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DISEASES CAUSED BY BACTERIA AND VIRUSES
Chapter 19 Pgs 485-490
BACTERIAL DISEASE IN HUMANS
Bacteria produce disease in one of two general ways. Some bacteria damage the cells and tissues of the infected organism directly by breaking down the cells for food. Tuberculosis—is inhaled through the lungs, where
it destroys the lung tissue. Other bacteria release toxins (poisons) that
travel throughout the body interfering with the normal activity of the host. Streptococcus (strep throat)—releases toxins into
the bloodstream: can also cause scarlet fever.
PREVENTING BACTERIAL DISEASE
Many bacterial diseases can be prevented by stimulating the body’s immune system with vaccines. Vaccine—preparation of weakened or killed
pathogens Prompts the body to produce immunity to the disease
If a bacterial infection does occur, a number of drugs can be used to attack and destroy the invading bacteria. Antibiotics—compounds that block the growth and
reproduction of bacteria.
CONTROLLING BACTERIA
Various methods1. Sterilization by Heat—most bacteria cannot
survive high temperatures for a long period of time, so most can be killed by exposure to high heat.
2. Disinfectants—chemical solutions that kill pathogenic bacteria. Overuse increases the likelihood that common bacteria will evolve to become resistant to them.
3. Food Storage—Food stored at low temperatures will stay fresh longer because the bacteria will take longer to multiply.
VIRAL DISEASE IN HUMANS
Like bacteria, viruses produce disease by disrupting the body’s normal equilibrium.
In many viral infections, viruses attack and destroy certain cells in the body, causing the symptoms of the disease.
Cannot be treated with antibiotics.
Best protection lies in prevention.
VIRAL DISEASE IN ANIMALS
Viruses produce serious animal diseases as well.
Foot-and-mouth disease that swept through Europe in the late 1990—thousands of cattle were destroyed.
Some animal viruses can cause cancer.
VIRAL DISEASE IN PLANTS
Many viruses infect plants. Serious threat to many
agricultural crops. Many plant viruses are
spread by insects. Feeding action of an insect
pest often provides a perfect opportunity for viral infections to spread.
VIROIDS AND PRIONS
Viruslike particles that can also cause disease
1. Viroids—cause disease in plants1. Single-stranded RNA molecules that have no surrounding
capsids2. Viroids enter an infected cell and direct the synthesis of new
viroids3. Then disrupt the metabolism of the plant cell
and stunt the growth of the entire plant
2. Prions—cause disease in animals1. Cause disease by forming protein clumps2. Contain no DNA or RNA3. Strong evidence that mad cow disease is caused by prions
PICTURE CREDITS
http://www.virology.net/big_virology/EM/polio1.gif
http://ledaomd.files.wordpress.com/2008/10/hand-foot-mouth.jpg
http://www.ourmed.org/images/1/11/Hand_foot_mouth_disease.jpg
http://images.dailytech.com/nimage/10351_plant_virus.jpg
http://www.mcb.uct.ac.za/tutorial/Image62.gif
http://www.peta.org/cfs-filesystemfile.ashx/__key/CommunityServer-Components-SiteFiles/Peta-Images-Main-Sections-Living/200_2D00_LivingVegMadCow.jpg
http://www.ars.usda.gov/sp2UserFiles/person/2273/viroids1a.jpg