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Animal Diseases Modified by Georgia Agricultural Education Office June, 2002 August 2008 Disease • Broad definition – not being at ease or uncomfortable • Producers have a vested interest to keep their animals healthy August 2008 Healthy Animals • Grow faster and produce more profit for their owners • Some diseases are mild, others may be severe and cause rapid death August 2008 Sick animals • Usually display outward signs of illness • Animal may be droopy, go off feed and water, be restless, have a dull haircoat August 2008 Infectious diseases • Caused by microorganisms that invade the animal’s body • Usually contagious diseases that the animal can pass to another animal August 2008 Bacteria • Live in a wide range of conditions • Live on and in the bodies of all animals • More numerous than the cells of the body August 2008 Bacteria • Many are beneficial • Those living in the stomachs of ruminant animals aid in digestion August 2008 Bacteria • Useful in production of foods such as cheese and sauerkraut • Many can be harmful • Invade the cells of an animal’s body August 2008 Parasitic bacteria • May harm the animal by feeding off the body cells or secreting a material known as a toxin August 2008 Toxin • Substance that causes harm to an organism • A poison August 2008 Harmful bacteria • When large numbers invade, the animal becomes ill • Type and form of the illness depends on the type of bacteria that invades the animal August 2008 Cocci • Round spherical shaped bacteria • Some forms of pneumonia and strep are caused by this bacteria August 2008 Bacillus • Rod shaped • Single, pairs, or arranged in chains • Cause some serious diseases in animals August 2008 Bacillus • Anthrax • Tetanus • Blackleg • Intestinal coliform • Salmonella and tuberculosis August 2008 Spirilla • Shaped like spirals or corkscrews • Very motile • Require moist atmosphere to live August 2008 Spirilla • Live very well in the reproductive tracts of animals • Leptospirosis • Vibrosis and spirochetosis August 2008 Most bacteria • Can be controlled by the use of antibiotics • Penicillin was one of the first • Produced from extracts of molds August 2008 Penicillin • Many forms are now produced • Very effective against bacterial infection. August 2008 Viruses • Very tiny particle of matter composed of a core of nucleic acid and a covering of protein that protects the virus August 2008 Viruses • Have characteristics of both living and nonliving material • Are on the borderline between living and non living August 2008 Viruses • Made up of some of the material found in cells but are not cells because they do not have a nucleus or other cell parts. August 2008 Viruses • Do not grow and cannot reproduce outside a living cell • Once inside a living cell, virus reproduces using energy and materials in the invaded cell August 2008 Viruses • Harm cells by causing them to burst during reproduction • And by using material that the cell needs to function properly August 2008 Virus • Viral diseases cause the animal to be sick by preventing certain cells in the body from functioning properly August 2008 Virus • More difficult to treat than bacterial diseases • Antibiotics are not effective against viral infections August 2008 Viral diseases • Foot and mouth disease • Influenza • Hog cholera • Pseudorabies August 2008 Viral diseases • Best means of dealing with them is prevention August 2008 Protozoa • Microorganism that causes disease • Single celled organisms that are often parasitic August 2008 Protozoa • Cause harm by feeding on cells or producing toxins • African sleeping sickness • Anaplasmosis August 2008 Protozoa • Coccidiosis • One of the most costly poultry diseases • Caused diarrhea and weight loss August 2008 Protozoa • Most can be controlled by drugs August 2008 The immune system • Several lines of defense in fighting disease • Physical barriers that keep pathogens out August 2008 The immune system • Nostrils are lined with hairs that attract particles that harbor germs before they can enter the body August 2008 The immune system • Mucous membranes secrete viscous water substance that traps and destroys bacteria and viruses August 2008 The immune system • Digestive and respiratory systems – greatest avenue for entry • Some disease germs can live in the soil for many years August 2008 Soil borne disease • Animals come into contact with the ground when they graze • Many pathogens are breathed in by livestock August 2008 Germs • Swallowed by animals are destroyed by digestive enzymes • Inhaled germs are trapped in mucous membranes of respiratory tract August 2008 nd 2 line of defense • Blood cells • White and Red • Red – carry oxygen and other nutrients to other body cells August 2008 White Blood Cells • Are produced in the bone marrow • Circulate throughout the body to get rid of worn out cells August 2008 Phagocytes • White blood cells that intercept and destroy pathogens • Also migrate to certain organs and remain there to intercept pathogens August 2008 White Blood Cells • Circulate through other body fluids and the mucous membranes August 2008 Phagocytes • Release chemicals that can induce the production of more white blood cells to help fight disease August 2008 Phagocytes • An elevated WBC count indicated that there are disease organisms present in the animal’s body and a large number of phagocytes have been produced to combat them August 2008 Lymphocytes • Lymph glands that produce certain WBC’s • These cells react to foreign substances by releasing chemicals that kill the pathogen or inactivate the foreign substance August 2008 Antigens • Substances that cause the release of chemicals • May be viruses, bacteria, toxins, or other substances August 2008 Antibodies • The chemicals released by the lymphocytes August 2008 nd 2 Immune Response • Lymphocytes become memory cell and are ready to release the antibody if the antigen enters the body at a later time August 2008 nd 2 Immune Response • Response occurs much more quickly • Lasts longer than primary response August 2008 Immunity • Means than an animal is protected from catching a certain disease • Animal’s body is capable of producing enough antibodies fast enough to neutralize the disease August 2008 Immunity • Active or passive • Active –animal is more or less permanently immune • Passive – animal is only temporarily immune August 2008 Immunity • Animals are born with some immunity • Colostrum is rich in antibodies • Serve the new animal until its own immune system can take over August 2008 Immunity • As the animal is exposed to more antigens, antibodies build up within the animal. • Naturally acquired active immunity results from the animal actually contracting the disease and recovering August 2008 Artificial Active • Induced by injecting antigens into the animal • Causes phagocytes to react without making the animal seriously ill August 2008 Edward Jenner • Late 1700’s • Began vaccination process • Smallpox and cow pox • Collected material from sores of people with cowpox August 2008 Edward Jenner • Injected healthy people with material • Became mildly ill with cow pox • Then were immune August 2008 Louis Pasteur • Developed several vaccines following Jenner’s lead August 2008 Vaccines • Live • Killed or weakened strain • Both stimulate production of antibodies • Killed – less dangerous when compared to live vaccine August 2008 Noninfectious Disease • Not contagious • Genetic diseases • Caused by defects in the genes • Problem or disease can be passed from parent to offspring August 2008 Genetic Diseases • Cannot be spread through contact with other animals • Control of genetic diseases, using good selection practices • Avoid breeding animals that are known to have genetic defects in their line August 2008 Nutritional Diseases • Milk fever in dairy cattle • Cows lie down and are unable to stand • Insufficient amount of Ca in the bloodstream August 2008 Milk fever • Usually cured by injection of Ca salts • Effects are immediate and dramatic August 2008 Overeating • Founder – horses, cattle and sheep • Eat too much grain • Causes feet to become inflamed and hooves to grow upward and outward August 2008 Poisoning • Moldy feed can contain toxins • Aflatoxins and ergot – fungi that grow on grains • Grazing on poisonous plants August 2008 Disease prevention • Vaccination • Humans can carry disease from one farm to another • Many farms require plastic boots be worn over the shoes of visitors August 2008 Quarantine • Isolation of newly purchased animals • Government regulates quarantine for animals coming into the US August 2008 Quarantine • Many states have quarantine periods or require health papers for animals crossing state lines • Animals tested positive for Brucellosis (Bangs) are branded and sent to slaughter. August 2008