Great Dane health & Tests explained

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CAUSE

Canine dilated cardiomyopathy (DCM) is a primary disease of cardiac muscle that results in a decreased ability of the heart to generate pressure to pump blood through the vascular system. The definitive cause of canine DCM is the subject of debate, although a number of factors including nutritional, infectious, and genetic predisposition have been implicated. The fact that canine DCM occurs at a higher incidence in specific breeds suggests a heritable genetic component to this disease, although it is likely that it’s etiology is multifactorial. Breeds predisposed to DCM include the Doberman Pinscher, the Great Dane, the Boxer, and the Cocker Spaniel. Dietary carnitine deficiency may play a role in some cases of Boxer DCM, and taurine responsive DCM has been identified in Cocker Spaniels.

CLINICAL SIGNS

DCM is characterized by dilation of the ventricles with ventricular wall thinning. In many cases, dilation of all four chambers of the heart is seen. The ability of the heart to serve as a pump is diminished, and clinical signs of DCM occur secondary to either decreased delivery of oxygenated blood to the body (lethargy, weakness, weight loss, collapse), or to congestion of blood in the lungs (coughing, increased respiratory rate and/or effort, abdominal distention) or both. Cardiac dilation, decreased oxygen supply, and increased oxygen demand secondary to elevated heart rate and ventricular wall stress may predispose to the development of cardiac arrhythmias arising in either the atria (atrial fibrillation, supraventricular tachycardia) or in the ventricles (ventricular premature complexes, ventricular tachycardia). Arrhythmias may predispose affected dogs to sudden death.

DIAGNOSIS

DCM is diagnosed by echocardiography, which demonstrates the chamber dilation and indices of decreased pump function characteristic of the disease. Thoracic radiography is useful to evaluate pulmonary (lung) tissue and vessels, and may show evidence of fluid accumulation in the lungs (pulmonary edema) or around the lungs (pleural effusion). Electrocardiography may be used to characterize heart rhythm and to rule out arrhythmias; and in some cases, a 24 hour electrocardiogram (Holter monitor) may be recommended to more accurately characterize cardiac rhythm.

TREATMENT

Treatment of DCM is directed at improving systolic (pump) function of the heart, dilating the peripheral blood vessels to decrease ventricular workload, eliminating pulmonary congestion if present, and controlling heart rate and cardiac arrhythmias if present. These treatment goals are addressed by the administration of cardiac medications, which may be delivered by injection in emergent situations, or orally in patients that are more stable.

PROGNOSIS

Canine DCM can be a devastating disease, and the prognosis for dogs with DCM is variable depending upon breed and status at presentation. The prognosis for Doberman Pinschers with DCM, for example, is less favorable than in other breeds, while DCM in Cocker Spaniels may be relatively slowly progressive. Patients that present in congestive heart failure generally have a worse prognosis than those that are not in congestive heart failure at presentation. Irrespective of this, medical therapy may provide significant improvement in lifespan and quality of life in affected dogs.

Read more here. 

Source text and image: Cornell University College of Veterinary medicine https://www.vet.cornell.edu/hospitals/companion-animal-hospital/cardiology/canine-dilated-cardiomyopathy-dcm

Hip dysplasia (HD) is a common inherited orthopaedic problem of dogs and a wide number of other mammals. Abnormal development of the structures that make up the hip joint leads to subsequent joint deformity. ‘Dysplasia’ means abnormal growth. 

The developmental changes appear first and because they are related to growth, they are termed primary changes. Subsequently these changes may lead to excessive wear and tear. The secondary changes may be referred to as (osteo)arthritis (OA), (osteo)arthrosis
or degenerative joint disease (DJD).

Later one or both hip joints may become mechanically defective. At this stage the joint(s) may be painful and cause lameness. In extreme cases the dog may find movement very difficult and may suffer considerably. 

Structure and function

The hip joints of land animals and even some birds are remarkably similar. Overall the design has withstood the test of time and
is probably close to anatomical perfection. When athletic activity is required, the normal hip is an ideal means of transferring power from the muscles to drive the body forwards with maximum strength and speed. It is the close relationship of the femoral head (ball) and acetabulum (socket) which enables rapid changes of direction. The entire hip joint is a unit comprising the bony structures contained within a joint capsule and supported by ligaments, tendons and muscles together with all their blood vessels and nerves. The large joint surfaces are lubricated by synovial fluid. The viscosity (oiliness) of this fluid ensures smooth, pain-free joint movement. It is not surprising that any variation from this ideal can have severe consequences.

Developmental demands

It is argued that dogs are not born with hip joints already affected by dysplasia (unlike humans) but that any faults in development will tend to escalate with time, particularly during the rapid growth phase from about 14 to 26 weeks of age. However, changes begin as the very young puppy starts to become active and continue until the puppy is skeletally mature. Wear and tear of the deformed joint results in varying amounts of inflammation and degeneration which lead to more deformity. This progressive deformation is sometimes referred to as remodelling. Some dogs may treble their size and body weight in just three months of adolescence so it is not surprising that there are many critical factors for the puppy at this stage. All the essential nutritional requirements for skeletal growth must be available in the right proportions and at the right time. The environment within which the dog is raised, including the type and intensity of exercise, growth rate and body weight are significant influences. However inheritance is a major factor and this is something which we are able to influence by the selection of breeding animals.

Signs

As HD can include joint looseness (laxity), inflammation, pain, new bone formation and bone erosion, it may cause a range of observable signs from normal to minor changes in gait (in the mildly affected cases) to obvious lameness, stiffness after rest and exercise intolerance and pain. As some individuals and breeds may be more stoical than others there is no way of estimating the severity of HD in any dog by observation alone. A veterinary surgeon’s physical examination will provide a more reliable assessment by revealing limitation of joint movement, muscle wasting and pain in the joint(s). Usually a dog with HD does not demonstrate discomfort by yelping,

as pain is likely to be dull and continuous rather than sharp and acute. The dog may, though, groan while resting or getting up.

Radiography is the only means of determining the presence or absence of HD. This is an X-ray examination to look at the relative shape and positions of the femoral head

and acetabulum and the presence and degree of any secondary changes.

Causes

It is known that two factors determine whether HD will occur, and if so, how bad it will be. These are hereditary and ‘environmental’ factors. ‘Hereditary’ relates to the genetic code passed to the offspring by both parents and environmental are all the outside influences which alter and shape the growth and functions of the bones, cartilage, ligaments, tendons and muscles of the body. In simple terms the genetic code is rather like an architect’s plan (genotype), while the environment is like the builder and his materials (phenotype). In HD the architect has made some errors but the builders have a great influence on how things finally look and function.

Treatment

It is possible to alleviate some or most of
the signs of pain and limitation of movement caused by HD. Sophisticated medications
and various surgical procedures are now available. Applied heat, massage, good bedding, exercise and weight management
as well as nutrition and physiotherapy also play a part in caring for a dog affected by HD. Professional advice is always necessary to ensure that the best strategy is developed.

The hip score is the sum of the points accrued for each of nine radiographic features in each hip joint. The lower the score the less the degree of HD present. The minimum (best) score for each hip is zero and the maximum (worst) is 53, giving a range for the total score of 0 to 106.

Source: British Veterinary Association (BVA)

https://www.bva.co.uk/media/2797/chs-hip-dysplasia-2019-v2-web-170419.pdf

ELBOW DYSPLASIA 

Elbow dysplasia is a common inherited orthopaedic problem in dogs where the elbow doesn’t develop properly.

Elbow dysplasia includes a number of specific abnormalities or problems that affect different areas of the elbow joint. These cause problems by affecting the growth of the cartilage which forms the surface of the joint or the structures around it. Even a small change in the shape of one part of the joint can have major consequences for the joint function, leading to lameness (unable to walk correctly), osteoarthritis (a common form of arthritis), pain and serious effects on the health, behaviour and welfare of the dog.

WHAT ARE THE SIGNS?

Signs of elbow dysplasia in dogs vary between individuals and breeds. Some visible signs include:

• Decreased range of motion
• Limping
• Unwilling to exercise
• Unusual movement after rest or exercise
• Groaning while resting or getting up
• Signs of pain when moving the elbow

A vet's physical examination will provide a more reliable assessment and radiography is the only way of determining whether a dog has elbow dysplasia.

HOW TO TREAT IT?

Treatment methods vary depending on the nature and severity of the problem. Non-surgical treatment can involve weight restriction and exercise control. Drugs may be used to relieve pain and inflammation. In some dogs, surgery and/or physiotherapy may be advised.

Source text and image: British Veterinary Association (BVA) https://www.bva.co.uk/canine-health-schemes/elbow-scheme/

What is Gonioscopy? 

Gonioscopy is a type of eye exam that looks for signs that a dog is affected by a painful and blinding disease known as primary glaucoma. How much the eye is affected is recorded and given as a grade. This grade can be used to help make health focused breeding decisions that reduce the risk of producing puppies that grow up to be affected by primary glaucoma.

What is Primary Glaucoma 

Primary glaucoma is an inherited condition caused by a build-up of pressure in the eye. This increased pressure occurs because the eye is not able to properly drain away enough of the fluid made inside.

Primary glaucoma can be divided into two types:

• Primary open angle glaucoma (POAG)
• Primary angle closure/ closed angle glaucoma (PCAG).

The information below relates to gonioscopy for primary angle closure/ closed angle glaucoma only.

What are the clinical effects of primary glaucoma? 

Clinical signs of the primary angle closure/ closed angle glaucoma are:

• depression
• signs of eye pain, such as excessive blinking and avoiding bright light
• cloudiness at the front of the eye
• a reddened eye
• a dilated non-responsive pupil
• blindness
• 
  

What causes primary glaucoma? 

Primary glaucoma is caused by a build-up of pressure that occurs because some of the fluids that are produced in the eye can’t drain away properly.

Primary angle closure/ closed angle glaucoma is linked to a problem with the drainage angle. This is the angle between the iris (the coloured part of the eye) and the cornea (the clear window part of the eye). This issue with the angle is termed pectinate ligament abnormality (PLA), but is also known as goniodysgenesis (gonio = angle, dysgenesis = defective development).

Source text and image Kennel Club UK: https://www.thekennelclub.org.uk/health-and-dog-care/health/getting-started-with-health-testing-and-screening/gonioscopy/

Inherited myopathy of Great Danes (IMGD) is a rapidly progressive muscle myopathy with an age of onset around six months. The disease is inherited in an autosomal recessive fashion thus two copies of the IMGD mutation are needed for a dog to be affected.

IMGD results from a single base change in the bridging integrator 1 (BIN1) gene. Affected dogs exhibit exercise intolerance and progressive muscle atrophy. Research data suggest that only 20% of affected dogs survive to adulthood with acceptable quality of life. Dogs with one normal and one mutated BIN1 gene (carriers) are unaffected, but breeding two carriers together would be predicted to produce 25% affected offspring and 50% carriers.

Testing for IMGD assists owners and breeders in identifying affected and carrier dogs. Breeders can use results from the test as a tool for selection of mating pairs to avoid producing affected dogs.

CLINICAL SIGNS

Onset – 6 to 12 months. Signs include; difficulty exercising, tremors (particularly brought on by exercise), weakness, muscle wasting, abnormal posture or gait.

HOW IS INHERITED?

The disease is described as an autosomal-recessive condition. This means that a dog must inherit two copies of an abnormal gene (one from its mother and one from its father) before its health is affected. A dog that inherits only one copy of the abnormal gene (from its mother or its father) will have no signs of the disease, but will be a carrier and may pass the gene on to any offspring.

Source text vgl.ucdavis.org

Photo https://www.researchgate.net/figure/The-canine-Inherited-Myopathy-of-Great-Danes-results-from-a-BIN1-mutation-in-the-exon-11_fig8_282298719