Types of Pathogen
- Communicable diseases are spread by pathogens
- A pathogen is any microorganism that causes disease in another organism (e.g. in plants or animals)
- Many microorganisms are pathogens including:
- Bacteria
- Fungi
- Protists (protoctists)
- Viruses
- Not all species within these groups (apart from the viruses) are pathogens, as many bacteria, fungi and protists are harmless and do not cause disease
- However, all viruses are pathogenic as they can only exist by living inside the living cells of other organisms (or by using these cells to create more viruses)
Pathogenic bacteria
- Pathogenic bacteria do not always infect the hosts of cells, they can remain within body cavities or spaces
- Toxins produced by the bacteria also damage cells
- They are small and can reproduce very quickly
- Bacterial infections include:
- M. tuberculosis causes tuberculosis (TB) in humans
- N. meningitidis causes bacterial meningitis in humans
- Helicobacter Pylori causes stomach ulcers
- V. Cholerae causes cholera in humans
Pathogenic fungi
- Fungal diseases are much more common in plants than animals
- Fungi can be single-celled or multicellular (with threads of hyphae)
- The spores they produce allow them to infect other organisms
- In plants, fungal diseases tend to be much more serious and can threaten entire crops
- Fungal diseases include:
- Cattle ringworm and athletes foot are fungal diseases in animals
- Black Sigatoka is a fungal disease in bananas
- Chalara Ash Dieback is a fungal disease that affects ash trees
Pathogenic protists
- Protists are a diverse group of eukaryotic (and usually unicellular) organisms
- They are parasites which means they need a host in order to survive
- Only a small number of protists are pathogenic, but the diseases they cause are often serious
- Examples of diseases caused by protists are:
- Plasmodium falciparum is a protist that causes severe forms of malaria in humans
- P. infestans causes the infamous potato blight
