Nature of Disease

Defense against pathogens• Pathogen = an organism that

causes a disease. Ex: Bacteria, virus, fungus, protozoa, etc.

• Where do we get pathogens?– Contaminated water/food– Soil– Infected animals/people– Vectors (ex. Fly's)

• Any disease caused by a pathogen is called an infectious disease.

Streptococcus pneumoniae

Giardia

Types of Disease and their Causes

Disease Cause System

Hemophilia GeneticRecessive Allele X

CirculatoryBlood-Clotting

Sickle Cell Anemia Genetic Circulatory Anemia

Cirrhosis Exposure to Toxins or chemicals-Alcohol

Liver

Scurvy MalnutritionDeficiency Vitamin C

Poor wound healing, swollen gums, teeth loosening teeth

Osteoarthritis Wear and tear of joints. Skeletal Joints

Koch’s PostulateCause: Looking for cause of Anthrax Disease

–Affects mainly sheep and cows

Step 1)Discovered rod-shaped bacterium in dead animal red blood cells.

Step 2)Cultured the bacteria on nutrientsStep 3)Injected the cultured bacteria into

healthy animals.• Healthy animal dies

Step 4)Koch finds the same rod-shaped found in newly infected animal’s blood.

Spread of Infectious Disease

• Reservoirs (Source) of infectious disease can be living or non-living.

• The main living source of disease is the human body.

Types of Reservoirs

• Reservoirs of infectious disease:– Living Reservoirs : the human body, animals, plant – Non-living Reservoirs: Soil and water

Rabid dog is a living reservoir for the rabies infection

Sewage Spills In San Diego’s San Marcos Creek

November 8,2010 the Department of Environmental Health said an estimated 5,440 gallons of waste flowed into the creek that empties into La Costa's Batiquitous Lagoon in Carlsbad and the ocean

Submitted by Marina Dimova on 2010, November 8 - 12:38

Non-Living Reservoir Water

Four Main Types of Disease Transmission

• Direct contact: Cold, Influenza, STD’s– Direct body contact, exchange of body fluids

• By an Object: Bacteria– Eating Utensils, Cups, Toys

• Through the air: Streptococcus; Strep Throat– Through water droplets in cough and sneeze

• By and intermediate organism– Vector: Fly, Mosquito, Rats perseverance

Sneeze Video

http://www.youtube.com/watch?v=LzH-yat-mBI

Symptoms of Disease• Steps of infection:

– Pathogen enters body

– Immune system responds to invasion • May cause redness, swelling, fever, pus,

inflammation

– If pathogen overcomes the body’s defense pathogen metabolizes and multiplies.

– May cause damage to tissues that it has invaded, host cells may die.

Damage to Host Cell Virus

-Host cell taken over by virus-Virus takes over genetic and metabolic function

of cell-Host cell is damaged and may die

Bacteria -Bacteria creates toxins that can be transported by blood to different areas in the

body.-Serious and sometimes fatal effects occur

Types of Damage

• Bacterial toxins can-– inhibit protein synthesis in host cells, – destroy blood cells and blood vessels,– produce fever – cause spasm from damage to the nervous system.

Types of Bacterial ToxinsTetanus bacteria-

-Affects nerve cells and causes uncontrolled muscle spasm.-If left untreated may cause paralysis and death-Tetanus bacteria is found in soil

Streptococcus bacteria- -Causes Strep Throat-Causes fever and severe sore throat

Botulism bacteria- -Enters through the digestive tract or through a skin

wound -Causes paralysis of the face and if left untreated may

cause respiratory paralysis

Patterns of Disease

Endemic- A disease that is constantly present in a population.Example: Common Cold

Epidemic-Many people in a given area are afflicted with the same disease at about the same time.Examples: Polio and Small Pox

Polio – Epidemic in United States in the early 1950’s. Victims are left paralyzed or died. Those that survived often were required to go on the breathing machine the iron-lung.

Polio

• Polio – Epidemic in United States in the early 1950’s. Victims are left paralyzed or died. Those that survived often were required to go on the breathing machine the iron-lung.

Antibiotic

• An antibiotic is an substance produced by a microorganism that, in small amounts, will kill or inhibit the growth and reproduction of the of the microorganism.

• Antibiotics a produced naturally by various species of bacteria and fungus.

• Antibiotics do not affect viruses because they do not have a live and reproduce in a host cell.

Resistant Bacteria

• With continued use antibiotics certain bacteria can become resistant to certain antibiotics.

• The bacteria evolve to become resistant to the bacteria.

• Resistant bacteria can create enzymes to break down the antibiotic.

• Streptococcus pneumonia is one type of penicillin resistant bacteria.