B3-Infection and Response

What is a communicable disease

a disease which can be spread

What is bacteria

• very small cells (hundredth of a human body cell) reproduce in the body
• produces toxins which damage cells and tissue

What is a virus

• A virus is not a cell they’re tiny about 1/100th of a bacterium reproduce in the body
• Live inside hosts cells using cell machinery to create copies until cell bursts letting out more of the virus
• This is what makes you feel ill

Protists

• Eukaryotes, mostly single celled
• Some are parasites live on or in organisms and can cause damage
• Often transferred by a vector which isn’t affected by the protist- e.g. malaria mosquitos

Fungi

• Some single celled
• others have a body made of hyphae (thread like structures)
• These hyphae can grow and penetrate the human skin and surface of plants

How can pathogens be spread?

• water- drinking dirty water e.g. cholera spread by drinking diarrhoea water of other cholera infected people
• air- Carried in the air then breathed in, carried by air droplets produced from coughs and sneezes e.g. influenza virus causing flu is spread this way
• direct contact- by touching contaminated surfaces including skin e.g. athlete’s foot is a fungus which makes skin itch and fall off spread through contact with shower floors, towels etc.

What 3 viral diseases do you need to know?

• Measles

- spread by droplets from an infected person’s sneeze/cough

• HIV

  - spread by sexual contact or by exchanging bodily fluids such as blood which could happen if people share needles when taking drugs.

• Tobacco Mosaic Virus

-a virus that affects species of plants such as tomatoes

What are the symptoms of measles

Measles- is a viral disease spread by droplets from an infected person’s sneeze or cough

symptoms include:

-red skin rash

-signs of fever ( high temp)

-can cause pneumonia (lung infection)

-or even inflammation of the brain (encephalitis)

• This means it can be fatal but most people are vaccinated against measles when they are young in the UK

What do we need to know about HIV

HIV- a virus spread by sexual contact or exchange of bodily fluids such as blood

• initial flu like symptoms for a few weeks (Usually this person doesn’t feel any symptoms for several years)
• during this time HIV can be controlled by antiretroviral drugs which stop the virus from replicating in the body
• the virus attacks immune cells
• If the body’s immune system is badly damaged it can’t cope with other infections or cancers, AKA late stage HIV or AIDS

What do we need to know about Tobacco Mosaic Virus (TMV)

Tobacco Mosaic Virus- the virus causes a mosaic pattern on the leaves of the plant- parts of the plant become discoloured

• The discoloration means the plant can’t carry out photosynthesis as well, so the virus affects growth

What Fungal Disease do we need to know about

Rose black spot- a fungus that causes purple or black spots to develop on the leaves of rose plants, spread through the environment in water or wind

• leaves can then turn yellow and fall off
• Meaning less photosynthesis can happen so the plant doesn’t grow properly
• Gardeners can treat the disease by using fungicides and stripping the plant of affected leaves

What disease is caused by a protist?

Malaria- spread by mosquitos (vectors)

• Picked up by mosquitos when they feed on an infected animal
• then every time a mosquito feeds on an animal they are infected by inserting the protist into the animals blood vessels
• Malaria causes repeated fever and can be fatal
• Spread reduced by stopping mosquitos from breeding lowering mosquito population
• People can be protected from mosquitos by using insecticides and mosquito nets

what is Salmonella

Salmonella- A type of bacteria that causes food poisoning

• Infected people can suffer from fever, stomach cramps, vomiting and diarrhoea
• Caused by toxins that bacteria produce
• Salmonella can be caught by eating food that’s been contaminated with salmonella bacteria e.g. eating chicken that caught salmonella before it died or eating food which has been contaminated while being prepared
• In the UK most poultry is given a vaccination against Salmonella. this is to control the spread of the disease

What is Gonorrhoea

Gonorrhoea- a sexually transmitted disease

• STDs are passed by sexual contact e.g. having unprotected sex
• Gonorrhoea is caused by bacteria
• A personal with gonorrhoea will get pain when they urinate. Another symptom is a thick yellow or green discharge from the vagina or penis
• Originally treated by an antibiotic called penicillin but it is now more difficult to treat as strains of the bacteria have become resistant to it.
• To prevent the spread of gonorrhoea, people can be treated with antibiotics and should use barrier methods of contraception, such as condoms

How can the spread of disease be reduced or prevented

• Being hygienic- Washing hands before preparing food or after you’ve sneezed
• Destroying vectors- getting rid of organisms that spread disease preventing the disease from being passed on e.g. insects which act as vector can be killed by insecticides or by destroying their habitat
• Isolating infected individuals- If you isolate someone who has a communicable disease, it prevents them from passing it on to anyone else.
• Vaccination- Stops animals and humans from developing the infection and passing it on to someone else

What defence systems does the body have

• skin acts as a barrier to pathogens. It also secretes antimicrobial substances which kill pathogens
• Hairs and Mucus in your nose trap particles that could contain pathogens
• The trachea and bronchi secrete mucus to trap pathogens.
• Lined with cilia. There are hair-like structures, which waft the mucus up to the back of the throat where it can be swallowed
• The stomachs hydrochloric acid kills pathogens that make it that far from the mouth
• If pathogens do make it past all of that your immune system kicks in to fight it most importantly the white blood cells

What are the white blood cells 3 lines of attack

1. Consuming them- white blood cells can engulf foreign cells and digest them. This is called phagocytosis
2. Producing Antibodies- Every invading pathogen has unique molecules (called antigens) on its surface.

• When some types of white blood cell come across a foreign antigen they will start to produce proteins and antibodies to lock onto the invading cells so they can be found and destroyed by other white blood cells.

• The antibodies produced are specific to that type of antigen.

• Antibodies are then produced rapidly and carried around the body to find all similar bacteria or viruses

• If the person is infected again the white blood cells will rapidly produce the antibodies to kill it- the person is naturally immune to the pathogen and won’t get ill

• White blood cells that produce antibodies are known as B-lymphocytes

  3. Producing antitoxins- These counteract toxins produced by the invading bacteria.

What does a vaccination contain

Vaccinations involve injecting small amounts of dead or inactive pathogens. These carry antigens, which cause your body to produce antibodies to attack them- even though the pathogen is harmless (since it’s dead or inactive). For example, the MMR vaccine contains weakened versions of the viruses that cause measles, mumps and rubella( German measles) all in one vaccine.

Why is a vaccine effective

If live pathogens of the same type appear after receiving the vaccine with the inactive pathogen in it the white blood cells can rapidly mass-produce antibodies to kill off the pathogen

Pros to vaccination

• Help control lots of communicable diseases that were once common in the UK ( e.g. polio, measles and mumps). Smallpox no longer occurs and polio infections have fallen by 99%
• Big outbreaks of the disease-called epidemics- can be prevented if a large percentage of the population is vaccinated. That way, even the people who aren’t vaccinated are unlikely to catch the diseases because there are fewer people able to pass it on.

Cons of vaccination

• Vaccines don’t always work- sometimes they don’t give you immunity
• You can sometimes have a bad reaction to a vaccine( e.g. swelling, or maybe something more serious like a fever or seizures). But bad reactions are very rare.

What do painkillers (e.g. aspirin) do

Reduce symptoms of pathogens don’t actually kill them

What do antibiotics (e.g. penicillin) do

They kill bacteria and there are different antibiotics for different bacteria

why don’t antibiotics work on viruses

Because they use your body cells to reproduce so its very difficult to develop drugs which kill the virus which out killing your body cells

How can bacteria become immune to an antibiotic

By mutating

How do resistant strains of bacteria multiply

The non resistant bacteria is killed off by the antibiotic but then the resistant bacteria is left on its own and reproduces creating more of the resistant strain. (This is an example of natural selection)

What could happen to the body if there was a resistant strain

It could cause a serious infection which can’t be treated by antibiotics e.g. MRSA (meticillin-resitant Staphylococcus aureus) causes serious wound infections and is restant to meticillin a powerful antibiotic

How can the rate of development of resistant strains be reduced?

doctors should avoid overprescribing antibiotics and you should finish the whole course of antibiotics rather than stopping when you feel better

Where did many drugs originally come from?

plants

Where did aspirin come from

a chemical found in willow

where did digitalis (treats heart conditions) come from

Developed from chemicals in foxgloves

What drug was extracted from microorganisms

Penicillin by Alexander flemming who found mold which was resitant to bacteria.

Where are drugs made now

Synthesised by chemists in labs

What is the first step in preclinical testing

Testing on human cells and tissues

What is the seconds step in preclinical testing

Live animals this is to test efficacy, its toxicity and the correct dosage. It must be tested on two different live mammals as part of British law

What is efficacy

Whether the drug works and produces the desired effect

What is toxicity

How harmful it is

What is dosage

The concentration that should be given, and how often it should be given

What is stage 3 of testing

Clinical trials- human testing

1. First it is tested on healthy volunteers to make sure it has no harmful side effects and given initially in low dosage which gradually increases.
2. Then it is given to those suffering from the illness and the optimum dose is found- the most effective with the least amount of side effects
3. To test how well the drug works the patients are split into two groups both told they are given the drug although only one group is given the drug the other is given a placebo ( a substance that looks like the drug but has no effect) which causes the placebo effect where patients believe the treatment will work so feel better even though it is doing nothing.
4. The clinical trials are blind so the patient doesn’t know whether they have a drug or placebo and is often double blind where the doctor doesn’t know until all the results have been gathered in order to prevent subconscious influence.
5. It is then peer reviewed to prevent false claims.