pathogens

• Diseases: Communicable – Can be transmitted from one person to the other.

  Non-Communicable – Cannot be transmitted from one person to the other.
• Pathogens are micro-organisms that cause diseases.
• The four types of pathogens are bacteria, viruses, fungi and protists.
• Features of Bacteria:

  •They are prokaryotes - single celled organisms.

  •They do not have a true nucleus, but a circular strand of DNA.

  •They do not contain mitochondria.

  •They may have a tail, known as a flagellum, to help it move.

  •They produce toxins that damage cells and tissues.

  •They are living cells.

  •The largest bacteria are 10 micrometres long.

  •Examples: lactobacillus, salmonella, staphylococcus, E.coli
• Features of Viruses:

  •They are not cells.

  •They are much smaller than bacteria.

  •They reproduce rapidly inside host cells.

  •They consist of genetic material and a protein coat.

  •Measles, mumps, chicken pox and colds are all caused by viruses.
• •Once inside a cell, viruses can make thousands of copies of itself. •This continues until the cell bursts open.

  •It is this cell damage that makes humans feel unwell.
• Features of Protists:

  •Protists, or protozoa, are eukaryotes.

  •They are single celled organisms.

  •They can be parasitic, this means they live on or inside another organism causing harm.

  •They can be animal-like, plant-like, or fungi-like.

  •Malaria is a well-known illness caused by protists and transmitted by mosquitos.
• Life Cycle of Malarial Protists:

  •A healthy person is bitten by an infected mosquito.

  •The parasite is injected into the blood stream.

  •The parasite invades the liver and red blood cells causing the illness to develop.

  •If a mosquito feeds on the blood of an infected person, the parasite enters the mosquito.

  •When the mosquito feeds on a healthy person, the parasite is passed on.
• Features of Fungi:

  •Toadstools, mushrooms and moulds are examples of multi-cellular fungi.

  •The cell wall of fungi is made from chitin.

  •Fungi use saprotrophic nutrition - they secrete enzymes to digest food and then absorb it.

  •Fungi have thread like structures called hyphae.

  •Hyphae can produce spores enabling the fungus to be easily spread.
• Pathogens are spread through the air, water, and direct contact with an infected person, however sometimes it can spread through indirect contact.
• The spreading of pathogens and disease is known as transmission.
• Transmission by air


  • A cough or a sneeze can release millions of microorganisms into the air which could then infect somebody else
• Transmission by water


  • Dirty water can transmit many diseases, for example, cholera which can be transmitted by drinking the water
• Transmission by animals


  • An animal, eg. a mosquito which can spread the protist malaria, can carry the pathogen from one place to another
• Transmission by contact

  • Direct contact: by the contact of hands, sexual contact, skin to skin contact
  • Indirect contact: when an infected person sneezes or coughs which sends infectious droplets into the air, if mother has HIV/AIDS it can be passed on to the unborn child through the placenta
• • Vectors are organisms which passes pathogens from one organism to another, eg. mosquitoes
• Infectious disease-illness that can be caught from a pathogen
• • Common disease symptoms are a high temperature, headaches and rashes, which are caused by the damage and toxins produced by the pathogens.
  • The symptoms also appear as a way your body responds to the damage and toxins from the pathogens.
  • You catch an infectious disease when you pick up a pathogen from someone else who is infected with the disease.