Preventing and treating disease
Preventing and treating disease
Immunisation involves giving a vaccine made of a dead or inactivate form of a disease-causing microorganism. Stimulating you body's natural immune response to invading pathogens
A small amount of the dead or inactive pathogens is introduced into your body > Stimulates white blood cells to produce antibodies needed to fight the pathogen and prevent you from getting ill. The if you meet the same live pathogen your white blood cells can respond rapidly and make the right antibodies to fight the disease.
Doctors use vaccines to protect us against bacterial diseases (eg tetanus and diphtheria) and viral diseases (eg Polio, measles, mumps and rubella)
Smallpox has been completely wiped out by vaccinations
Large population vaccinated/ immune= Spread of pathogen reduced and disease may even disappear- This is known as herd immunity
If the number of people taking vaccines falls the herd immunity is lost and a disease can reappear
An example being whooping cough. In the UK 1970s there was a scare that the whooping cough vaccines weren't safe. Vaccination rates fell from over 80% to 30%. In the following years thousands of children got whooping cough. People began to realise the vaccine was safe and herd immunity was effective again.
Every cell has unique proteins on its surface called antigens
Antigens on microorganisms that enter the body are different and your immune system recognizes this.
White blood cells make specific antibodies which join up with the antigens and inactivate or destroy the particular pathogen
White blood cells need to remember the right antibody needed to destroy a particular pathogen. If the cells meets it again the memory cells can make the same antibody very quickly and kill the pathogen so you are immune to the disease
Meaning the first time you meet a pathogen you become ill as there is a delay in making the antibody needed.
Antibiotics and painkillers
Treating the symptoms
Aspirin and paracetamol are useful painkillers. If you have a cold it will relieve the symptoms (eg sore throat, head ache) However they have no effect on a viral infection that has entered your tissue and made you feel ill
Many painkillers relieve symptoms but don't kill the pathogens. You have to wait for your immune system to overcome the pathogens before you can get well again
Antibiotics- Drugs to cure bacterial diseases
Antiseptics and disinfectants are used to kill bacteria outside the body but they are very dangerous to use inside your body. Aswell as killing the pathogens they would kill you too.
Antibiotics have changed the treatment of communicable diseases. They work inside your body to kill bacterial pathogens. The impact of antibiotics on deaths has been huge. E.g infections from women giving birth decreased dramatically.
How antibiotics work
Antibiotics (eg penicillin) work by killing the bacteria that cause disease whilst they are inside your body. They damage the bacterial cells without harming your own cells
Antibiotics can be taken in the form of a pill or syrup if you are really ill then it can be put straight into your bloodstream making sure they reach the pathogens in your cells as quickly as possible
Some antibiotics kill a wide range of bacteria, others are very specific and only work against particular bacteria.
Antibiotics cannot kill viral pathogens so they have no effect on diseases caused by viruses.
A virus reproduces inside the cells of your body making it extremely difficult to develop drugs that will kill the viruses without damaging the cells and tissues of your body at the same time.
Strains of bacteria that are resistant to antibiotics are evolving meaning antibiotics which used to kill a particular type of bacteria no longer have an affect > they can't cure the disease.
Some types of bacteria are resistant to all known antibiotics causing great concern if new antibiotics can't be found to cure bacterial diseases
Developing and testing a new drug
It can take up to 12 years to bring new medicine into works due to meeting all the required conditions
Researchers target a disease and make lots of possible new drugs. These are tested in the lab to find out if they are toxic or not and how efficient they are.In the lab they are tested on tissue, cells and even whole organs. Many fail at this stage.
The small number of chemicals which pass the earlier test are then tested on animals in the lab, to find out how they work in a living organism. Provides information about possible side effects and doses.
Preclinical testing takes place in the lab using cells, tissues and live animals.
Clinical trails use healthy volunteers and patients. Low doses are given to healthy people to check for side effects. If it is found to be safe it is tried on a small number of patients to see if it treats the disease. If it is safe and effective, bigger clinical trials take place to find out the maximum dosage
The medicine needs to pass legal tests, so it is licensed and your doctor can prescribe it
A good medicine is:
Effective- it must prevent or cure a disease or at least relieve symptoms
Safe- the drug must not be too toxic or have unacceptable side effects for the patient
Stable- you must be able to use the medicine under normal conditions and store it for some time
Successfully taken into and removed from your body- it must reach its target and be cleared from your system once it has done its work
Double blind trials
Evaluates effectiveness of the new medicine. A group of patients with the target disease agree to take part in the trials. Some are given a placebo that doesn't contain the drug and some are given the medicine. Patients are randomly allocated to the different groups. Then neither the doctors nor the patients know who has received the real drug or the placebo until the trail is over.
The patients health is monitored carefully
Often the placebo will contain a different drug that is already used to treat the disease. Patient is not deprived of treatment during the trail
The results or drug tests and trails are published in journals after they have been scruntinised in a process of peer review
Other scientists working in the same area can check the results over, helping to prevent false claims
New medicines are being developed all the time by scientists and doctors to try to find new ways of curing more diseases. Testing new medicines in a lab.
Drugs from microorganisms- discovering penicillin
Alexander Fleming was growing bacteria for study purposes. He was careless and left the lid of his culture plate. After a period of time he saw that his culture plates had mould on them and realized something had killed the bacteria covering the gel.
He recognized the importance of his discovery and called the substance that killed the bacteria 'penicillin' .
!0 years after the discovery Chain and Florey set about trying to extract penicillin and they succeeded. They gave some penicillin to a patient dying of blood infection and he almost recovered. Until the penicillin ran out
Eventually Florey and Chain made penicillin on an industrial scale, producing enough to supply the demands of WW1. It is still used today.
Drugs from plants
Number of drugs used today based on traditional medicines extracted from plants
Digitalis and digoxin are two of several drugs extracted from foxgloves. They have been used since the 18th century to help strengthen the heartbeat Although there are lots of modern drugs these are still used today by doctors
The painkiller aspirin originates from a compound found in the bark of willow trees.The anti-flammatory and pain- relieving properties were first recored in 400BC. Aspirin is still commonly used to treat a wide range of health problems
Medicines for the future
Finding new medicines isn't easy as it's hard to find chemicals that kill bacteria without damaging human cells. Drugs are now synthesised by research chemists working in pharmaceutical industry using chemical banks and computer models.
Starting point may still be a chemical extracted from a plant or micro organism. Compounds showing promise as antibiotics can be modified to produce more powerful molecules that can be synthesised easily and cheaply.