Bio C7 - Pathogens

What is a disease?

-A pathological condition of body parts or tissues characterised by an identifiable group of signs and symptoms

Parasites - amoebae & flagellates

-Neither a bacteria or a virus (has a nucleus)

What is a vector?

-An organism that doesn’t contain the disease itself, but spreads the infection

What is an infectious disease?

-Disease caused by an infectious agent such as a bacterium, virus, protozoan, or fungus that can be passed on to others

What are the 4 types of infectious diseases?

-Bacteria

-Viruses

-Fungi

-Parasites

What is an infection?

-Occurs when an infectious agent enters the body and begins to reproduce; may or may not lead to disease

What is a pathogen?

-An infectious agent that causes disease

What is a host?

-An organism infected by another organism

What is virulence?

-The relative ability of an agent to cause rapid and severe disease in a host

What are Koch’s 4 postulates?

1.The specific agent must be associated with every case of the disease

2.The agent must be isolated from a diseased host and grown in culture

3.When the culture-grown agent is introduced into a healthy susceptible host, the agent must cause the same disease

4.The same agent must again be isolated from the infected experimental host

What are the different groups of agents that cause disease?

–Bacteria

–Viruses

–Protozoa (Protists)

–Fungi

–Helminths (Animals)

For a microorganism to be considered a pathogen it must:

• Gain entry to the host

• Colonise the tissues of the host

• Resist the defences of the host

• Cause damage to the host tissues

What is transmission?

-The transfer of a pathogen from one individual to another

How do microorganisms gain entry to the host?

•Penetration of one of the organism’s interfaces with the environment —> the skin

•This forms a thick, continuous layer, which is an effective barrier to infection

•Invasion usually occurs when the skin is broken by cuts/abrasions/bites

•Some interfaces of the body have evolved to allow exchange of material between the internal and external environments

How do pathogens cause disease?

-Pathogens affect the body in two main ways —> by damaging tissues & producing a toxin

-Damages tissue by preventing tissues from functioning due to the number of pathogens causing damage

-Viruses prevent the synthesis of DNA, RNA and proteins by the host cell

-Pathogens produce toxin

Examples of infectious diseases:

-TB —> airborne

-Athletes’ foot —> fungi

-Chicken pox —> virus

-Tenatus —> bacterial infection

-AIDS —> caused by HIV virus

-Food poisoning —> caused by bacteria

What is epidemiology?

-The study of the incidence (number of cases) and pattern of a diease, and is used to find the means of preventing