2.2 Communicable Disease 1 - Introduction Flashcards
What are pathogens?
Pathogens are microorganisms that cause communicable diseases. There are 4 types
What are the 4 types of pathogens?
- Bacteria
- Viruses
- Protists
- Fungi
What are the 7 different ways that pathogens can infect animals and plants?
- Water
- Air
- On surfaces
- Body fluids
- Animal vectors
- Soil
- Food
How do pathogens spread through the air? (2)
- Some pathogens are carried in the air. There’s a type of fungus that infects ash trees and causes Chalara ash dieback disease. It is transmitted from infected plants, through the air, by the wind
- Airborne pathogens can be carried in droplets produced when you cough/sneeze - so other people can breathe them in. E.g. the influenza virus that causes flu is spread this way
How do pathogens spread through contaminated food and water? (2)
- Some pathogens are picked up by eating contaminated food. E.g. Salmonella bacteria are found in some foods, e.g. raw meat. If these foods are kept too long or not cooked properly the bacteria can cause food poisoning
- Some pathogens are picked up by drinking contaminated water. E.g. cholera can be spread by drinking water that has been contaminated by the diarrhoea of someone already suffering from cholera
How are pathogens spread on surfaces? (2)
- Some pathogens can be picked up by touching contaminated surfaces. E.g. tobacco mosaic disease affects many species of plants, e.g. tomatoes. It is caused by a virus called tobacco mosaic virus (TMV) that makes the leaves of plants mottled and discoloured. The discolouration means the plant cant photosynthesise as well, so the virus affects growth.
- Athlete’s foot is a fungal disease which affects humans - it makes skin on the feet itch and flake off. It’s most commonly spread by touching the same things as an infected person, e.g. shower floors and towels
How can we stop communicable diseases spreading? (4)
- Hygiene: washing hands, cleaning cookery items
- Killing the vectors (organisms that transport the pathogen): mosquitoes OR spreading insecticides (chemicals which kill insects)
- Vaccinations: If you cant catch a disease in the first place, you cant pass it on
- Isolate or quarantine: no contact
How can pathogens spread by body fluids?
- Some pathogens are spread by bodily fluids such as blood (e.g. by sharing needles to inject drugs or by contaminated blood transfusion), breast milk (through breast feeding) and semen (through unprotected sex - diseases that are spread through sexual contact are known as STIs).
- HIV is a virus spread by exchanging body fluids. It initially causes flu-like symptoms for a few weeks, but after that, the person doesn’t usually experience any symptoms for several years. The virus enters the lymph nodes and attacks the immune cells. If the immune system isn’t working properly, it cant cope with other infections or cancers. At this state, the virus is known as late state HIV, or AIDS
How can pathogens be spread by animal vectors?
- Animals that spread disease are called vectors. E.g. malaria is caused by a protist. Part of the malarial protist’s life cycle takes place inside a mosquito. Mosquitoes act as vectors - they pick up the malarial protist when they feed on an infected animal. Every time the mosquito feeds on another animal, it infects it by inserting the protist into the animal’s blood vessels. Malaria causes repeating episodes of fever. It can be fatal
How can pathogens be spread by soil?
- Some pathogens can live in the soil, so plants in the contaminated soil may be infected. E.g. the bacteria, Agrobacterium tumefaciens, that causes crown gall disease, are able to live freely on some soils and on the roots of some plants. If the bacteria enter a plant, they can cause the growth of tumours called galls on the roots, stems and branches. The galls can damage the plant tissues, restricting the flow of water through the plant. This causes the plant to become weaker and it may eventually die
Why is HIV dangerous?
It can suppress the immune system and makes people more susceptible to catching other infectious diseases
What is bacteria?
Very small cells (about 1/100th the size of your body cells), which can reproduce rapidly. They make you ill by producing toxins (poisons) that damage your cells and tissues
What are viruses?
They are not cells. They’re really small, about 1/100th the size of a bacterium. They replicate themselves inside the infected organism’s cells. These cells then burst, releasing the viruses
What are protists?
These are eukaryotic, usually single-celled and vary in size
What is fungi?
Some fungi are single-celled while others have a body, which is made up of thread-like structures called hyphae. These hyphae can grow and penetrate human skin and the surface of plants, causing diseases. They can also produce spores, which can be spread to other plants and animals
