Реферат: Animal Diseases Essay Research Paper Diseases of

Animal Diseases Essay, Research Paper

Diseases of Animals, are disorders that influence an animal’s health and ability to function. Animal diseases are a great concern to humans for several reasons. They can reduce the productivity of animals used to produce food, such as hens and dairy cows. Animals that are raised for food, such as pigs and beef cattle, that become ill may affect the economy of many industries. Some animal diseases can be transmitted to humans, and control of these types of diseases, known as zoonoses, is vital to public health.

Animal diseases are identified as infectious and non infectious. Infectious diseases are caused by an agent, such as bacteria or a virus, while non infectious diseases are caused by factors such as dieting, environment, injury, and heredity. Sometimes the cause of a disease is unknown. An animal may also experience more than one disease at the same time.

To identify a disease, a veterinarian first determines the animals species, breed, age, and sex. The information helps him identify a disease because some diseases are more prevalent in certain species, or a disease may preferably affect one sex or age group. The vet then gathers a complete history of the animal and its problem. This history includes the symptoms the animal is displaying and when they first appeared, as well as whether the animal has been exposed to something new in its surroundings or to other animals. The vet gives the animal a physical examination, which may include measuring its body temperature, listening to its heart, checking its pulse, and feeling its abdomen and lymph nodes. The vet then creates a list of possible diseases that may be making the animal sick. The list may be narrowed by running a few diagnostic tests such as X rays, electrocardiograms, blood analyzes, and bacterial or fungal cultures. Once the disease is identified, the doctor develops a treatment plan for the animal.


Many microscopic organisms exist in enormous amounts within animal bodies. For example, the multi chambered stomach of a cow contains bacteria that helps the animal digest its food. But many other microscopic organisms, known as pathogens, cause diseases in animals. Pathogens include bacteria, viruses, fungi and parasites,. Pathogens are easily spread by an animal consuming food or drinking something that has been contaminated with infected material, for example. If the ground is contaminated by Salmonella bacteria, infection can travel from barn to barn on the soles of a farmer’s boots. Or an animal may be exposed while walking across contaminated ground. Some diseases are transmitted by biting insects; others are spread by sexual contact.

In addition to reducing the productivity fertility of livestock, some infectious diseases pose a danger to humans. Most cases are transmitted from animals that have close contact with humans, such as pets, farm animals, or rats. As the human population grows and expands into wilderness territories, humans are coming into closer contact with other animals that carry pathogens dangerous to humans. Some of these pathogens are carried by insects, like the case of the yellow fever, which is spread from monkeys to humans via mosquito bites. Some hemorrhagic fevers, such as that caused by Ebola virus, are recognized as zoonoses, but the exact route from animal to human is still unknown.


Salmonellosis is a disease caused by the Salmonella bacteria, characterized by severe diarrhea. In its many forms, it is one of the major disease of wild and domestic animals, birds, and reptiles, along with humans. Salmonella bacteria usually enter the body through the mouth, most commonly along with food or water contaminated by infected filth. Transmission also may occur through direct contact with an infected animal. In addition, salmonella bacteria can be spread by contact with objects, such as bowls and cutting boards, that have been contaminated by infected animal products, such as eggs or meat.

Leptospirosis, is caused by spiral Leptospira bacteria, and affects cattle, dogs, pigs, sheep, goats, and humans. Ponds, lakes, and other bodies of water are common sources of leptospirosis, and rodents may carry the infection. This infection causes kidney disease and destruction of red blood cells with potential anemia; it may also cause abortion.

Tuberculosis is a chronic disease of animals and humans, caused by bacteria of the genus Mycobacterium and transmitted by inhalation of droplets from an infected animal’s cough or sneeze, or by a wound. TB infection causes lesions called tubercles to develop in certain tissues, such as the lung or liver. Symptoms include fever, emaciation, and progressive loss of strength.


Feline leukemia is caused by the feline leukemia virus. Often fatal, it can seriously impair the immune system and, in some cases cause the growth of life-threatening tumors. Spread from direct contact with an infected cat, symptoms of the disease include lethargy, weight loss, anemia, and fever. A cat may not appear ill until years after exposure.

Foot and mouth disease is caused by a virus found in the saliva of cattle, pigs, and other hoofed animals. Highly contagious, it is spread from direct contact with an infected animal. It may also spread in milk or in garbage that contains contaminated meat. Typical symptoms include blisters that appear on the mouth and feet; animals may become lame when their hooves degenerate.

Canine distemper is a highly contagious disease caused by the paramyxovirus, which is transmitted in discharges from the nose and eyes. Symptoms begin with fever, malaise, and nasal and ocular discharges and may progress to convulsions and other nervous system disorders. Parvo viruses affect dogs and in some cases cattle, pigs, and humans. Usually fatal if left untreated, canine parvo virus causes inflammation of the intestines, producing diarrhea, vomiting, fever, and loss of appetite.


A fungal infection typically develops slowly and recurs more frequently than a bacterial infection. Histoplasmosis, characterized by a chronic cough and diarrhea, is contracted by inhaling the Histoplama capsulatum fungus, which grows in soil. In the Central United States Histoplasmosis is the most widespread fungal disease diagnosed in dogs, although it also affects other animals. Ringworm, a common skin disease of many species, causes circular patches of hair loss and scaly, reddened skin. It readily spreads by direct contact with an infected animal.

Yeast is another type of fungus, that grows in warm and moist places, such as the ear canals of dogs. It may cause otitis externa, an infection of the outer ear. The yeast Candida albicans is commonly found in the intestinal tract of birds and other animals. It may be the primary cause of disease, or it may be a secondary invader in an animal already sick with another infection.


Diseases caused by parasites are widespread in domestic animals and wildlife. Parasites may be internal or external. Internal parasites include Coccidia, a microscopic protozoal organism that causes diarrhea and extreme weight loss in many young animals.

Other internal parasites include the roundworm, tapeworm, and fluke. Larval roundworms can cause considerable damage to lungs and other organs in some animals. For instance, Capillaria worms may attack the lining of the digestive tract of chickens and turkeys; they parasitisize the respiratory and urinary tracts of dogs. Adults of the heartworm Dirofilaria immitis, another roundworm, live in the heart of dogs and produce microscopic larval stages, which swim in the blood. Symptoms of heartworm disease include coughing, fatigue, and weight loss. If left untreated, an animal may experience heart failure. Tapeworms may have very damaging Laval stages. In echinococcosis, the larval tapeworm may from large cysts in liver, lungs, and other organs of humans and animals.

Flukes may directly damage the liver, lungs, or intestines, or they may act as carriers of other disease agents, as in the case of salmon poisoning of dogs in which the fluke, encysted in the body of a salmon, carries a virulent rickettsial agent.

External parasites live or feed on the surface of the animal’s body. This group includes insects, such as mosquitoes, gnats, some flies, fleas, and some lice. Great damage to the meat and hides of cattle is caused by larval flies such as the ox warble, which migrates through the tissues and, after boring breathing through the skin, leaves the body to reproduce.


Newly identified protein particles called prions have been found in the brains of animals that have died from diseases such as scraple and mad cow disease. Scientists believe that prions attach to normal proteins in the brain. Once attached, the prions cause the normal proteins to change into an abnormal shape, leading to progressive destruction of brain cells and death. Prion diseases are thought to spread by means of feed supplements derived from infected animals. In recent years, public health officials have been concerned about the possibility that prion diseases may be transmitted to humans. This can happen when people eat contaminated beef or organs, causing them to contract such rare neurological diseases as Creutzfeldt-Jakob disease.


Controlling the spread of infectious animal diseases starts with isolating, animals with threatening infections, such as salmonella, to prevent further spreading. Many bacterial diseases can be treated with a variety of antibiotics, such as penicillin. But as with all disease, prevention is more important than treatment, and a major activity for vets is immunization of animals. Immunization commonly involves an injection of a weakened or killed pathogen for a specific type of disease that encourages the immune system to fight off infection. Many infectious diseases, including rabies, canine distemper, feline leukemia, anthrax and brucellosis, can be prevented by immunization. In the case of very severe outbreaks of infectious diseases, public health officials may work with animal owners to destroy large groups of animals.


Many animal diseases are caused by noninfectious factors such as an animal’s environment, genetics, and nutrition. Heatstroke, for example, occurs when an animal is forced to endure high temperatures without access to water, or suitable shade. A common scene involves an animal that has been locked inside a car without air conditioning during hot weather. On the other hand, extreme cold can lead to hypothermia or frostbite. Other environmental hazards include the vast array of products humans use to eliminate pests and weeds from homes, farms and gardens. For example, rodenticide, poison used to kill rats and mice, can cause fatal internal hemorrhaging in any animal that ingests this toxic substance. Automobile antifreeze is another well known poison. Its sweet taste appeals to some animals, such as cats and dogs, but consuming only a small amount can result in death. Many plant species are also toxic to animals. Some, such as pokeweed and yew, commonly grow in yards.

Poor feeding can lead to diseases such as nutritional secondary hyperparathyroidism, a condition involving the muscles and bones of dogs that is associated with an all meat diet. Large, growing puppies that consume too many calories and too much calcium can develop hypertrophic osteodystrophy, a disease resulting in lameness. Cats need sufficient amounts of an essential amino acid called taurine in their diets. Without it, they may develop eye problems. Not enough iodine intake can cause a goiter, or enlargement of the thyroid gland, in cows horses, an other animals.

Trauma is a leading cause of injury and premature death in animals, especially pets that are allowed to roam free outdoors. Many animals are hit by cars or bitten by other animals. Farm animals may be attacked by predators, or they may harm themselves on sharp fencing or discarded nails. Untreated wounds can become infected and cause permanent damage.

Hip dysplasia, is a painful skeletal condition that is a noninfectious disease caused by heredity. Certain defects of the heart of palate, the roof of the mouth, may also be inherited.

An animal’s immune system is designed to detect and eliminate invading organisms. Occasionally, however, it behaves as though the animal’s own body were the attacker, and it destroys healthy tissue. Diseases caused by this response, known as autoimmune diseases, include pemphigus fallacious, a skin disease of dogs, cats, and horses; and arthritis. In the autoimmune disease hemolytic amenia, the animal’s own red blood cells are destroyed by its immune system.

Cancer exists in all animals. It its classified as either benign- that is, relatively non aggressive and unlikely to return after treatment; or as malignant- aggressive and likely to spread. Any organ or system can be affected, either directly or through metastasis- when cancer cells from one part of the body spread to other areas of the body. Some forms of cancer are more widespread in animals of a particular breed, age, or sex, and ever individuals of a specific color. For example, cancer of the mammary gland occurs more often in female animals, while melanoma, or skin cancer, is the most frequent tumor of elderly gray horses, and lymphosarcomas, tumors of the lymph nodes, are the most common type of specific tumor in cats. The study of cancer, known as oncology, is a growing field in veterinary medicine.

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