carriers of the disease who are not clinically affected. Where testing regimes are available, it is important that all potential breeding stock are screened. Animals found to be affected by, or are carriers of a disease should not used for breeding.

Genetically inheritable diseases prevalent in boxers

  • Aortic stenosis/sub-aortic stenosis (AS/SAS) is one of the most common heart defects occurring in boxers. Stenosis is narrowing of the aorta, right below the aortic valve, which forces the heart to work harder to supply blood. Reduced blood flow can result in fainting and even sudden death. The disease is inherited but its mode of transmission is not known at this time. Diagnosis must be made by a veterinary cardiologist, after detection of a heart murmur. Breeding dogs must be properly screened for this disease and affected dogs must not be bred from.
  • Boxer cardiomyopathy is an electrical conduction disorder which causes the heart to beat erratically (to have an arrhythmia) some of the time and can result in weakness, collapse or sudden death. These arrhythmias are difficult to detect with any certainty by listening to the heart with a stethoscope, unless they are very frequent thus the first sign of the disease may be fatal. Cardiomyopathy is a genetically inheritable condition with devastating results. Because a dog cannot be cleared of cardiomyopathy by a routine veterinary examination and the disease may not show itself until after a dog reaches breeding age, it is important that all breeding stock are properly screened for this disease.

Boxer cardiomyopathy is a distinct disease from the dilated cardiomyopathy common in some other breeds. Other names for BCM are Boxer Arrythmic Cardiomyopathy (BAC), Familial Ventricular Arrhythmia (FVA) and Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC).

  • Hip dysplasia is an inheritable malformation of the hip joint leading to osteoarthritis. The hip joint is a ball and socket joint, where the top of the thigh bone (femur) fits into a socket in the pelvis. The bones are held in place by ligaments. Hip dysplasia occurs when the socket is poorly formed or the ligaments are loose, enabling the ball of the femur to subluxate – to slide part way out of its socket. Over time this causes degeneration of the joint (osteoarthritis) and the dog suffers pain and becomes weak and lame in the hind end. Hip dysplasia is a progressive disease, meaning that it becomes worse with time.

Hip dysplasia has polygenic inheritance, meaning it is caused by the inheritance of multiple genes. It is not yet known how many, or which genes are involved. Factors that can make the disease worse include excess weight, excess or prolonged exercise before maturity, a fast growth rate, and high-calorie or supplemented diets.

  • Hypothyroidism describes an inactive thyroid gland which can be responsible for such conditions as epilepsy, alopecia or hair loss, obesity, lethargy, hyperpigmentation, pyoderma and other skin conditions. While not considered life threatening, the quality of life for a dog suffering from hypothyroidism is much reduced.
  • Corneal dystrophy is an inherited abnormality that affects one or more layers of the cornea. Both eyes are usually affected, although not necessarily symmetrically. Chronic or recurring shallow ulcers may result, depending on the corneal layers affected.
  • Demodectic mange. The demodex mite lives on the skin of all dogs, and is passed to puppies by their dam. In healthy dogs, this mite causes no problems. However, demodectic mange can occur when a dog has a weakened or compromised immune system. The American Academy of Veterinary Dermatology passed a resolution in 1983 suggesting that all dogs that develop generalised demodex should be neutered or spayed as there is a genetic link to the development of generalised demodectic mange.

Demodectic mange can occur in localised form, which is characterised by a few spots that do not itch. These patchs usually appear on head, neck and fore limbs. Ninety percent of those puppies that develop localised demodex will heal on their own. Ten percent of those puppies will go on to have generalised demodex.

  • Cancer. Boxers are particularly prone to the development of mast cell tumours, lymphoma and brain tumours. White boxers, and coloured boxers with white markings should be protected from the sun as they are liable to develop skin cancer if allowed to burn.
  • Bloat or Gastric dilatation-volvulus (GDV) is a very serious condition that occurs when the stomach becomes distended with air, and then twists on itself while dilated. This interferes with the blood supply digestive organs, blocks the passage of food, thus leading to worse bloat. The distended stomach impedes the normal return of blood to the heart, causing a decrease in blood pressure and drastically reduced cardiac output. Blood/oxygen-deprived tissues start to die, releasing toxins into the blood stream which among other adverse effects, cause serious disturbances in heart rhythms (cardiac arrhythmias). Dogs affected by bloat can die within hours.

Dogs most susceptible to bloat are the large, deep-chested breeds, in whom the stomach appears to be more mobile within the abdomen. Risk factors are: hereditary predisposition, over-eating (large meals), rapid eating, raised feeders, pre-moistening of dry food preserved with citric acid, feeding dry food with a fat in the top four ingredients. The risk of bloat increases with age. Feeding a food with a rendered meat ingredient, inclusive of bone, in the first four ingredients decreases the risk of bloat.

The Purdue veterinary research team, who conducted a research study in 2000 into the risk factors associated with bloat concluded these are the things you can do to help prevent bloat:

a.. The strongest recommendation to prevent GVD (bloat) should be to not breed a dog that has a first degree relative that has had bloat. This places a special responsibility on an owner to inform the breeder should their dog bloat.
b.. Do not raise the feeding dish.
c.. SLOW the dog's speed of eating.

  • Allergies. Boxers are rather prone to allergies, which can be environmental or food related. These often translate into itchy, scaly and sometimes infected skin. Boxers do not tend to do well on foods that have a high grain content, particularly those including corn, wheat or beet pulp.
  • Deafness. About 20% of white boxers are deaf, due to their lack of pigmentation and suppression of blood supply to the cochlea (inner ear). White boxers should not be bred since the genes responsible for deafness in whites are inheritable. Breeding dogs that carry the extreme white spotting gene (white boxers have two copies of this gene, see http://www.boxerworld.com/forums/view_boxer-coat-colour.htm) will cause pigment dilution in all offspring and increase the incidence of deafness throughout the breed.

Tests available to screen for serious genetic diseases and which should be undertaken on all breeding boxers

Holter Monitor: A 24-hour EKG (electrocardiogram) that tests for the presence of PVCs (Premature Ventricular Contractions). This test screens for Boxer Arrythmic Cardiomyopathy, and should be repeated yearly. There is, at this time, no set number of PVCs that would be considered "affected" with BAC. A zero or low number of PVCs does not mean that the dog is free of BAC, it only means that the dog was not exhibiting PVCs during that 24-hour period. However, consistent zero/low readings on yearly Holtering would indicate a higher possibility that the dog is not affected with BAC.
For more information, please visit http://www.americanboxerclub.org/healthtbc.html and read these articles: Reports From The Health And Research Committee, May 2000; Information on Boxer Cardiomyopathy; Report and Article by Dr. Meurs; Article on Boxer Cardiomyopathy; Information on Holter monitoring.

Doppler Echocardiogram: An ultrasound of the heart that detects abnormal flow velocities and allows for the diagnosis and quantification of the severity of Aortic Stenosis. A clear Doppler after the dog is 24 months of age is considered conclusive (the dog does not have AS). Some studies show that Aortic Stenosis is a polygentic (cause by several genes) disease, so two clear parents can produce affected offspring.

Cardiac Auscultation: A stethoscopic examination of the heart that detects murmurs that may be indicative of AS. According to the UK Breed Council Control Scheme, a dog that is found to have no murmur or a Grade 1 murmur upon auscultation after 12 months of age is considered normal and acceptable for breeding.

OFA Heart: The OFA will certify dogs as "normal" if they are found, upon ausculatation after 12 months of age, to be without a cardiac murmur, or with an innocent heart murmur that is found to be otherwise normal by virtue of an echocardiographic examination which includes Doppler studies. Screening can be done by a general practice veterinarian, a specialist, or a cardiologist. Submission of results is voluntary. OFA Heart testing may detect Aortic Stenosis, although mild cases may go unnoticed if auscultation is performed by a general practice vet. It will not detect Boxer Arrythimic Cardiomyopathy.
OFA has developed a database registry for Holter Monitor results for the Boxer breed. Submission of results is voluntary and they are confidential.
For more information on all OFA tests, please visit http://www.offa.org

**All heart testing should be performed by a board-certified veterinary cardiologist.**

OFA Hips (Orthopedic Foundation for Animals Inc): An X-ray of the pelvic joint to screen for hip dysplasia. Ratings of "Excellent," "Good," or "Fair" are considered to be free of HD. One view is taken, the dog is commonly sedated or anesthetized but this is not required, and submission of results is voluntary. The X-rays must be taken after the dog is 24 months of age. There are several other factors that influence the expression of HD, including diet and environment, and two clear parents can produce dysplastic puppies.

PennHip (University of Pennsylvania Hip Improvement Program): An X-ray of the pelvic joint to screen for hip dysplasia. Laxity of the hips is evaluated and compared to the breed average (the Boxer breed average is .48 laxity). Three views are taken, the dog must be sedated or anesthetized, and submission of results is mandatory. PennHip X-rays can be taken as early as 16 weeks, although most feel a definitive rating should wait until the dog is older.

OFA Thyroid: A blood test to detect autoimmune thyroiditis. Annual testing through 4 years of age is recommended, after that, testing every other year should suffice. A negative at any one time will not guarantee that the dog will not develop thyroiditis. Most vets do not perform a full thyroid panel - as a result, there are only six laboratories that are approved for OFA thyroid certification: the veterinary laboraties at Michigan State University, Cornell University, University of Guelph, University of Minnesota, University of California - Davis, and Texas A&M University.

CERF (Canine Eye Registration Foundation) testing screens for heritable eye diseases such as PRA (Progessive Retinal Atrophy). Results are kept in a centralized, national registry. Testing must be performed by a member of the American College of Veterinary Ophthalmologists. Submission of results is mandatory but confidential. CERF screening is repeated yearly.

  If you want to discuss about these topics, visit our Boxer Health and Puppy Matters forums.




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