Pathogens

Types of Pathogens

Pathogens are microorganisms that cause communicable diseases. Bacteria, viruses, protists and fungi are all types of pathogen.

Bacteria:

• Small prokaryotic cells that can infect both plants and animals.
• Reproduce rapidly in optimum conditions (favourable temperatures, moisture levels and amounts of nutrients).
• Release toxins that damage cells and tissues and makes the infected organism suffer symptoms and feel unwell.
• They are not always harmful and can actually be useful e.g. bacteria found in the large intestines of some animals digest cellulose from food so its products can be absorbed into the blood and used around the body.

 

Viruses:

• They are not cells and are not classified as living organisms because they rely on host cells to survive and reproduce.
• They insert their genetic material into the cells of the infected organism and use the cells’ machinery to reproduce rapidly.
• This can cause the cells to burst, release more viruses that cause further infections in the body and damage the initial infected cell. It is this cell damage which will make the host feel unwell.

 

Protists:

• Eukaryotic organisms that are often single-celled.
• They can be parasitic which means they live on or in a host organism and cause them damage.
• They are often transferred between hosts by organisms that don’t get the disease itself, called vectors. 

 

Fungi:

• Grow on living tissues and can be either single-celled, like yeast, or have a body made of hyphae.
• Hyphae penetrate living tissues, causing infections, and produce spores which allow infections to be spread to other organisms.
• Fungal infections are most common in plants where they destroy whole crop fields but a few can infect animals, e.g. athletes foot.

 

You should be able to name examples of diseases from each category, state how they are spread between organisms and explain how they can be prevented and treated.

Spread of Pathogens

Communicable diseases are spread between organisms in a number of different ways:

• Air– some pathogens can be found in droplets from coughs and sneezes that are carried through the air and breathed in by other organisms/humans, e.g. influenza.
• Water– some pathogens are found in dirty water and can be picked up by drinking or bathing in it, e.g. cholera.
• Direct contact– some pathogens can be acquired by touching contaminated surfaces or skin, e.g. athletes foot.
• Vectors– pathogens can be transferred between organisms by vectors (organisms that carry the pathogen without getting the disease).

Preventing Disease

The spread of diseases can be prevented in different ways, depending on how the pathogen is spread:

• Keeping good hygiene will prevent the spread of certain diseases. The spread of airborne diseases can be prevented by catching sneezes and coughs in tissues instead of letting the pathogens travel in the air. Washing your hands regularly (before preparing food, after sneezing, after using the toilet etc.) can prevent the spread of diseases that are transmitted through direct contact.
• Diseases spread by direct contact and in the air can also be prevented by isolating the diseased individual.
• The spread of vector-borne diseases can be prevented by killing the vectors carrying the disease using insecticides or preventing them from breeding by destroying their habitats.
• Vaccinations prevent diseases spreading as they stop people and animals from being able to develop the disease and therefore pass it on to others.