Chapter 12 - Communicable Diseases Flashcards
What is a pathogen
An organism that can produce a disease
What is a vector
They carry the pathogens from one organism to another. Ex: wind or water
What are the 4 types of pathogens
Bacteria, viruses, protoctista and fungi
Bacteria as a form of pathogen
They can be classified using either the cell walls or the shape.
What is rod shaped bacteria called
Bacilli
What is spherical shaped bacteria called
Cocci
What is comma shaped bacteria called
Vibrios
What is spiralled shaped bacteria called
Spirilla
What is corkscrew shaped bacteria called
Spirochaetes
How can you use a bacteria’s cell walls to differentiate between bacteria
Gram staining.
Can see how bacteria will react to different antibiotics.
Viruses as a form of pathogen
They invade cells, then take over the genetic material and produce more viruses. They can attack bacteria as well, which are called bacteriophages. They destroy the cells.
Protoctista as a form of pathogen
They are a group of eukaryotic organisms with a wide variety of feeding mechanisms. A small % of them act as pathogens and enter through ex. malaria or infected water.
Fungi as a form of pathogen
They attack more plants rather than animals. Eukaryotic organisms can kill leaves, and prevent plants from photosynthesising. As fungi reproduces, they spread over distances.
What are the modes of action
Damaging the host tissue directly.
Or producing toxins which damage host tissues.
Ways to damage the host tissue directly
The viruses can take over the cell metabolism and insert its DNA and make new viruses, then burst to destroy the cell and continue.
Protoctista can break the cell open as new generation emerge. They dont take over the cell’s DNA.
Fungi digest living cells.
Ways to produce toxins which damage the host tissues
Most bacteria produce toxins to the hosts’ cells and damage the cell membrane, or DNA.
Toxins are by-products of normal functioning bacteria
Some fungi can also do this
Ring Rot - plant disease
A bacterial disease of potatoes, tomatoes, and aubergines.
Caused by Gram positive bacteria
Damages leaves, fruits and tubers.
Means the plants can’t be used in field for at least 2 years.
TMV - plant disease
Infects tobacco plants And tomatoes, peppers etc. No cure (but can be resistant) Damages leaves, flower, fruits and stunts growth. Leads to total crop loss
Potato blight - plant disease
A fungus- like protoctista.
No cure (but can be resistant)
Destroys leaves, fruits and tuber
Black Sigatoka - Plant disease
Banana disease Hyphae penetrates cell and digests them. Can cause 50% reduction in yield No cure (but can be controlled) Attacks and destroys the leaves The leaves then turn black.
TB- Animal Diseases
A bacterial disease
Destroys lung tissues and suppresses the immune system
People affected by AIDS/HIV are much more likely to develop TB.
It is curable and preventable.
Bacterial meningitis- Animal Disease
A bacterial infection of meninges of the Brain.
It can spread and cause blood poisoning and lead to rapid death.
Mainly affects teenagers.
If there is a purple rash that won’t leave when glass is pressed against it, that is a symptom.
Antibiotics can cure it.
HIV/AIDS - Animal diseases
They target “T Helpers” in the immune system, until the entire immune system is destroyed. HIV is a retrovirus with RNA as its genetic material. It contains the enzyme reverse transcriptase, which transcribes the RNA to a single strand of DNA.
It spread by sharing needles, and bodily fluids.
There is no vaccine and no cure, but antiretroviral drugs can reduce the impacts.
Influenza - Animal diseases
A viral infection of the ciliated epithelial cells in the gas exchange system. By killing them, it leaves the airways open to another infection. Sometimes, there can be a major change in the surface antigens, starting a pandemic, as there are no antibodies available.
Malaria - Animal diseases
Caused by a protoctista, spread by mosquitoes.
The female mosquito needs 2 blood meals to provide her with protein before she lays her eggs.
It invades the red blood cells, liver and the brain.
There is no vaccine, and the only option is to control the vector.
Ring worm - Animal diseases
A fungal disease which affects dogs, cattle and humans.
It causes grey, crusty circular areas on the skin. Antifungal creams can help.
Athlete’s Foot - Animal diseases
Human fungal disease
Causes cracking, scaling and antifungal creams can help.
What are the 2 ways that a communicable disease can spread between animals
Direct and indirect
Examples of direct contact between animals
Kissing
Sexually transmitted disease
Direct skin contact
Examples of inoculation between animals
Break in the skin
Animal bites
Sharing needles
What does direct contact between animals include
Inoculation
Ingestion
Direct contact
What does indirect contact between animals include
Fomites
Droplet inhalation
Vectors
Examples of fomites
Inanimate objects (sharing socks)
Examples of vectors between animals
Water
Other animals
Factors that affect the transmission of communicable disease
Overcrowded living Poor nutrition Having immunosuppresants A poor immune system. Poor disposal of waste Climate change (new vectors) Culture and infrastructure (traditional medical practices) Socioeconomic factors (Lack of trained workers)
Indirect transmission of communicable disease in plants
Soil contamination
Infected pants can leave bacteria or viruses in the soil
Vectors in transmission of communicable disease in plants
Wind
Water
Animals
Humans
Factors affecting transmission of communicable disease in plants
Planting crops that are vulnerable to disease overcrowding Poor mineral nutrients Damp, warm conditions Climate change (more rainfall and wind)
What are some easy ways to prevent pathogens from getting into plants?
thick waxy cuticle
bark
cellulose cell walls
This is all because plants don’t heal diseased tissues. They just seal it and then sacrifice it.
How can plants recognise the attack
The molecules in the pathogens (or any chemical enzymes secreted by the pathogens) are detected by the receptors in the cell. Then, this triggers the release of molecules that switch on genes in the nucleus. This means that any of the defences are set up.
What is the main plant physical defence
Producing high levels of callose. This is a carbohydrate molecules, which has 1-3 and 1-6 bonds.
What are all the physical plant defences
In minutes of an attack, plants gather callose at the area of infection by the pathogen to create a barrier.
Lignin also gather to add extra strength.
Callose gathers and blocks sieve plates too, to prevent spreading.
Callose is deposited in the plasmodesmata between infected cells and their neighbours.
What are the plant’s chemical defences
Insect repellent Insecticides Antibacterial compounds Antifungal compounds Anti-oomyceles (eg. glucanase) General toxins (cyanide)
How can the body keep out pathogens
Skin Healthy microorganisms Sebum Lined by mucous membranes Phagocytes Lysosomes in tears and urine Acid in stomach Sneezes and coughs Vomiting and diarrhoea.
How does blood clotting help keep pathogens out of the body
If you cut yourself, blood clots to seal the wound. As blood platelets come into contact with the collagen in your skin, they begin to secrete 2 chemicals.
They are: thromoplastin and serotonin
Thromoplastin
Results in the formation of blood clotting
Serotonin
They narrow and reduce the supply of blood to the area.
Wound repair
- A hard scab is formed.
- Epidermis cells below the scab starts to grow.
- Sealing the wound permanently
- Damaged blood vessels begin to regrow.
- Collagen fibres are deposited to give strength
- When the epidermis reaches a normal thickness, the scab is healed and it peels off.
Inflammatory response includes what
Mast cells are activated in the damaged tissues so that they can inflame.
It includes:
Histamines and cytokines
Histamines (Inflammatory response )
Makes the blood vessels dilate, which causes redness and heat.
Heat prevents the pathogens being produced.
It makes the blood vessels’ walls more leaky.
So blood plasma is forced out as is called tissue fluid.
This causes pain and swelling.
Cytokines (Inflammatory response )
Attracts phagocytes to the site to engulf pathogens
How does the body respond to get rid of pathogens (main list)
Fevers
Phagocytosis
Macrophages
Chemicals
Explain fevers (How does the body respond to get rid of pathogens)
Most pathogens reproduce best at temperature below 37 degrees.
So, the specific immune system works faster at higher temperatures.
Explain phagocytosis (How does the body respond to get rid of pathogens)
- Pathogens produce chemicals that attract phagocytes.
- Phagocytes recognise non-human proteins and it engulfs the pathogen and enclosed it in a vacuole called phagosome.
- The phasosome combines it with a lysosome to form a phagolysosome.
- The pathogen is digested and destroyed.
Explain Macrophages (How does the body respond to get rid of pathogens)
It digests the pathogens by combining its antigens from the pathogen surface membrane with special glycoproteins called Major Histocompatibility complex.
The complex moves these pathogens’ antigens to the macrophages’ own surface membrane, called an antigen-presenting cell.
The antigens now stimulate other cells involved in the specific immune system.
Explain Chemicals (How does the body respond to get rid of pathogens)
Phagocytes produce cytokines when they have engulfed pathogens.
They inform other phagocytes that the body is under attack, they also increase the body temperature.
Opsonins bind to pathogens and ‘tag them’ so they can be easily recognisable to phagocytes.
Phagocytes have receptors on their cell membranes that bind to common opsonins.
