Arthritis
Arthritis is a group of conditions that affect the health of the bone joints in the body. Arthritic diseases include rheumatoid arthritis and psoriatic arthritis, which are autoimmune diseases; septic arthritis, caused by joint infection; and the more common osteoarthritis, or degenerative joint disease. Arthritis can be caused from strains and injuries caused by repetitive motion, overexertion, and falls. Unlike the autoimmune diseases, osteoarthritis largely affects older pets and results from the degeneration of joint cartilage. Arthritic joints can be sensitive to weather changes. The increased sensitivity is thought to be caused by the affected joints developing extra nerve endings in an attempt to protect the joint from further damage.

Bloat & Gastric Torsion
Breeds with deep chests and narrow waists, such as the Bouvier des Flandres or Doberman Pinscher, for instance, are susceptible to a syndrome of gastric torsion and bloat, where the stomach twists on its supporting ligaments, sealing off the exits, and the contents begin to generate gas pressure which is not only terribly painful (as can be imagined by anyone who has experienced even mild gas pains), but kills large areas of stomach tissue fairly quickly, resulting in a painful death within a very few hours. A similar disease is seen in cattle and horses; and a similar home remedy has sometimes been effective when a veterinarian is not at hand, i.e. puncturing the stomach from outside with a sharp object to relieve the pressure. Obviously, such a remedy must only be attempted as a last resort. Dogs who have experienced such an attack are very susceptible to another which is usually more severe, and this is one case where the most medical intervention usually proves the best choice, normally involving abdominal surgery to tack the dog's stomach down in several places to prevent recurrence.

Canine Distemper
Canine distemper is a disease affecting many types of animals.  Dogs from four months to four years old are particularly susceptible. It prevails most in spring and autumn. The disease generally manifests itself by a dullness of the eye, jaundice (yellowing of eyes), husky cough, shivering, loss of appetite and energy, and occasional fits. While afflicted with canine distemper, dogs should be allowed to run on grass and their diet should be sparse. Canine distemper virus has a tropism for lymphoid, epithelial, and nervous tissues. Therefore, the typical pathologic features of canine distemper include lymphoid depletion, interstitial pneumonia, encephalitis with demyelination, and hyperkeratosis of foot pads . Histologic examination reveals intranuclear and intracytoplasmic eosinophilic inclusion bodies in numerous tissues.  There exist a number of vaccines against canine distemper for dogs and domestic ferrets, which in many jurisdictions are mandatory for pets. The type of vaccine should be approved for the type of animal being inoculated, or else the animal could actually contract the disease from the vaccine. Animals should be quarantined if infected.

Cancer
Cancer is a class of diseases characterized by uncontrolled cell division and the ability of these cells to invade other tissues, either by direct growth into adjacent tissue (invasion) or by migration of cells to distant sites. This unregulated growth is caused by damage to DNA, resulting in mutations to vital genes that control cell division, among other functions. One or more of these mutations, which can be inherited or acquired, can lead to uncontrolled cell division and tumor formation. A tumor refers to any abnormal mass of tissue, but may be either malignant (cancerous) or benign (noncancerous). Only malignant tumors are capable of invading other tissues or metastasizing.  Cancer can cause many different symptoms, depending on the site and character of the malignancy and whether there is metastasis. A definitive diagnosis usually requires the microscopic examination of tissue obtained by biopsy. Once diagnosed, cancer is usually treated with surgery, chemotherapy and/or radiation.

If untreated, most cancers eventually cause death; cancer is one of the leading causes of death in developed countries. Most cancers can be treated and many cured, especially if treatment begins early. Many forms of cancer are associated with environmental factors, which may be avoidable.  Most cancers are initially recognized either because signs or symptoms appear or through screening. Neither of these lead to a definitive diagnosis, which usually requires a biopsy. Some cancers are discovered accidentally during medical evaluation of an unrelated problem. Roughly, cancer symptoms can be divided into three groups.  Local symptoms: unusual lumps or swelling (tumor), hemorrhage (bleeding), pain and/or ulceration. Compression of surrounding tissues may cause symptoms such as jaundice. Symptoms of metastasis (spreading): enlarged lymph nodes, cough and hemoptysis, hepatomegaly (enlarged liver), bone pain, fracture of affected bones and neurological symptoms. Although advanced cancer may cause pain, it is usually not the first symptom. Systemic symptoms: weight loss, poor appetite and cachexia (wasting), excessive sweating, anemia and specific paraneoplastic phenomena, i.e. specific conditions that are due to an active cancer, such as thrombosis or hormonal changes.

Canine Parvovirus (CPV)
Canine Parvovirus (CPV) is a contagious virus affecting dogs. The disease is highly infectious and is spread from dog to dog by physical contact and contact with feces.  There are two forms of CPV: intestinal and cardiac. Cardiac form is less common. It attacks the heart muscle and the dog dies suddenly of a heart attack.  Certain breeds, such as Rottweilers and Dobermanns, have a higher rate of death. Direct contact is not necessary for the disease to spread: shoes, clothing, hair, and so on are all that is needed for the transmission. The disease is extremely hardy and has been found to be present in faeces even after a year including extremely cold temperatures. The only household disinfectant that kills the virus is a mixture of bleach and water, 1 part bleach and 30 parts of water.

Prevention is the only way to ensure that a puppy or dog remains healthy. This disease is extremely virulent and contagious. After the disease starts and symptoms show, the dog normally dies within 48 to 72 hours. It is a painful death. It is extremely important to vaccinate dogs every year against CPV. A dog that successfully recovers from CPV is still contagious for up to 2 months, so the dog must be kept away from other dogs and puppies. Neighbors and family members with dogs should be notified of infected animals so that they can ensure that their dogs are vaccinated and tested.  Dogs that have become infected show symptoms of the illness within 7 to 10 days. The symptoms are lethargy, vomiting, and diarrhea (usually bloody). After a dog is infected, there is no cure. The virus itself does not kill the dog: diarrhea and vomiting result in dehydration and secondary infections set in.  The virus attacks the lymph nodes, intestines, and the bone marrow. Bacteria that normally live in the intestines then leak into the bloodstream and cause septicemia. Due to dehydration, the dog's electrolyte balance is destroyed. Normally 80% of the body is composed of water and, when the body loses 10 to 15% of its water content, death ensues.  Survival rate depends on how quickly it is diagnosed and how aggressive the treatment is. Treatment usually involves costly hospitalization, including IV fluids, antinausea injections, and antibiotics injections. Even with hospitalization, there is no guarantee that the dog will survive.

Diabetes
Diabetes mellitus strikes 1 in 400 cats and a similar number of dogs. Symptoms in dogs and cats are similar to those in humans. Generally, most dogs and about half of cats experience type-1 (insulin-dependent) diabetes, rather than the type-2 that's now becoming common in obese humans. The condition is definitely treatable, and need not shorten the animal's life span or life quality. In cats, prompt effective treatment can even lead to diabetic remission, in which the pancreas can heal. Untreated, the condition leads to blindness in dogs, increasingly weak legs in cats, and eventually malnutrition, ketoacidosis and/or dehydration, and death.

Epilepsy
Epilepsy (often referred to as a seizure disorder) is a chronic neurological condition characterized by recurrent unprovoked seizures.  It is commonly controlled with medication, although surgical methods are used as well. Epileptic seizures are classified both by their patterns of activity in the brain and their effects on behaviour.

In terms of their pattern of activity, seizures may be described as either partial or generalised. Partial seizures only involve a localised part of the brain, whereas generalised seizures involve the entire cortex. The term 'secondary generalisation' may be used to describe a partial seizure that later spreads to the whole of the cortex and becomes generalised. All the causes of epilepsy are not known, but many predisposing factors have been identified, including brain damage resulting from malformations of brain development, head trauma, neurosurgical operations, other penetrating wounds of the brain, brain tumor, high fever, bacterial or viral encephalitis, stroke, intoxication, or acute or inborn disturbances of metabolism. Hereditary or genetic factors also play a role.

Feline Distemper
Feline distemper, is a viral infection affecting cats caused by feline parvovirus, a close relative of canine parvovirus. It is not related to canine distemper. Protection is offered by commercial feline distemper vaccine, which is usually a mixture of vaccines for several different diseases, including panleukopenia.

It is spread from one cat to another, in a variety of ways: any contact with an infected cat's bodily fluids or feces can do the trick, even sharing the same water dish.  The virus primarily attacks the lining of the gastrointestinal tract, causing internal ulceration and, ultimately, total sloughing of the intestinal epithelium. This results in profuse, usually bloody diarrhea, causing severe dehydration, malnutrition, anemia, and often death.  The virus causes a decrease in the cat's white blood cells, thus compromising its immune system. Typically, infection causes a decrease in WBC, hematocrit and platelet counts on a CBC. This is often key in diagnosing panleukopenia.  Symptoms include depression, lethargy, loss of appetite, a high fever, vomiting, diarrhea, and loss of skin elasticity.  If a pregnant cat is exposed during pregnancy, the virus can cause cerebellar hypoplasia in her offspring. This is why administering modified live feline panleukopenia vaccine during pregnancy is discouraged.

Fleas
Flea is the common name for any of the small wingless insects. Fleas are external parasites, living by hematophagy off the blood of mammals and birds. Some well known flea species include; Cat Flea, Dog Flea, Northern Rat Flea, Oriental Rat Flea.  In most cases fleas are just a nuisance to their hosts, but some people and some animals suffer allergic reactions to flea saliva resulting in rashes. Flea bites generally result in the formation of a slightly-raised swollen itching spot with a single puncture point at the center.  However, fleas can transmit disease. One devastating example of this was the bubonic plague, transmitted between rodents and humans. Murine typhus (endemic typhus) fever, and in some cases tapeworms can also be transmitted by fleas.

Heartworm
Heartworm is a parasitic roundworm that is spread from host to host through the bites of mosquitoes. The heartworm affects cats, dogs,  wolves, coyotes, foxes, and some other animals, such as ferrets and even humans. The parasitic worm is called a "heartworm" because the parasite in the final reproductive stage of its life cycle, resides in the heart of its host where it can stay for many years until it kills its host through congestive failure of the heart.

Hip Dysplasia
Hip dysplasia is a congenital disease that, in its more severe form, can eventually cause lameness and painful arthritis of the joints. It is caused by a combination of genetic and environmental factors. It can be found in many animals and, rarely, humans, but is common in many dog breeds, particularly the larger breeds. In the normal anatomy of the hip joint, the thigh bone (femur) joins the hip in the hip joint, specifically the caput ossis femoris. The almost spherical end of the femur articulates with the hip bone acetabulum, a partly cartilaginous mold into which the caput neatly fits. It is important that the weight of the body is carried on the bony part of the acetabulum, not on the cartilage part, because otherwise the caput can glide out of the acetabulum, which is very painful. Such a condition also may lead to maladaptation of the respective bones and poor articulation of the joint.  In dogs, the problem almost always appears by the time the dog is 18 months old. The defect can be anywhere from mild to severely crippling. It can cause severe osteoarthritis eventually.

Hookworm
Hookworm is a parasite that lives in the small intestine of its host, which may be a mammal such as a cat, dog, or human. Two species of hookworms commonly infect humans. The distribution of each species significantly overlaps that of the other. Necator americanus predominates in The Americas and Australia, while only A. duodenale is found in the Middle East, North Africa and southern Europe. Hookworms are thought to infect 800 million people worldwide. The A. braziliense and A. tubaeforme species infect cats, while A. caninum infects dogs. Uncinaria stenocephala infects both dogs and cats. These worms are much smaller than the large roundworm, Ascaris lumbricoides, and the complications of tissue migration and mechanical obstruction so frequently observed with roundworm infestation are less frequent in hookworm infestation. The most significant risk of hookworm infection is anemia secondary to loss of iron and protein into the gut.

Leptospirosis
Leptospirosis is a bacterial disease that affects humans and animals. 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.

Luxating Patella
Luxating Patella, or trick knee, is a condition in which the patella, or kneecap, dislocates or moves out of its normal location. This can be caused by some form of blunt trauma, or may be a congenital defect. Patellar Luxation is a common condition in dogs, particularly small and miniature breeds.  There are several stages in Patellar Luxation, ranging from minor to very serious. The most serious stages require surgery to correct. The surgery involves deepening the groove that the patella sits in.

Mites & Ticks
Mites and ticks are among the most diverse and successful of all the invertebrate groups. They have exploited an incredible array of habitats and because of their small size (some are truly microscopic) most go totally unnoticed. Many live freely in the soil or water, but there is also a vast array of species that live as parasites on plants or animals.  Among the species that attack animals there are members of the Sarcoptic Mange mites, which burrow under the skin. Perhaps the most well known, though, is the house dust mite.

Obesity
Obesity is a condition in which the natural energy reserve of mammals, which is stored in fat tissue, is expanded far beyond usual levels to the point where it impairs health. Obesity in wild animals is relatively rare, but it is common in domestic animals like pig and household pets who may be overfed and underexercised. While cultural and scientific definitions of obesity are subject to change, it is accepted that excessive body weight predisposes to various forms of disease, particularly cardiovascular disease. Interventions, such as weight loss and medication, are frequently recommended to reduce this risk, and many pet owners undertake weight loss regimens for their pets' health as well as aesthetic reasons.

Parasites
Parasites, particularly intestinal worms such as hookworms, tapeworms and roundworms, can be transmitted in a dog's saliva or feces. Some parasites 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 through the intestines and adhere to the nether regions of the dog, and the cycle begins again.

Rabies
Rabies, or Hydrophobia, is a usually fatal disease which can be transmitted to dogs or humans by the bite of an infected mammal, possibly a dog's, cat's, raccoon's, or bat's. Although rodents and similar small mammals can be infected with the disease artificially, they are generally not found infected in the wild; the current hypothesis is that they are not likely to survive any attack that would infect them. Animals with rabies suffer deterioration of the brain and tend to behave bizarrely and often aggressively, increasing the chances that they will bite another animal or a person and transmit the disease. Areas that are rabies-free, (usually islands) such as Britain, Ireland, Australia, and the American state of Hawaii have strict quarantine laws to keep their territories rabies-free. These require long periods of isolation and observation of imported animals, which makes them unattractive places to move with a pet unless the pet is quite young. Areas that are not rabies-free usually require that dogs (and often cats) be vaccinated against rabies. A person or dog bitten by an unknown or unvaccinated dog (or other animal) should always be treated without waiting for symptoms, given the potentially fatal consequences of a rabid biter: there has been only one case of someone surviving rabies when treatment was not begun until after symptoms appeared. The biter should be apprehended if possible, as only autopsy of the brain can determine if it was rabid. This should be a great incentive to dog-owners to vaccinate their dogs even if they feel the risk of their dog contracting rabies is low, since vaccination will eliminate the need for their dog to be euthanized and examined in this fashion should it bite anyone or be suspected of biting anyone, as well as the need for it to be treated for rabies if it is suspected of being bitten.

Roundworms are one of the most common phyla of animals, with over 20,000 different described species. They are ubiquitous in freshwater, marine, and terrestrial environments, where they often outnumber other animals in both individual and species counts, and are found in locations as diverse as Antarctica and oceanic trenches. Further, there are a great many parasitic forms, including pathogens in most plants and animals, humans included.

Salmonella
Salmonella is a bacteria or group of bacteria that can cause illness in humans. The symptoms of Salmonella are usually mild and include diarrhea, abdominal cramps, and fever. Some infections, though, can be quite serious and severe cases can even lead to death. Young children, the elderly, and people with weak immune systems are the most likely to have severe infections. Most cases of Salmonella result from eating contaminated food. Raw eggs and undercooked meat and poultry are common sources as are unwashed vegetables. Food can also become contaminated if someone infected with Salmonella handles it without washing his/her hands. Additionally, Salmonella can be passed in the feces of certain pets. Reptiles are quite likely to shed these bacteria in their feces and a growing number of Salmonella infections each year can be traced to pet reptiles. Most, if not all, reptiles carry Salmonella in their gut and occasionally shed them in their feces, yet the bacteria do not usually cause illness in reptiles. It is virtually impossible to eliminate Salmonella from your pet reptile. People can get Salmonella from reptiles by putting things in their mouth that have been in contact with reptile feces. Simply holding a reptile or being near a reptile will not cause a Salmonella infection, the bacteria must enter the body through a break in the skin or be ingested. Knowing that the risk exists and simple, common sense) are the best defense against contracting reptile-associated salmonellosis.

Tapeworms
Tapeworms live in the digestive tracts of vertebrates as adults and often in the bodies of various animals as juveniles. In a tapeworm infection, adults absorb food predigested by the host, so the worms have no need for a digestive tract or a mouth. Large tapeworms are made almost entirely of reproductive structures with a small "head" for attachment. Symptoms vary widely, depending on the species causing the infection. The largest tapeworms can be 20 m or longer.  Tapeworm awareness is importance to humans because they infect people and livestock. Two important tapeworms are the pork tapeworm, , and the beef tapeworm

Ticks
Ticks are the small wingless external parasites, living by hematophagy on the blood of mammals, birds, and occasionally reptiles and amphibians.

Vertigo
Elderly dogs are susceptible to an unusual form of intense vertigo, the cause of which is unknown; the affected dog is unable to stand up and remains sprawled on the floor, the eyes displaying intense nystagmus, for typically a few days. While terrifying in appearance, owners often fearing that the dog has had a fatal stroke (which is actually uncommon in dogs), the vertigo passes within a few days and by the end of a week the dog is staggering around upright, and within another week there is no evidence that anything at all had happened. The only risk of the disease is that the dog is unable to eat or drink in that condition, and must receive supportive therapy of intravenous fluids and nutrition; a light sedative is usually also administered, as the dog naturally seems terrified during the experience.