Caused by bacteria and viruses Diseases Caused by bacteria and viruses

Disease causing agents PATHOGENS Disease causing agents Viruses reproduce by infecting living cells and can cause harm to the host Bacteria requires nutrients and energy which can interfere with the host’s ability to function properly

Bacterial disease in humans The growth of bacterial pathogens disrupts the body’s normal functions Louis Pasteur (French chemist) was the first person to show that bacteria causes diseases Established the Germ Theory

Bacteria produces disease in 2 ways directly breaking down cells for food Ex. Mycobacterium tuberculosis (Tuberculosis) is inhaled into the lungs where it destroys lung tissues. It can also enter a blood vessel and travel to new sites releasing toxins (poison) that travel through the host Ex. Streptococcus (strep throat) releases toxins into the bloodstream, causing scarlet fever Ex. Corynebacterium diphtheriae (Diphtheria) releases toxins in the throat and causes breathing problems, heart failure, paralysis, and death.

Preventing Bacterial disease Vaccine Many bacteria diseases can be stopped by stimulating the body’s immune system Antibiotics- compounds that block the growth and reproduction of bacteria Ex. Penicillin and tetracycline

Bacterial disease in animals Animals can be infected by bacterial disease as well Which can transmit to ranchers and animal handlers Ex. Bacillus anthracis (anthrax) are often found in sheep Produces tough, resistant spores that can last for years Was developed as a biological weapon Sverdlovski (Soviet Union) in 1979 hundreds of people died when anthrax was accidently released.

Controlling bacteria Although most bacteria are harmless (many are beneficial), there are various methods used to control the growth of bacteria. Sterilization Destroys all bacteria through the use of heat as most bacteria can’t survive high temperature for a long time

Controlling bacteria Disinfectants Chemical solutions that kill pathogenic bacteria (AKA antibacterial products) Overuse of antibacterial products increases the chances that common bacteria will evolve to become more resistant and therefore more dangerous and difficult to kill

Food storage and processing Controlling bacteria Food storage and processing Refrigeration stores food at lower temperatures which keeps it fresher Raising the temperature of the food to the point where bacteria are killed Ex. Boiling, frying, or steaming

Viral diseases in humans Viruses attack and destroy certain cells causing symptoms of the disease Ex. Polio virus infects and kills cells of the nervous system producing paralysis Some viruses will infect cells to change their patterns of growth and development Vaccines are a way to prevent viral diseases Many decades of childhood vaccines against smallpox have virtually eliminated this disease

Viral disease in animals Ex. An epidemic of foot-and-mouth disease infected thousands of cattle in Europe in the late 1990’s Some animal viruses can cause cancer Oncogenic – tumor-causing viruses

Viral disease in plants Viruses can also infect plants Ex. Tobacco mosaic virus, potato virus, etc Many plant viruses are spread by insects

Viral disease in plants Plant viruses contain a core of nucleic acid and a protein coat, however, they have a hard time entering plant cells due to the cell walls Plant viruses developed a way to take advantage of even minor damage to plant tissues (ex. Tears in leaves, breaks in stems and roots, or microscopic cell wall damaged caused by human or animal contact)