Post on 11-Jan-2016
transcript
Chapter 19-3: Diseases Caused by Bacteria and Viruses
• Bacteria and viruses are everywhere in nature, but only a few cause disease.
• Disease-causing agents are called pathogens.
Bacterial Disease in Humans• Many bacteria live
on and within our bodies.
• Growth of pathogenic bacteria disrupts the body’s equilibrium by interfering with its normal activities and producing disease.
How do bacteria cause disease?
1. They damage the cells and tissues of the infected organism directly by breaking down the cells for food.
2. Or they release toxins (poisons) that travel throughout the body interfering with the normal activity of the host.
Preventing Bacterial Disease
• Many bacterial diseases can be prevented by vaccines (a preparation of weakened or killed pathogens).
• When injected into the body, a vaccine may prompt the body’s immunity to the disease.
Treating Bacterial Disease• If infection occurs, drugs can
be used to destroy bacteria. • These drugs include
antibiotics, which are compounds that block the growth and reproduction of bacteria.
• A reason for increased human life expectancy is an increased understanding of how to prevent and cure bacterial infections.
Viral Disease in Humans• Viruses produce disease by disrupting the
body's normal equilibrium.• How do viruses cause disease?
1. Lytic: viruses can attack and destroy certain cells in the body, causing symptoms of the disease.
2. Lysogenic: other viruses cause infected cells to change patterns of growth and development.
Viral Disease Prevention/Treatment
• Vaccines are the best protection against viral diseases, but only work if used before an infection begins.
• Viral diseases cannot be treated with antibiotics.
• Symptoms may be treated with over-the-counter medicines.
Bacterial Diseases Viral Diseases
• Lyme disease
• Tetanus
• Tuberculosis
• Bacterial meningitis
• Strep throat
• Common cold
• Influenza
• AIDS
• Chicken pox
• Hepatitis B
• West Nile
40-1: Infectious Disease
• Disease: any change, other than an injury, that disrupts the normal function of the bodyo Can be inherited, caused
by materials in the environment, or produced by pathogens (disease causing agents).
The Germ Theory of Disease• Idea that infectious
diseases are caused by microorganisms, or germs
• Observed by French chemist Louis Pasteur and German bacteriologist Robert Koch
Koch’s Postulates• Series of guidelines used
to identify the microorganism that causes a specific disease
• These rules are important because identifying pathogens that cause disease is the first step toward prevention or cures.
The Postulates (or rules)1. The pathogen should always be found in a
sick organism, not a healthy one.2. It must be isolated and grown in the lab.3. When injected in a new host, it should cause
the same original disease.4. The injected pathogen should be isolated
from the new host and identical to the original pathogen.
Agents of Disease• For many pathogens, the human body
provides just the right conditions for growth.
Agent Example
Viruses Common cold, flu, warts
Bacteria Botulism, Anthrax
Protists Malaria, African Sleeping Sickness
Worms Schistosoma
Fungi Athletes foot, ringworm
Fungi: athlete's foot
Worms:
SchistosomaProtists:
Trypanosoma
How Diseases Are Spread
• Coughing, sneezing, or physical contact
• Contaminated food or water
• Vectors: infected animals that carry pathogens from person to person
Fighting Infectious Diseases• Antibiotics: compound that blocks the growth
and reproduction of bacteria (no effect on viruses)
• Over-the-Counter Drugs: treat only the symptoms, but do not actually treat the cause of the infection