Homepage Library Common Diseases in Cats and Dogs

The following are some of the more common diseases and medical conditions found in domesticated cats and dogs in the United States.



Acne is a feline skin disease that primarily affects the chin. Most owners present their cats to the veterinarian for evaluation of a “dirty chin.”
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One of the most common conditions affecting domestic animals is allergy. In the allergic state, the immune system “overreacts” to foreign substances (allergens or antigens) to which it is exposed. Those overreactions are manifested in three ways. The most common is itching of the skin, either localized (one area) or generalized (all over the cat). Another manifestation involves the respiratory system and may result in coughing, sneezing, and/or wheezing. Sometimes, there may be an associated nasal or ocular (eye) discharge. The third manifestation involves the digestive system, resulting in vomiting or diarrhea. The specific response that occurs is related to the type of allergy present.

More About Allergies

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Anal Sac Disease

The anal sacs, or glands, are located on either side of the anus at the nine and three o’clock positions, just under the skin. Connected to the anus by means of a small canal or ducts, anal sacs produce and store a dark, foul-smelling fluid. These are the same types of organs that a skunk uses to scare away its enemies. Although cats and dogs can use these for the same purpose, most cats live in an environment that has no enemies. Because the sacs are rarely emptied, the fluid builds up, solidifies, and becomes an ideal environment in which bacteria can grow.
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Anemia is defined as a reduced number of red blood cells or hemoglobin, or both. It is a clinical sign, not a specific disease. It is a significant finding because red blood cells, or erythrocytes, are needed to transport oxygen to the tissues. When the total numbers of red blood cells are reduced, there can be insufficient oxygen delivery to vital organs.

Red blood cells are produced in the bone marrow, or hollow core of the bones, by specialized cells. Before being released into circulation, the precursor cells must undergo a specific sequence of steps to reach full maturity. Once released by the bone marrow, the red blood cell lives about 60-70 days in cats.
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Bladder Stones (Urolithiasis)

Bladder stones, more correctly called uroliths, are rock-like collections of minerals that form in the urinary bladder. They may occur as a large, single stone or as dozens of stones the size of large grains of sand or pea gravel.

Although the kidneys and urinary bladder are both part of the urinary system, kidney stones are usually unrelated to bladder stones.
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Blastomycosis is a fungal disease caused by the organism Blastomyces dermatitidis. While the first human case was reported in 1898, this disease was not observed in cats until 1961. During the last 20 years, a number of cases of feline blastomycosis have been reported, and we now know that the disease is more common than originally thought.
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Synonymous with the more scientific term gastric dilatation/volvulus (GDV), bloat means that a dog’s stomach distends with gas to the point that the dog goes into shock and may die.
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Cardiomyopathy literally means “disease of the heart muscle.” This is a disease that occurs in cats regardless of breed, sex, or age. There are three distinct forms and a variation of one of them.
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Cat Scratch Disease

Cat scratch disease (CSD), also known as cat scratch fever, is an infectious disease in humans. Evidence is increasing that the cat becomes infected with the causative organism, but it does not appear to produce disease in the cat. Very little is known or understood about the role as of the cat as a reservoir for this disease.
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Cholangiohepatitis is a long and intimidating word that means an inflammation or infection in the gall bladder (cholangitis) and liver (hepatitis). It is a disease that is fairly common in cats of any age.
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Chronic Kidney Disease

Chronic kidney disease is a relatively common disorder in dogs, especially geriatric ones. It occurs when the kidneys are no longer able to perform their normal function of removing waste products from the blood. This is not the same as the inability to make urine. In fact, most dogs with renal disease produce large volumes of urine. The disparity between the large volume of urine produced and declining kidney function are often a source of confusion for owners.
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Chronic Nasal Discharge

When a cat has a discharge from its nose that lasts more than two months, it is considered chronic. Nasal discharge is classified based on the appearance of the draining fluid. The classification is based on the color of the discharge:

  1. Thin and clear like water — serous
  2. Thick and yellow or green in color, similar to pus — purulent
  3. Bloody — sanguineous or hemorrhagic
  4. A combination of any of the above

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Chylothorax is a relatively uncommon disorder in cats in which lymph fluid (chyle) accumulates in the pleural cavity, which lies between the lungs and the inner lining of the chest wall. Normally, only about a teaspoon of clear fluid is present in this space. The purpose of the fluid is to keep the surface of the lungs slippery so that they don’t adhere to the chest wall.
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Coccidiosis is an intestinal infection caused by a one-celled organism called coccidia. Coccidia are not worms; they are microscopic parasites that live within cells of the intestinal lining. Because they live in the intestinal tract and commonly cause diarrhea, they are often confused with worms.
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Collapsed Trachea

The trachea, also known as the windpipe, connects the throat to the lungs. It serves the purpose of directing air into the respiratory tract.

A normal trachea is tubular. It maintains its shape because of a series of rings made of cartilage. These rings do not completely encircle the trachea. Instead, they go from the two o’clock to ten o’clock positions. The remainder of the trachea is composed of a flexible membrane that joins the ends of the cartilage rings.
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Corneal Ulcers

The cornea is the clear, shiny membrane that makes up the surface of the eyeball. It is much like a clear window. To understand the significance of a corneal ulcer, you must first understand how the cornea is constructed.

The cornea is comprised of four layers. The most superficial layer is the epithelium, which is actually comprised of many, very thin layers of cells. Below the epithelium is the stroma. The next deeper layer is called Descemet’s membrane. The deepest layer is the endothelium, which is composed of a single layer of cells. Because all of these layers are clear, it is not possible to see them without special stains and equipment. The cornea must maintain its transparency to ensure clear vision.
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Coronavirus Infection

Canine coronavirus is one of the infectious causes of enteritis, or intestinal inflammation, in puppies and dogs. The first reported outbreaks of this disease came in the 1970s. It is highly contagious between susceptible dogs but, fortunately, most dogs recover without complication. Because of this, it not generally considered a serious canine pathogen (infectious agent).
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Cruciate Ligament Injury

The knee joint of both cats and dogs is one of the weakest joints of the body due to its lack of interlocking of bones. Instead, the two main bones, the femur and tibia, are joined with several ligaments. When severe twisting or excessive extension of the joint occurs, the most common injury is a rupture of the anterior cruciate ligament (ACL). When the ACL is torn, instability occurs that allows the bones to move in an abnormal fashion in relation to one another. When this happens, it is not possible to bear weight on the leg without it collapsing.
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Cryptococcosis a fungal disease caused by the organism Cryptococcus neoformans. While the first human case was reported in 1894, this disease was not observed in the cat until 1951. Since that time, we have learned a great deal about this common feline fungal disease.
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Cushing’s Disease (Hyperadrenocorticism)

Cushing’s disease, also called hyperadrenocorticism, is a disorder in which the adrenal glands overproduce certain hormones. There are two adrenal glands, one on each side of the abdomen just above each kidney.
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The term “cystitis” literally means inflammation of the urinary bladder. Although this term is rather general, there is a common form of cystitis that occurs in cats and, less frequently, in dogs. In cats, cystitis is also known as feline urologic syndrome (FUS) or feline lower urinary tract disease (FLUTD). It affects the bladder (not the kidneys), resulting in the production of bloody urine that contains microscopic crystals. The cat often urinates frequently, usually with the passage of only a few drops of urine. This is often confused with constipation.
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Cytauxzoonosis is a serious, invariably fatal disease of the cat. It occurs when the cat is bitten by a tick; usually the American dog tick (Dermacentor variabilis) is involved. A single tick bite can successfully transmit the organism to the cat. The domestic cat is thought to be an “accidental” host for this parasite. The natural reservoir for the organism is the bobcat; in this species, the organism may survive for long periods of time.
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Degenerative Disk Disease

The spinal cord is one of the most important and most sensitive organs in the body. If it is traumatized, its cells will not regenerate; injuries usually result in permanent damage. Therefore, the spinal cord is protected in a very special fashion: It goes through a bony canal within the spine where it is surrounded by protective bone everywhere except over the disks. This extreme protection reflects its importance and its fragility.
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Dental Disease

Dental disease is a common and often overlooked problem in both cats and dogs. While cavities represent the most common dental disease of humans, cats and dogs are more frequently bothered by tartar buildup on the teeth. Tartar accumulation leads to irritation of the gums around the base of the teeth, ultimately leading to exposure of the roots. Potential outcomes of this tooth-root exposure include gum infections and tooth loss.

You can help prevent dental disease by brushing your pet’s teeth and with regular dental exams.

More About Dental Disease

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There are two forms of diabetes in cats and dogs: diabetes insipidus and diabetes mellitus. Diabetes insipidus is a very rare disorder that results in failure to regulate body water content. The more common type, diabetes mellitus, is a failure of the pancreas to regulate blood sugar. This disease is seen on a fairly regular basis, usually in cats and dogs five years or older. There is a congenital form that occurs in puppies, but this is not common.

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Diarrhea is not a disease but rather a symptom of many different diseases, including, rarely, some fatal ones, such as cancer. Even diarrhea caused by mild illnesses may become fatal if treatment is not begun early enough to prevent severe fluid and nutrient losses. Many mild cases of diarrhea can be resolved quickly with simple treatments.
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Dilated Cardiomyopathy

The heart has four chambers: two upper chambers (atria) and two lower (ventricles). In addition to the upper and lower chambers, the heart also has a right and a left side.

Blood flows from the body into the right atrium. It is stored there for a few seconds, then pumped into the right ventricle. The right ventricle pumps blood into the lungs, where it receives oxygen. It flows from the lungs into the left atrium and is held there for a few seconds before going into the left ventricle. The left ventricle contains the largest muscle of the heart so the blood can be pumped out to all parts of the body.

Dilated cardiomyopathy (DCM) means that the heart muscle (myocardium) becomes much thinner than normal. In particular, the thick muscle wall of the left ventricle is affected. The pressure of the blood inside the heart allows this thinned wall to begin to stretch, resulting in a much larger left ventricular chamber. Therefore, the two characteristics of dilated cardiomyopathy are a heart wall that is much thinner than normal and a chamber that is much larger than normal. See also: mitral valve disease.
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Canine distemper virus (CDV) is a contagious disease that affects the respiratory tract, the gastrointestinal tract, and the central nervous system, including the brain and spinal cord. In addition to dogs, CDV infects other species as well such as coyotes, foxes, raccoons, ferrets, minks, and skunks. Young dogs are more susceptible to the virus than more mature dogs. For dogs that become affected with CDV but survive, longstanding immunity usually results, but this immunity typically declines with time.

More About Canine Distemper

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Ear Disease & Infections

Otitis externa, an infection of the external ear canal (outer ear) by bacteria or yeast, is one of the most common types of infections seen in dogs and, less commonly, cats. When the middle and inner ear are involved, these are described as otitis media and otitis interna, respectively. Some breeds, such as cockerspaniels and miniature poodles, seem more prone to ear infections, but they may occur in any breed.

More About Ear Disease & Infections

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An infectious canine disease, ehrlichiosis first gained attention when military dogs returning from Vietnam during the 1970s were found to be infected. The disease seems to be particularly severe in German shepherds and Doberman Pinschers.
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Eosinophilic Granuloma Complex

The eosinophilic granuloma complex is a group of diseases that appear to be related. The causes are distinct lesions on the skin that respond to the same treatment; this is one of the reasons that they are grouped together as a “complex.” The name is somewhat misleading because not all variations of the lesions contain eosinophils.

Eosinophils are a type of white blood cells, which are part of the body’s immune system. Their numbers increase in certain diseases, including allergies and parasites. They are also found in high numbers in a few other diseases but are typically not related to cancer.
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Feline Elimination Behavior Problems

Buspirone (trade name BuSpar) is a drug used by physicians to treat anxiety disorders in humans. Clinical trials with the drug have demonstrated its effectiveness in treating cats with elimination behavior problems (urine spraying). Although its success rate is not 100%, it has been shown to be useful in many cats. One study showed about a 75% reduction in urine spraying in half of the cats studied.

Buspirone is not labeled as a veterinary-approved product. Although tested in a large number of cats, it is not approved by the FDA for this purpose. Significant side effects have not been observed but are always possible. Any abnormal behavior in a cat taking the drug should be reported.
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Feline Immunodeficiency Virus

The feline immunodeficiency virus (FIV), often called feline AIDS, is an infectious disease likened to the human AIDS virus due to their similarities. Fortunately, most viruses are species-specific, as is the case with both human AIDS and FIV.
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Feline Infectious Anemia (Hemobartonellosis)

Feline infectious anemia (FIA) is a feline blood disease caused by a microscopic parasite called Hemobartonella felis. Because of the organism’s name, this disease is also sometimes called hemobartonellosis. The organism attaches to the surface of the red blood cells, where its presence is eventually detected by the immune system, at which point it attempts to eliminate it by destroying the red blood cells. With destruction of a large number of red cells, anemia may result.
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Feline Infectious Peritonitis

Feline infectious peritonitis (FIP) is a progressive, almost always fatal, viral disease in domestic cats. It affects some exotic cats, with the cheetah being particularly susceptible. It does not affect non-feline species, such as dogs.
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Feline Leukemia Virus Diseases

Feline leukemia virus infection was, until recently, the most common fatal disease in cats. Because we can now protect cats with a leukemia vaccine, we are seeing fewer cases of the disease. However, it still remains a major cause of death in cats.

Leukemia means cancer of the white blood cells. This was the first disease associated with the feline leukemia virus (FeLV) and, thus, the source of its name. We often use the term “leukemia” rather loosely to include all of the diseases associated with the virus, even though most are not cancers of the blood. This virus causes many other fatal diseases, in addition to leukemia.
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Successful flea control has two aspects: on your pet and in their environment. Since cats and dogs share the same fleas, the presence of a cat in your dog’s environment, or vice versa, can make flea control much more difficult.
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Fight-Wound Infections

Cats are very territorial animals and will fight with other cats to establish or defend territory. As a result, fight wounds are common in cats. These wounds frequently result in an infection that can be quite debilitating, especially if left untreated.
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Giardiasis is an intestinal infection in humans and and animals that is caused by a protozoal parasite called Giardia intestinalis, widely known as the source of “traveler’s diarrhea.” These single-celled parasites are not to be confused with common intestinal parasites such as roundworms, hookworms, and tapeworms. Fortunately, even though the prevalence rate is high in cats and dogs, clinical disease is less common.
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Heartworms (Dirofilaria immitis) are nine- to eleven-inch worms that live in a dog or cat’s heart or in the arteries going to the lungs (pulmonary arteries). Although they occur commonly in dogs, most people do not consider them a problem in cats. However, recent studies of cats with heart and respiratory diseases have found an incidence of heartworms that is far greater than previously thought.
Heartworm disease (dirofilariasis) is a serious and potentially fatal disease in dogs. One dog may have as many as 300 worms.
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Hematoma of the Ear (Aural Hematoma)

An aural (ear) hematoma is a collection of blood, serum, or clotted blood within the earflap (pinna). When present, the pinna will be very thick. The swelling may involve the entire pinna or only one area.

When something irritates the ear canal, the animal responds by scratching or shaking the head. Excessive shaking causes blood vessels to break, resulting in bleeding.
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Hemorrhagic Gastroenteritis

Hemorrhagic gastroenteritis (HGE) is a fairly common disorder of dogs that is characterized by the sudden development of vomiting and/or diarrhea. The vomitus and the diarrhea may contain variable amounts of bright, red blood or dark, digested blood.
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Hepatic Lipidosis (Fatty Liver Syndrome)

Hepatic lipidosis, also known as fatty liver syndrome (FLS), is one of the most common liver disorders in cats. It is also seen in horses, dairy cows, and, rarely, in very young puppies. In dogs, however, it is not thought to cause a significant illness.
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Hip Dysplasia

Defined as a deformity of the hip (coxofemoral) joint that occurs during the growth period, hip dysplasia (HD) is a hereditary condition that creates a poorly fitting hip joint. As the dog walks on the joint, arthritis eventually develops, causing pain. The degree of lameness that occurs is usually dependent upon the extent of arthritic changes in the hip joint.
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Histoplasmosis is a multiple-organ (systemic) fungal disease caused by the organism Histoplasma capsulatum. The first human case was reported in 1906, but it was not reported in cats until 1949.
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Found in both cats and dogs, hookworms are intestinal parasites that get their name from the hook-like mouthparts they use to anchor to the lining of the intestinal wall. They are only about 1/8-inch (1-2 mm) long and so small in diameter that they are barely visible to the unaided eye.

The scientific names for the most common feline hookworms are Ancylostoma tubaeforme and Ancylostoma braziliense. Occasionally, cats will also become infected with the dog hookworm, Ancylostoma caninum.
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Hypertension is the term for high blood pressure. In humans, hypertension is related to several factors, including a stressful lifestyle. Although not all the causes of feline hypertension have been identified, stress does not appear to play a role in the development of this disorder in cats. However, kidney disease and thyroid disease are known to cause feline hypertension.
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Composed of two lobes, one on each side of the windpipe (trachea), the thyroid gland plays a key role in regulating the body’s rate of metabolism. The disorder characterized by the overproduction of thyroid hormone and a subsequent increase in the metabolic rate. This is a fairly common disease in older cats. Although the thyroid gland enlarges, it is usually a nonmalignant (benign) change. Less than 2% of hyperthyroid cases involve a malignancy. If the case is severe enough, a thyroidectomy may be required.

Many organs are affected by this disease, including the heart. The heart is stimulated to pump faster and more forcefully; eventually, the heart enlarges to meet these increase demands for blood flow. The increased pumping pressure leads to a greater output of blood and high blood pressure. About 80% of cats with hyperthyroidism have high blood pressure. See also: hypothyroidism.
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The opposite of hyperthyroidism, hypothyroidism is when the thyroid gland is less functional than normal, causing metabolism to slow down.
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Icterus, also known as jaundice or yellow jaundice, is a condition in which a yellow pigment is found in the blood and tissues. It is most easily seen in the gums, the white part of the eyes (sclerae) and ear flaps (pinnae). However, if these areas normally have a dark color, icterus will probably not be seen.
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Infectious Canine Hepatitis

The word “hepatitis” is a nonspecific medical term describing any inflammatory process of the liver. A number of different diseases can cause hepatitis, such as infectious canine hepatitis (ICH). This viral disease was first recognized as unique to dogs in 1947.

More About Infectious Canine Hepatitis
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Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a relatively common medical problem in cats and dogs. It is not a specific disease; rather, the term IBD represents several processes that are manifested as inflammation of the bowel. It may involve only the small intestine, large intestine, or stomach; in some cases, all parts of the gastrointestinal tract are affected.
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Kennel Cough

Kennel cough (canine infectious tracheobronchitis) is a respiratory disorder that is highly contagious between dogs. A number of different infectious agents may be involved with the disease, which is characterized by bouts of nonproductive (dry) coughing lasting from days to even weeks.

More About Kennel Cough

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Kidney Disease

Chronic kidney disease is a relatively common disorder in cats and dogs, especially geriatric ones. Kidney (renal) insufficiency or failure occurs when the kidneys are no longer able to perform their normal function of removing waste products from the blood. The former is the early stage of the latter.

Kidney failure is not the same as the inability to make urine. In fact, most animals with kidney failure produce large volumes of urine in an attempt to remove the waste products that have accumulated in the blood. This apparent contradiction between the large volume of urine produced and declining kidney function is often a source of confusion for owners.
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Leptospirosis is a relatively complex infectious disease in dogs, although it can affect almost all species of warm-blooded animals, including humans.

Recognition of the disease is sometimes difficult because clinical signs vary depending upon the particular strain (serovar) of the Leptospira organism caused the infection. At least ten different serovars are known to infect dogs. Most commercial vaccines contain antigens (proteins) that stimulate immunity against the icterohemorrhagiae and canicola serovars. The incidence of disease caused by these two serovars has decreased thanks to vaccines; however, other serovars are becoming more common in the animal population.
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Lick Granulomas

A lick granuloma is an open sore on the skin caused by and perpetuated by constant licking. It is generally located on one of the legs, especially near the wrist (carpus) joint. Typically, the hair is licked off and the area is either raw and weeping or thickened and scar-like.

Lick granulomas usually begin with an itching or tingling sensation on the leg. The dog responds by licking, which may further increase the itching or tingling. Very shortly, a viscious cycle develops, creating a habit much like a child sucking its thumb. Even if the problem that initiated the itching or tingling sensation is gone, the habit of licking continues.
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Lumbosacral Stenosis

This disease occurs at the lumbosacral junction — “lumbo” referring to the the bones in the lower part of the spinal column (lumbar vertebrae) and “sacral” to the the part of the spine that joins the lumbar spine and the pelvis (sacrum). Changes that occur in the vertebrae, supporting ligaments, or adjacent disks can all contribute to this pathologic narrowing of the spinal cord canal.
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Luxating Patella (Dislocated Kneecap)

The kneecap (patella) is normally located in the center of the knee joint, but it can become out of place or dislocated (luxated).
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Lyme Disease

Lyme disease is caused by a type of bacterium (spirochete) called borrelia that is transmitted through tick bites. Once in the blood stream, it is carried to many parts of the body. It is especially likely to localize in joints. It was first thought that only a few types of ticks could transmit this disease, but now it appears that several common species may be involved.

Lyme disease is named after the city in which it was first discovered, Old Lyme, Connecticut. Thus, the correct name is “Lyme disease,” not “Lyme’s disease.” Although humans can get Lyme disease, they do not get it from their pet bur rather a tick bite.

Clinical Signs: Many dogs affected with Lyme disease present with generalized pain (often referred to as “walking on egg shells”) and loss of appetite. Often, these cases also have high fevers. Painful lameness also appears suddenly and may shift from one leg to another. If left untreated, these symptoms may eventually disappear only to recur weeks or months later.

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Mange is a parasitic skin disease caused by microscopic mites. Two different types of mange mites are significant in dogs, one which lives just under the surface of the skin (sarcoptic mange) and the other in the hair follicles (demodectic mange). Although both types of mites share some similar characteristics, it is important not to confuse the two types of mange because they have different causes, treatments, and prognoses.
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The colon is a tubular, muscular structure, that comprises the end of the intestinal tract and is continuous with the rectum. The colon has several functions, such as absorption of water, storage of feces, and defecation. When the muscles in the wall of the colon are stimulated to contract by nerves from the spinal cord, fecal material is pushed out of the body. Megacolon is a condition of colonic dilation and is a fairly common problem in cats.
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Mitral Valve Disease

Each side of the heart has a valve to keep blood from going backward from the ventricles to the atria. The valve between the left atrium and left ventricle is called the mitral valve. Because of the very large pressures created when the left ventricle contracts and the eventual process of “wearing out,” the mitral valve becomes leaky in many dogs.

Because this is a progressive disease, dogs are assigned to one of four stages based on clinical signs, historical findings, and x-ray findings. Stage 1 is the earliest stage of mitral valvular disease, while stage 4, the final stage, is the presence of life-threatening heart failure. See also: dilated cardiomyopathy.
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Obstructive Lung Disease (Asthma and Bronchitis)

Obstructive and allergic lung diseases affect many cats and are sometimes called asthma, bronchitis, or bronchial asthma. Unfortunately, these diseases are not easily classified and probably represent a variety of lung disorders. They do share a common finding of over-reactive (hyper-responsive) airways.

When a cat’s airway is sensitive to certain stimuli, exposure to these agents leads to narrowing of the airways. The inciting agents are usually direct irritants to the airways or things that provoke an allergic response in the respiratory tract. Regardless of the cause, the end-result is the same: muscle spasms in the breathing tubes (bronchi), buildup of mucus, and accumulation of cellular material. In particular, the inability to clear the bronchi of this material leaves the cat susceptible to secondary infections.
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Located on the right side of the abdomen near the ribs, the pancreas produces digestive enzymes and hormones, such as insulin. Pancreatitis is a disorder of the pancreas that involves an intense inflammatory process. Although pancreatitis occurs less commonly in cats than dogs, recent research efforts have demonstrated that it occurs more commonly than previously believed.

There are two main forms of sudden onset (acute) pancreatitis: the mild, edematous form and the more severe, hemorrhagic form. A few dogs that recover from an acute episode of pancreatitis may continue to have recurrent bouts of the acute disease, known as chronic, relapsing pancreatitis. The associated inflammation allows digestive enzymes to spill into the abdominal cavity, which may result in secondary damage to surrounding organs, such as the liver, bile ducts, gall bladder, and intestines.
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Canine parvovirus (CPV, or parvo) is a relatively new disease that first struck the canine population in 1978. The classic signs are vomiting and bloody diarrhea. Because of the severity of the disease and its rapid spread through the canine population, CPV has aroused a great deal of public interest. The virus that causes it is very similar to feline distemper, and the two diseases are almost identical, leading to speculation that the canine virus is a mutation of the feline virus; however, that has never been proven.

The virus has a selective effect on the most rapidly dividing cells of the body. For this reason, the lining of the small intestine and the cells of the bone marrow are most severely affected.
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Prostate Disease

The prostate (commonly mispronounced as “prostrate”) is a gland located near the neck of the urinary bladder of male dogs. The urethra passes through it shortly after leaving the bladder. The purpose of the prostate is to produce some of the fluids found in normal canine semen.
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In its simplest terms, pyometra is an infection in the uterus. However, most cases of pyometra are much more difficult to manage than a routine infection.
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Pyothorax is a bacterial infection that develops in the chest cavity (pleural space), located between the lungs and the chest wall. The presence of bacteria in the chest cavity causes white blood cells and fluid to migrate into the pleural space; eventually, pus begins to accumulate. Fluid in the chest cavity causes a mechanical problem in that it limits the amount of room available for the lungs to expand. As fluid accumulates, the animal tries to compensate by breathing more rapidly. As more and more fluid builds up, the animal is forced to take very shallow breaths. Pain associated with inflammation in the pleural space (pleuritis) may also contribute to shallow breathing. In addition to respiratory difficulties, the infection in the chest releases toxins into the blood stream, which is a further stress on the cat.
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Rabies is a viral disease that may infect any warm-blooded animal. Regardless of the initial site of virus introduction into the animal, the virus eventually invades the central nervous system. With rare exception, it is a uniformly fatal disease.
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Ringworm (dermatophytosis) is a skin disease caused by a fungus. Because the lesions are often circular, ringworm was once thought to be caused by a worm curling up in the tissue, but this has been proven to be false.

There are four species of fungi that can cause ringworm in cats; however, it is most often caused by the organism called Microsporum canis, which is so well adapted to cats that up to 20% of cats are thought to be asymptomatic carriers, meaning they have the organism but show no outward signs.

The fungi live in hair follicles and cause the hair shafts to break off at the skin line. This usually results in round patches of hair loss. As the fungus multiplies, the lesions may become irregularly shaped and spread over the body. Ringworm is contagious and can also infect humans.
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Roundworms are the most common intestinal parasite in cats and are also common in dogs. The rate of roundworm infection (ascariasis) in kittens is thought to approach 100% and can cause illness and even death. As their name implies, these are large-bodied round worms, averaging about 3-6 inches (8-15 cm) in length. In contrast to the behavior of the hookworm, the roundworm does not attach to the intestinal wall but rather swims within the food in the intestine.
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Seizures are one of the most frequently seen neurological problems in both dogs and cats. A seizure, also known as a convulsion or fit, represents a period of abnormal brain wave activity that leads to a variety of clinical signs.
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Staph Dermatitis

Staph is a commonly used abbreviation for Staphylococcus, a group of bacteria commonly found on the skin. Dermatitis is a term that means that the skin is inflamed.

Staph is a normal resident of the skin of animals and humans; however, it is considered an opportunist. As long as the skin is healthy, staph is dormant. But once the skin is irritated, staph can invade the area and multiply rapidly.
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Like hookworms and roundworms, tapeworms are intestinal parasites common in cats and dogs. There are several types, but the most common is Dipylidium caninum, which uses its hook-like mouthparts to anchor to the wall of the small intestine. Eventually, adult tapeworms may reach eight inches (20 cm) in length. The adult worm is made up of many small segments about 1/8-inch (3 mm) long. As the tail end of the worm matures, the terminal segments break off and pass into the stool. Occasionally, the mobile segments can be seen crawling near the anus or on the surface of a fresh bowel movement. These segments look like grains of rice and contain tapeworm eggs, which are released into the environment when the segment dries. The dried segments are small (about 1/16 inch, or 2 mm), hard, and golden in color and can sometimes be seen stuck to the hair around the anus.
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Plaque is a gummy substance that forms on the teeth within a few hours after a meal. Within 24 hours, plaque hardens into tartar.

Tartar is harmful in two ways. First, it serves as a place where bacteria can reside and multiply in the mouth. There is substantial scientific evidence that bacteria from tartar enter the blood stream and are deposited in various organs. Heart and kidney disease can result. Second, tartar builds up at the gum line. As the tartar deposit gets larger, it pushes the gums away from the roots of the teeth. Eventually, the teeth loosen and fall out.

You can help prevent tartar buildup by brushing your pet’s teeth and with regular dental exams.
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Since dogs have tonsils, it is possible for them to have tonsillitis. There are two of them, located in the back of the throat. When they are normal, they are not easily seen because they reside in pouches (crypts). Like lymph nodes, their job is to fight infection. When they are doing this, they often become infected themselves and will enlarge.
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An infectious disease caused by the one-celled parasite Toxoplasma gondii, toxoplasmosis is prevalent in cats throughout the world, although other species can become infected. The cat is unique in that it is the definitive host of the parasite, meaning that the organism must pass through the cat to complete all stages of its life cycle.
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Upper Respiratory Infections

Cats may become infected with respiratory viruses that resemble the common cold in humans. The infection could occur in the nose, throat, and trachea (upper respiratory tract) or lungs (lower respiratory tract).
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Vomiting is not a specific disease but rather a common symptom of a number of different diseases. In general, a veterinarian must decide whether the cause of vomiting is more likely to fall into a particular category of causes:

    1. A disorder outside the gastrointestinal tract (systemic disease). Examples of systemic diseases include liver failure, kidney failure, thyroid disease, heartworms, and diabetes mellitus.
    2. A disorder within the gastrointestinal tract or abdomen. Examples of these disorders include intestinal parasites, dietary indiscretion, pancreatitis, inflammatory diseases of the stomach and/or intestinal tract, and cancer.

A common problem in dogs, chronic vomiting may be related to relatively minor causes, such as chronic swallowing of hair, or it may be due to much more serious diseases.
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Von Willebrand’s Disease

Von Willebrand’s disease (VWD) is the most common inherited bleeding disorder of both man and animals. It is caused by a deficiency in the amount of a protein needed to help platelets (a blood cell used in clotting) seal broken blood vessels. The deficient protein is called von Willebrand factor antigen.
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Whipworms are intestinal parasites that cause signs related to intestinal irritation. Infection with whipworms can be significant because they are one of the more pathogenic intestinal parasites found in dogs.

Whipworms are small, about 1/4-inch (60 mm) long and have a characteristic “whip” or “lash” at one end. After the worm burrows into the intestine, it is this whip that causes damage to the lining of the bowel. The tip of the whip is able to slash and shred tissue. The worm then feeds on the blood and damaged lining of the intestine.
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