Genetic diseases
Genetic conditions are a problem in some dogs, particularly purebreeds. For this reason many of the national kennel clubs require that dogs with certain genetic illnesses or who are deemed to be carriers cannot be registered. Some of the most common conditions include hip dysplasia, seen in large breed dogs, von Willebrand disease, a disease that affects platelets that is inherited in Doberman Pinschers, entropion, a curling in of the eyelid seen in Shar Peis and many other breeds, progressive retinal atrophy, inherited in many breeds, deafness, and epilepsy, known to be inherited in Belgian Shepherd Dogs, German Shepherd Dogs, Cocker Spaniels, and St. Bernards.[21]
Subaortic stenosis, or SAS, is a genetic ailment that causes a narrowing of the passage of blood between the heart and the aorta. This leads to heart problems and sometimes sudden death. It affects larger breeds such as the Newfoundland Dog and the Golden Retriever.[22] In some dogs, such as collies, the blue merle or harlequin coloring is actually the heterozygote of a partially recessive gene preventing proper development of the nervous system; therefore, if two such dogs are mated, on the average one quarter of the puppies will have severe genetic defects in their nervous systems and sensory organs ranging from deafness to fatal flaws.
Skin diseases
Skin diseases are very common in dogs. Atopy, a chronic allergic condition, is thought to affect up to 10 percent of dogs.[23] Other skin diseases related to allergies include hot spots and pyoderma, both characterized by secondary bacterial infections, food allergy, ear infections, and flea allergy dermatitis. Canine follicular dysplasia is an inherited disorder of the hair follicles resulting in alopecia (baldness). Mange is an infectious skin disease caused by mites. Endocrine diseases such as hypothyroidism and Cushing's syndrome can also manifest as skin problems like alopecia or recurring bacterial infections.
Orthopedic diseases
Orthopedic diseases in dogs can be developmental, hereditary, traumatic, or degenerative. Because of the active nature of dogs, injuries happen frequently. One of the most common of these is an anterior cruciate ligament injury, a condition which often requires surgery. Bone fractures are a frequent occurrence in outdoor dogs due to trauma from being hit by cars. Degenerative joint disease is common in older dogs and is one of the most likely reasons for prescription of non-steroidal anti-inflammatory drugs.
Hereditary orthopedic diseases are mainly found in purebred dogs. Hip dysplasia is a common problem that primarily affects larger breeds. Hip dysplasia is a defect in the shape of the hip joint which can, depending on the degree of hip luxation, be quite painful to the dog as it ages. Over time it often causes arthritis in the hips. Dysplasia can also occur in the elbow joint. Luxating patellas can be a problem for smaller breeds. It can cause lameness and pain in the hind legs.
Developmental orthopedic diseases include panosteitis and hypertrophic osteodystrophy. Panosteitis occurs in large and giant breed dogs usually between the age of five and fourteen months and manifests as fever, pain, and shifting leg lameness. Hypertrophic osteodystrophy is also seen in young large and giant breed dogs and is characterized by pain, lameness, fever, and swelling of the long bone metaphysis.
Tumors and Cancer
Both benign and malignant tumors are seen in dogs. Common benign tumors include lipomas, non-viral papillomas, sebaceous gland adenoma, and perianal gland adenomas.
Frequently seen cancers include lymphoma, melanoma, mast cell tumors (which are considered to be potentially malignant, even though they may have benign behavior),[24] and osteosarcoma (bone cancer).
Certain breeds are more likely to develop particular tumors. The Golden Retriever is especially susceptible to lymphoma, with a lifetime risk of 1 in 8.[25] Boxers and Pugs are prone to multiple mast cell tumors.[24] Scottish Terriers have eighteen times the risk of mixed breed dogs to develop transitional cell carcinoma, a type of urinary bladder cancer.[26]
Gastrointestinal diseases
Due to the indiscriminate nature of a dog's appetite, gastrointestinal upset is a frequent occurrence in dogs. The most common symptoms are anorexia, vomiting, and diarrhea. Foreign body ingestion can lead to acute obstruction of the gastrointestinal tract, a very dangerous condition. Acute pancreatitis can also result from dietary indiscretion.
Bloat and gastric torsion
Breeds with deep, narrow chests, such as the Great Dane or St. Bernard, are susceptible to a syndrome of gastric torsion and bloat. The stomach twists on its supporting ligaments, sealing off the exits, and the contents begin to generate gas pressure which is very painful and rapidly causes shock and necrosis of large areas of stomach tissue. It can be fatal within a few hours. Dogs who have experienced bloat are very susceptible to recurrences. Treatment involves stabilization and abdominal surgery to tack the dog's stomach down to prevent recurrence (gastropexy).
Eye diseases
Eye diseases are common in dogs. Cataracts, glaucoma, and entropion are seen in both dogs and humans. Canine-specific eye diseases include progressive retinal atrophy, Collie eye anomaly, sudden acquired retinal degeneration, and cherry eye. Injury to the eye can result in corneal ulcers.
The frequency of bilateral glaucoma with a genetic base in purebred dogs is higher than in any species except humans.[27] Cataracts in dogs either have a genetic base or can also be caused by diabetes. Nuclear sclerosis resembles a cataract but is actually a normal age-related change.
Vestibular disease
Elderly dogs are susceptible to an unusual form of intense vertigo, known as old dog vestibular disease, the cause of which is unknown, or idiopathic. Signs include nausea, difficulty or the complete inability to stand, head tilt, circling, and nystagmus (the movement of the eyes in a repetitive jerking motion, usually horizontal). The signs may improve rapidly or take a few days. While most cases are idiopathic, vestibular signs can also be caused by inner ear disease, a brain tumor, or rarely a stroke. The major risk of idiopathic cases is that the dog is often unable to eat, drink, or go outside to urinate or defecate. These cases must receive supportive therapy of intravenous fluids and nutrition; a light sedative is sometimes administered, as the dog may be very stressed by the experience.
Heart disease
Older, small breeds of dogs are prone to congestive heart failure due to degeneration of the mitral valve. This condition is known to be inherited in Cavalier King Charles Spaniels. Degenerative valve disease is the most common form of heart disease in dogs.[28] Mitral insufficiency leads to turbulent blood flow and increased pressure in the left atrium. This causes increased pressure in the pulmonary blood vessels and pulmonary edema (a build-up of fluid in the lungs). Decreased output of blood by the left ventricle causes the body to compensate by increasing sympathetic tone and activating the renin-angiotensin-aldosterone system (RAAS). Increased sympathetic tone leads to increased peripheral vascular resistance and increased heart rate and contractility of the heart muscle. Chronic elevation of sympathetic tone damages the heart muscle. Activation of the RAAS results in increased retention of water and sodium by the kidneys, vasoconstriction, and other effects that result in increased blood volume. It also results in an increase in diastolic pressure and leads to pulmonary edema. Treatment for congestive heart failure nearly always includes two types of drugs that address these concerns: diuretics (especially furosemide), which decrease blood volume, and ACE inhibitors, which interrupt the RAAS.
Cardiomyopathy, or disease of the heart muscle, is also seen in dogs and is associated with large breeds (the exception being Cocker Spaniels, a medium-sized breed). Dilated cardiomyopathy is seen in Great Danes, Irish Wolfhounds, St. Bernards, Dobermanns, Boxers, and other large breeds. Dobermanns, in addition to heart muscle failure, are prone to ventricular arrhythmias. Boxers often present with weakness and fainting due solely to arrhythmias - there is no heart muscle failure at the time of diagnosis. They do, however, eventually develop congestive heart failure, if they do not die suddenly due to an arrhythmia.[29]
Other diseases
Other diseases affecting dogs include endocrine diseases, immune-mediated diseases, and reproductive diseases. Diabetes mellitus, Cushing's syndrome, Addison's disease, and hypothyroidism are the most common endocrine diseases. Immune-mediated hemolytic anemia is a devastating disease that causes severe anemia in dogs through destruction by the immune system. It has been associated with vaccinations and certain drugs, although many cases are idiopathic. A similar but less severe immune disease is immune-mediated thrombocytopenia, characterized by destruction of platelets by the immune system. Symptoms include bruising and petechiae (pinpoint bruising, often seen in the mouth). Common reproductive diseases include pyometra (distension of the uterus with pus), mammary tumors, and benign prostatic hyperplasia.
As rewritten from Wikipedia
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