Dog health

The health of dogs is a well studied area in veterinary medicine.

Dog health is viewed holistically; it encompasses many different aspects, including disease processes, genetics, and nutritional health, for example. Infectious diseases that affect dogs are important not only from a veterinary standpoint, but also because of the risk to public health; an example of this is rabies. Genetic disorders also affect dogs, often due to selective breeding to produce individual dog breeds. Due to the popularity of both commercial and homemade dog foods, nutrition is also a heavily studied subject.

Diseases

Some diseases and other health problems are common to both humans and dogs; others are unique to dogs and other animals. Dogs are susceptible to various diseases; similarly to humans, they can have diabetes, epilepsy, cancer, or arthritis.

Timely vaccination can reduce the risk and severity of an infection. The most commonly recommended viruses to vaccinate dogs against are:

* Rabies
* CDV ( canine distemper)
* CAV-2 ( canine hepatitis virus or adenovirus-2)
* Canine herpesvirus
* Canine influenza
* CPV-2 (canine parvovirus)
* Kennel cough
* Leptospirosis
* Lyme disease

Infectious diseases

An infectious disease is caused by the presence of organisms such as viruses, bacteria, fungi, or parasites (either animalian or protozoan). Most of these diseases are spread directly from dog to dog, while others require a vector such as a tick or mosquito. Certain infectious diseases are a concern from a public health standpoint because they are zoonoses (transmittable to humans)

Viral diseases

Viral diseases in dogs can be serious, especially in kennels.

Bacterial diseases

Bacterial diseases in dogs are usually not contagious from dog to dog; instead they are usually the result of wound colonization, opportunistic infections secondary to decreased resistance (often the result of viral infections), or secondary to other conditions ( pyoderma secondary to skin allergies or pyometra secondary to cystic endometrial hyperplasia). These examples are not considered infectious diseases because they do not satisfy Koch's postulates – for example ''Staphylococcus intermedius'', a commonly isolated bacteria from skin infections in dogs, would not cause pyoderma when introduced to a healthy dog. In all likelihood that type of bacteria is already present on the skin of a healthy dog.

There are some bacteria that are contagious from dog to dog. The most notable of these are '' Bordetella bronchiseptica'', one of the causes of kennel cough, ''Leptospira'' sp, which cause leptospirosis, and ''Brucella canis'', cause of brucellosis in dogs. There are also common tick-borne bacterial diseases, including Lyme disease, ehrlichiosis, and Rocky Mountain spotted fever.

Leptospirosis is a zoonotic disease caused by bacteria of the genus ''Leptospira''. Humans and dogs become infected through contact with water, food, or soil containing urine from infected animals. This may happen by swallowing contaminated food or water or through skin contact, especially with mucosal surfaces, such as the eyes or nose, or with broken skin. In dogs, transmission most commonly occurs by drinking puddle, pond, or ditch water contaminated by urine from infected wildlife such as squirrels or raccoons. The liver and kidney are most commonly damaged by leptospirosis. Vasculitis can occur, causing edema and potentially disseminated intravascular coagulation (DIC). Myocarditis, pericarditis, meningitis, and uveitis are also possible sequelae.

Brucellosis in dogs is caused by ''Brucella canis''. It is a sexually transmitted disease, but can also be spread through contact with aborted fetuses. The most common sign is abortion during the last trimester or stillbirth. Other symptoms include inflammation of the intervertebral disc and eye (uveitis), and inflammation of the testicle ( orchitis) and prostate ( prostatitis) in males.

Tick-borne diseases are common in dogs. Lyme disease, or borreliosis, is caused by ''Borrelia burgdorferi'' and spread by '' Ixodes pacificus'' on the West coast of the United States and by '' I. scapularis'' (deer tick) in the rest of the U.S. Signs and symptoms include fever, joint swelling and pain, lameness, and swelling of the lymph nodes. It has been diagnosed in dogs in all 48 states of the continental U.S. ''Ehrlichia canis'', which causes canine ehrlichiosis, and '' Rickettsia rickettsii'', which causes Rocky Mountain spotted fever, are both spread by the American dog tick, ''Dermacentor variabilis'', and the brown dog tick, '' Rhipicephalus sanguineous''.

Fungal diseases

One of the most common fungal diseases in dogs is ringworm, or dermatophytosis, an infection of the skin, hair, or nails. There are three fungal species that cause ringworm in dogs. About 70 percent of infections are caused by '' Microsporum canis'', 20 percent by ''M. gypseum'', and 10 percent by '' Trichophyton mentagrophytes''. Signs include hair loss and scaling of the skin. Treatment for localized ringworm is not always necessary as the disease is self-limiting, but the clinical course can be shortened by using topical miconazole or clotrimazole. Generalized infections, most commonly seen in immunocompromised dogs, can be treated with oral antifungal drugs such as griseofulvin or itraconazole. Infection can spread to humans.

There are several fungal diseases that are systemic in nature, meaning they are affecting multiple body systems. Blastomycosis, caused by ''Blastomyces'' species including '' Blastomyces dermatitidis'', is a fungal disease that affects both dogs and humans. It is transmitted through the inhalation of fungal spores. It is found mainly in the United States in the Mississippi River and Great Lakes areas. It has also been reported in four Canadian provinces; Saskatchewan, Manitoba, Ontario and Quebec. Signs include weight loss, cough, fever, enlarged lymph nodes, draining skin lesions, eye inflammation with discharge, blindness, and lameness. Because dogs are ten times more likely to become infected from the environment than humans, they are considered to be sentinels for the disease. Treatment requires a minimum 60–90-day course of oral antifungal medication or in severe cases intravenous antifungal injections.

Histoplasmosis, caused by '' Histoplasma capsulatum'', is a disease with a worldwide distribution. In the United States it is mainly found in the Mississippi and Ohio River areas, most commonly in bird and bat feces. Signs include weight loss, cough, fever, enlarged lymph nodes, and gastrointestinal symptoms. Coccidioidomycosis, caused by ''Coccidioides immitis'', is found in arid and semi-arid regions of Central and South America, Mexico, and southwestern United States. Signs include weight loss, fever, cough, enlarged lymph nodes, and lameness.

Parasites

Veterinary parasitology studies both external and internal parasites in animals. External parasites, such as fleas, mites, ticks and mosquitoes can cause skin irritation and are often carriers of other diseases or of internal parasites.

=External parasites

=
*Fleas and ticks of various species can be acquired and brought home by a dog, where they can multiply and attack humans (and vice versa). These two parasites are particularly important to note, now that tick-borne Lyme disease has become endemic throughout a large area, in addition to other similar diseases such as Rocky Mountain spotted fever. Although dogs do not seem to be as susceptible to such diseases as humans, similar rickettsial diseases have been spread by dogs to humans through such mechanisms as a dog killing an infected rabbit, then shaking itself off in the house near enough to its owners to fatally infect most of the family.
*Various mites cause skin problems such as mange.
*Mosquitos
*Lice infestations (pediculosis) cause intense pruritus, scratching, and hair loss. The two species of chewing lice that affect dogs are '' Trichodectes canis'' and ''Heterodoxus spiniger''. The dog sucking louse is ''Linognathus setosus''.

=Internal parasites

=

*Parasites, particularly intestinal worms such as hookworms, tapeworms and roundworms, can be transmitted in a dog's feces. Some tapeworms have fleas as intermediate hosts: the worm egg must be consumed by a flea to hatch, then the infected flea must be ingested (usually by the dog while grooming itself, but occasionally by a human through various means) for the adult worm to establish itself in the intestines. The worm's eggs then pass in the feces, and the cycle begins again. Intestinal worms cause varying degrees of discomfort.
* Heartworm is a dog parasitoid. It is hard to eliminate and can be fatal; prevention, however, is easily achieved using medication. As the name suggests, an infected mosquito injects a larva into the dog's skin, where it migrates to the circulatory system and takes up residence in the pulmonary arteries and heart, growing and reproducing to an alarming degree. The effects on the dog are quite predictable: cardiac failure leading to death. Treatment of an infected dog is difficult, involving an attempt to poison the healthy worm with arsenic compounds without killing the weakened dog, and may not succeed. Prevention is recommended via the use of heartworm prophylactics, which contain a compound that kills the larvae immediately upon infection without harming the dog. Often they are combined with other parasite preventives.
* Hydatidosis is caused by the cestode Echinococcus. It is observed in dogs, wild canids, foxes, etc. Due to its importance as a zoonosis, prevention and treatment is crucial. Preventing hydatidosis is an easier task than treatment. Anthelmintics such as praziquantel may help prevent this condition. Prohibition of the feeding of uncooked offals may be the best prophylactic measure against these tapeworms.

Genetic diseases

Genetic conditions are a problem in some dogs, particularly purebreds. 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.
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. 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. 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. Another class of integumentary malady is hygromas, a swelling typically on or near the elbow joint. Nutrition may also play a role in skin disease, as deficiencies in certain nutrients may result in scaling, redness, oiling, balding, and/or itching of the skin.(See dog skin disorders for specific nutrients that impacts skin)

Physical elements of certain dog breeds also affect susceptibility of individuals to skin problems, such as wrinkled skin or excessive skin folds. For instance, skin-fold dermatitis is a skin infection more prevalent in breeds such as the bulldog, cocker spaniel, and English Springer spaniel.

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), and osteosarcoma (bone cancer).

Certain breeds are more likely to develop particular tumors, larger ones especially. The Golden Retriever is especially susceptible to lymphoma, with a lifetime risk of 1 in 8. Boxers and pugs are prone to multiple mast cell tumors. Scottish terriers have eighteen times the risk of mixed breed dogs to develop transitional cell carcinoma, a type of urinary bladder cancer.

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

Gastric dilatation volvulus, or gastric torsion and bloat, primarily affects breeds with deep, narrow chests, such as Great Danes, St. Bernards, German Shepherds, Standard Poodles and Irish Setters. 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, canine glaucoma, and entropion are seen in dogs. 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. 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

Signs of vestibular disease include head tilt, circling, nystagmus (an abnormal movement of the eyes), and difficulty or inability to stand. These clinical signs are similar to those seen in humans experiencing vertigo. Vestibular disease may have many causes. Elderly dogs are susceptible to an idiopathic (meaning due to unknown causes) form of vestibular disease commonly called "old dog vestibular disease" or idiopathic peripheral vestibular disease. The signs may improve rapidly or take a few days. Less commonly, vestibular signs can also be caused by inner ear disease, a brain tumor, a stroke, or other causes. The major risk with idiopathic peripheral vestibular disease 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. Mitral regurgitation 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, blood vessel constriction, 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 has historically focussed on two types of drugs that address these concerns: diuretics (especially furosemide), which decrease blood volume, and ACE inhibitors, which interrupt the RAAS. Recently, pimobendan – which increases the force with which the heart muscle contracts, and is also a vasodilator – is being more widely used in the treatment of congestive heart failure caused by valvular disease. A major veterinary study, called the QUEST study (QUality of life and Extension of Survival Time), published in September 2008 found that dogs with congestive heart failure receiving pimobendan plus furosemide had significantly better survival outcomes than those receiving benazepril (an ACE inhibitor) plus furosemide. However, ACE inhibitors and pimobendan have different mechanisms of action, and many veterinary cardiologists recommend they be used concurrently. Within the past decade, a new surgical technique has been developed for mitral valve repair that replaces or strengthens the mitral valve chords with polytetrafluoroethylene (PTFE) prostheses and tightens the mitral valve ring to reduce or eliminate regurgitation.

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, Dobermann

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