Pathogens

PathogensMr. Mah

Living EnvironmentLecture 11

Warm-Up

• Take 3 minutes to write down as many diseases/illnesses you can think of!

• Now, put a dot beside the ones you think can be spread or caught. Underline the ones you do not think can be spread or caught.

•SWBAT identify various types of pathogens and

their effect on an organism’s homeostasis.

What is a Disease?

• A disease is any medical condition or physical abnormality that does not allow the body to function normally and throws off homeostasis

Communicable vs. Non-Communicable

• Diseases can be grouped into two major categories: the kind that can be spread from one person or object to another person or object and the kind that cannot be spread

• Communicable Disease - Any disease that is infectious (can be spread)

• Non-Communicable Disease - Any disease that is not infectious and is instead either genetic or caused by lifestyle factors (i.e smoking)

Human Infectious Disease

Disease Cause Affected Organ System TransmissionSmallpoxChicken poxRabiesPoliomyelitisColdsInfluenzaHIV/AIDSHepatitis BTetanusFood poisoningStrep throatDiptheriaTuberculosisSpinal meningitis

VirusVirusVirusVirusVirusVirusesVirusesVirusVirusBacteriaBacteriaBacteriaBacteriaBacteriaBacteria

SkinSkinNervous systemNervous systemRespiratory systemRespiratory systemImmune systemLiverNervous systemDigestive systemRespiratory systemRespiratory systemRespiratory systemNervous system

DropletDropletAnimal biteContaminated waterDirect contactDirect contactExchange of body fluids

Exchange of body fluids

Puncture woundContaminated food/water

DropletDropletDropletDroplet

Communicable Diseases

• The reason communicable diseases are infectious is because they are caused by pathogens that can travel from one person or object to another

• Communicable diseases can be spread through:- viruses- parasites- bacteria- fungi

Examples of Communicable Diseases

• Common cold• Flu• All STDs (AIDS, syphilis, herpes)• Mono• Chicken pox• Malaria• Ringworm • Food poisoning

• For a disease to continue and spread, there must be a continual source of the disease organisms.

The Spread of Infectious Diseases

• This source can be either a living organism or an inanimate object on which the pathogen can survive.

• The body can be a reservoir of disease-causing organisms.

Reservoirs of pathogens

• People may transmit pathogens directly or indirectly to other people.

• Sometimes, people can harbor pathogens without exhibiting any signs of the illness and unknowingly transmit the pathogens to others.

Reservoirs of pathogens

• These people are called carriers and are a significant reservoir of infectious diseases.

• Pathogens can be transmitted to a host from reservoirs in four main ways:

• 1. Direct contact• 2. By an object, • 3. Through the air,• 4. By an intermediate

organism called a vector.

Transmission of disease

• The common cold, influenza, and STDs are spread by direct contact.

• Bacteria and other microorganisms can be present on nonliving objects such as money, toys, or towels.

Transmission of disease

• Transmission occurs when people unknowingly handle contaminated objects.

Transmission of disease• Airborne transmission of a disease can occur

when a person coughs or sneezes, spreading pathogens contained in droplets of mucus into the air.

• Diseases transmitted by vectors are most commonly spread by insects.

Transmission of disease

• Diseases such as malaria and the West Nile virus are transmitted by mosquitoes.

Transmission of disease• Lyme disease and Rocky Mountain spotted

fever are diseases that are transmitted by ticks.

• Flies also are significant vectors of disease.

Transmission of disease

• They transmit pathogens when they land on infected materials, such as animal wastes, and then land on fresh food that is eaten by humans.

• When a pathogen invades your body, it encounters your immune system.

What causes the symptoms of a disease?

• If the pathogen overcomes the defenses of your immune system, it can metabolize and multiply, causing damage to the tissues it has invaded, and even killing host cells.

• Most of the damage done to host cells by bacteria is inflicted by toxins.

Damage to the host by viruses and bacteria

• Toxins are poisonous substances that are sometimes produced by microorganisms.

• These poisons are transported by the blood and can inhibit protein synthesis in the host cell, destroy blood cells and blood vessels, produce fever, or cause spasms by disrupting the nervous system.

Damage to the host by viruses and bacteria

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

Treating Diseases

• Although antibiotics can be used to cure some bacterial infections, antibiotics do not have an effect on viruses.

• With the continued use of antibiotics, bacteria can become resistant to the drugs.

Treating Diseases

• That means the drugs become ineffective.

• Penicillin, an antibiotic produced by a fungus, was used for the first time in the 1940s and is still one of the most effective antibiotics known.

• The use of antibiotics is only one way to fight infections.

Treating Diseases

• Your body also has its own built-in defense system—the immune system—that works to keep you healthy.

Non-Communicable Diseases

• Non-communicable diseases are NOT caused by pathogens

• Non-communicable diseases can be genetic (meaning that you carry a gene that makes your body not function the way it is supposed to)

• Non-communicable diseases can also be caused by bad habits and external factors (for example, smoking can cause you to develop lung cancer)

Examples of Non-Communicable Diseases

• Sickle cell anemia• Diabetes• Cancer• Asthma• Heart problems• Allergies