pets disease

Most bone fractures in dogs and cats are trauma-related. In isolated instances, metabolic diseases, such as nutritional osteodystrophy and bone cancers, can also be underlying causes. A fracture will present itself as a non-weight-bearing lameness, with noticeable swelling and pain in the region of the affected bone. Crepitus, or the grinding feel made by broken ends of bone rubbing together, and an anatomical distortion of the site, such as a shortening of an affected limb, might be seen as well.
Diagnosis of a fracture is based on physical exam findings and radiographic X rays. Treatment depends on the type of fracture and the region involved, and it consists of any combination of cage rest, bandaging or splinting, and surgery to reduce and stabilize the fracture.
Minor fractures involving the pelvis will often heal nicely with cage rest alone, whereas displaced fractures of one or more limbs might require surgical fixation using orthopedic pins, screws, and/or bone plates. In general, uncomplicated fractures usually heal quite readily in dogs and cats.

Both allergies and autoimmune diseases are characterized by an overactive immune system that can irritate or damage its host’s own tissues in response to an antigen invasion within the body. For example, atopic (allergic) dermatitis in dogs and cats results from an overactive immune response to inhaled pollens. Lupus erythematosus and pemphigus are two autoimmune disorders that, aside from causing significant skin lesions, can damage other organs of the body as well. With autoimmune hemolytic anemia, the immune system actually destroys the body’s own red blood cells, leading to anemia. Myasthenia gravis, a disease characterized by profound muscle weakness after only minimal exertion, is also classified as an autoimmune disease. Immunity mediated kidney disease and arthritis can also afflict pets stricken with a genetic predisposition for these disorders. Many cases of hypothyroidism in dogs are caused by an overactive immune system attacking and inactivating the thyroid hormone produced within the body. Finally, in cats, the classic example of an immune system gone awry is feline infectious peritonitis. In this disease, it is not the virus itself but rather the exaggerated immune response to it that actually proves fatal to the cat.
Allergies and most autoimmune reactions can be controlled with corticosteroid medication, which, at high enough dosages, has a suppressive effect on the immune system. However, because these steroids can have significant side effects, such treatments should only be performed under the close, continual supervision of a veterinarian.

As pointed out previously, the immune system is a complicated and delicately balanced system that performs a vital function within the body. If this balance is disrupted, serious trouble can develop.
A suppressed immune system leaves the body wide open to invasion by foreign organisms and cancer cells. This immunosuppressant can occur secondarily to viral infections (such as parvovirus or distemper virus in dogs, and the feline leukemia and feline AIDs viruses in cats), drug therapy (including steroid treatments), severe stress, and disorders of the bone marrow. In addition, pets can actually inherit poorly functioning immune systems. For instance, the incidence of an underactive immune system seems to be higher in Doberman pinschers and Rottweiler than in other breeds.

An antigen is defined as any substance capable of eliciting an immune response. Infectious organisms such as bacteria, foreign matter, and even tumor cells have antigens within their makeup and lining their outer surfaces. Since the body does not recognize such an antigen as one of its own, it mounts an immune response against it to try to eliminate it.
On initial exposure to an antigen, B lymphocytes start to divide and differentiate into their antibody-producing form. It might take up to 7 days before antibody production can be achieved. Even then, production is only moderate, and adequate levels generally last only about 3 weeks. In the meantime, however, other immune components, such as neutrophils, macrophages, and killer cells, are called in to fight off the invader.
If the invader is a tumor cell, foreign body, or an organism that lives and multiplies within body cells (such as viruses do), then the T lymphocytes start to multiply and prepare themselves for battle as well. As with the B lymphocytes, they are specific for each antigen; that is, a lymphocyte that responds to one type of antigen will not respond to any others. As a result, each different antigen that enters the body will stimulate its own group of antagonistic B and T lymphocytes.
Following this initial exposure, the lymphocytes that have been primed to the antigen retain “memory” of the experience. Sent to the front-line defenses, they simply wait for the antigen to show up again. If it ever does, the lymphocytes are ready for it, without the 7day lag time. Antibodies are produced in high levels almost immediately, and the T cells are primed and sent into action with minimal delay.

Special chemicals produced by the cells of the immune system serve to assist them in their protective function. Among those chemicals generated are interferon, interleukins, and complement.
Interferon is a protein that is produced and released by cells that have been invaded by or come in contact with a virus. Released within 2 hours after the cell is invaded, it acts as a messenger to surrounding healthy cells and stimulates the immune system to respond. It even has antitumor effects, preventing tumor cell replication in some instances.
Interleukins are chemicals produced by macrophages that help control and modulate the activity of the T cells during an immune response. Interference with the release of interleukins, which can occur with many viral diseases, can lead to immunosuppressant.
Complement is a special protein produced by the body that attaches itself to the surface of antibodies. When these antibodies bind to a bacterium or infected cell, the complement serves to “burn” a hole in the cell membrane, leading to the cell’s destruction. In some instances, complement doesn’t need the help of antibodies to fulfill this function.

Special cells, called stem cells, located within the bone marrow give rise to all the cells of the immune system. The cells that are produced by these stem cells are referred to as white blood cells. This general category comprises numerous types, each serving distinct functions.
The neutrophils functions to gobble up bacteria that gain entrance into the body. Also assisting in this function are white blood cells called macrophages. These cells usually come after the neutrophils are already engaged. In addition to bacteria, macrophages also have the capability to eat viruses, fungal organisms, and foreign matter.
When a dog or cat is vaccinated, special immune cells called lymphocytes are stimulated. B lymphocytes are responsible for producing actual antibodies in response to the vaccine or foreign organism; T lymphocytes don’t produce antibodies per se, yet they assist the B lymphocytes in doing so, and help modulate the immune response. They also have the ability to attack and kill cells within the body that are cancerous or infected with viruses.
Both B and T lymphocytes are said to possess “memory” that is, they remember the various organisms and invaders that they’re fighting against. That way, if they show up again at a later date, they will be attacked without hesitation. Yet even with memory, this response can become slower and weaker over time if the immune system remains idle. This is why certain vaccination boosters are needed periodically.
Another important lymphocyte of the immune system is called the natural-killer cell, which searches for and destroys tumor cells and cells infected with viruses. Unlike their T-cell counterparts, natural killer cells do not possess memory, yet at the same time, few of them require a previous exposure to a foreign agent to respond effectively.

Without a functioning immune system, our pets would easily fall prey to every hostile organism that came around. Immunity is designed to protect against such infectious invaders and eliminate any foreign matter or cells that somehow gain entrance into the body. Preventing the growth of cancer cells and tumors is also in its job description.
Although the immune system serves a rough and rugged function, a delicate balance does exist as far as its activity is concerned. Stress, poor nutrition, and hormone fluctuations are only some of the many factors which can deleteriously alter this activity, leading to a weakened defense system. As if this weren’t enough, certain viruses, such as the canine parvovirus and the feline leukemia virus, have the ability to suppress the immune system. Such an overwhelming upset of the body’s natural defense mechanisms can only lead to one outcome, and it isn’t good.
This balance can be thrown the other way as well. There are certain disease conditions that can be caused by an overactive, overworking immune system. Allergies are a good example of this. Allergic reactions can even turn deadly if the response is exaggerated enough.
At other times the immune system, in carrying out its duties, will destroy or damage normal healthy tissue in the process. These autoimmune diseases usually result from the body’s inability to turn off the immune response, with disastrous consequences.

Anatomy and Physiology
The immune system itself is a complex network of cells, organs, and special chemicals. No one division overshadows another; each team member relies on the others for support. In this way, they all work in unison toward a common goal.