1. THE NATURE OF DISEASE

2. Immune System The immune system of the human body is made up of: Cells
Molecules
Organs
that act together to defend the body against foreign invaders that may cause disease.
The health of the body is dependent on the immune system’s ability to recognize and then repel or destroy these invaders
It is designed to defend you against millions of bacteria, microbes, viruses, toxins and parasites that can invade your body.

3. PATHOGENS Pathogens: disease causing agents
Ex. Bacteria, Viruses, Parasites
Pathogens are found in soil, contaminated water, and infected animals, including other people

4. Birth Before you are born your body is free of pathogens.
At birth microorganisms establish themselves on
your skin
respiratory system
urinary system
reproductive system
intestinal tract

5. INFECTIOUS DISEASES
Infectious Diseases: any disease caused by the presence of a pathogen in the body
These microorganisms have a symbiotic relationship with your body…
However, if you become injured or weak these same organisms can become pathogens.

6. EX. ZOONOSIS: An infectious disease transmissible under natural conditions between animals and human.

7. Examples of Infectious Diseases
Cause
Affected Organ System
Transmission
Smallpox
Virus
Skin
Droplet
Colds
Respiratory
Direct contact
Influenza
Food
Poisoning
Bacteria
Digestive
Contaminated food
Rabies
Nervous
Animal bite

9. What causes a disease? Not all disease are caused by pathogens
Example: Hemophilia- recessive allele on the X chromosome
Pathogens can also cause some cancer

10. Robert Koch Robert Koch 1876 discovered that pathogens caused disease
Studying Anthrax
Would inject it into animals, they would get sick then he would isolate the bacteria in their blood and compare them to the anthrax he isolated from other victims.

11. Reservoirs of Pathogens
Living Reservoirs
People often carrier a pathogen and pass it to others without knowing it
Animals can also pass on the flu or rabies to humans
Nonliving Reservoirs
Soil contains pathogens such as fungi and bacteria that can cause food borne illnesses
Water contaminated with human waste contains bacteria that cause intestinal illnesses

12. Transmission Pathogens are transmitted to humans by:
Direct Contact (Examples to Follow)
Through an Object
Doorknob, Tabletop, Faucet handle
Through the Air
Coughing and Sneezing
Through an Intermediate Organism
Fleas, Ticks, Mosquitoes, Rats

13. Transmission Direct contact Person to person.
An easy way to catch most infectious diseases is by coming in contact with someone who has one. This "someone" can be a person, an animal or, for an unborn baby, its mother.
Person to person.
Most common- direct transfer of bacteria, viruses or other germs from one person to another. (touches, coughs on or kisses someone who isn't infected).

14. Transmission Animal to person. Mother to unborn child.
Being bitten or scratched by an infected animal can make you sick and, in extreme circumstances, could even cause death. Handling animal waste can be hazardous, too. For example, you can acquire a toxoplasmosis infection by scooping your cat's litter box, particularly if you're pregnant.
Mother to unborn child.
A pregnant woman may pass germs that cause infectious diseases to her unborn baby. Germs can pass through the placenta.

15. Transmission Indirect contact Disease-causing organisms can
also be passed along by indirect contact.
Many germs can linger on an inanimate object, such as a tabletop, doorknob or faucet handle.
You can pick up the germs he or she left behind. If you then touch your eyes, mouth or nose before washing your hands, you may become infected.
Some infections occur from organisms that naturally live in the environment but are not passed from person to person. Example anthrax.

16. What Causes a Symptom
Pathogens can over come the defense of your immune system, they can multiply causing damage to the tissues.
Viruses can cause death to the cells in which they invade
Toxins are poisons which can be produced by microorganisms
The poisons can be transmitted to the blood
Some toxins produce fever, destroy blood cells, and proteins synthesis

17. PATTERNS OF DISEASE Center for Disease Control and Prevention (CDC):
Government Health Department that identify pathogens, their method of transmission, and geographic distribution
Endemic Disease: disease that is continuously present in the population
Ex. Common cold

18. Patterns of Disease
Epidemic- widespread outbreak of an infectious disease; many people are infected at the same time
Pandemic- epidemic over a wide geographical area; "a pandemic outbreak of malaria.”

19. Treating Disease
Antibiotics- produced by microorganisms that in small amounts will kill or inhibit the growth and reproduction of other microorganisms
Can be used to cure bacterial infections but does NOT affect viruses.

20. Antibiotic Resistance
Think back…
What is antibiotic resistance again?

21. The Body’s Fight Against Disease
Immune Response
The Body’s Fight Against Disease

22. The Skin 1st line of defense Acts as a physical barrier
How do pathogens enter the skin?

23. Body Secretions
Mucus: traps things entering digestive and respiratory tracts
Sweat, Tears, Saliva: contain enzyme lysozyme that help digest cell wall of some bacteria cells

24. Inflammation Occurs at the site of an infection
Fluid leaks into injured tissue helping to isolate and destroy pathogens
Symptoms include redness, swelling, pain, and heat
Inflammation begins when damaged tissue cells and white blood cells called basophils release histamine.

25. So what is an antihistamine?
Causes blood vessels in the injured area to dilate-makes them more permeable to fluid.
Dilated BV cause the redness of the inflamed area.
Fluid leaks out from the vessels to help destroy toxic agents.
So what is an antihistamine?

26. Fever Fever refers to an elevation in body temperature.
Normal oral measurement of 98.6 F (37 C)
Body temperature can also vary up to 1 F (0.6 C) throughout the day.
Fever is not considered medically significant until body temperature is above F (38 C).
Fever serves as one of the body's natural defenses against bacteria and viruses which cannot live at a higher temperature.
For that reason, low fevers should normally go untreated, unless accompanied by troubling symptoms.

27. White Blood Cells (WBC)
White Blood Cells- defend against pathogens

28. Phagocytes
White Blood Cells that destroy pathogens by surrounding them and engulfing them
Phagocytes include macrophages, neutrophils, monocytes and eosinophils
Macrophages-found in body tissues
Others are found in the blood

29. Phagocytosis

30. The Lines of Defense
Macrophages- WBC that provide the 1st line of defense when pathogens enter the tissues
If they get past the macrophages the next line is neutrophils
3rd line- Monocytes -immature macrophages which circulate in the blood

31. Lines of Defense Cont.
Monocytes can squeeze through blood vessels to the infected area
Once they reach the infected area they become as large as mature macrophages and engulf the dead neutrophils and pathogens
When the infection is over, some monocytes mature into tissue macrophages that remain in that area to fend of new infections

32. PUS Fluid that forms at site of infection
Made of dead macrophages and body fluid
Formation continues until the infection is over
Cleared away by macrophages

33. Questions What is the immune system? What does WBC stand for?
What is the function of a WBC?
What are some ways that your body fights infections?
How can infections be transmitted?

34. Parasites
An animal or plant that lives in or on a host (another animal or plant); it obtains nourishment from the host without benefiting or killing the host

35. Where can parasites be found?
Can be found in:
Meat
Unsanitary areas
Insects (like mosquitoes)
Fish
Snails
Dogs
Cats
HUMANS

36. 28 foot tapeworm
roundworms

37. **Interesting Facts**
The longest tapeworm ever removed from a human came out on September 05, 1991.
In all, doctors pulled a 37 foot tapeworm out of a body through the mouth.
Whale tapeworms can grow up to 120 feet long.

39. Questions What is a parasite? Where can they be found?
What makes them a parasite?