Chapter 12-12.7- Preventing and treating disease Flashcards
What are non-communicable diseases?
Non-communicable diseases cannot be passed from one person to another. They include heart disease, most types of cancer and many diseases of the nervous system, endocrine and digestive system.
Communicable diseases are caused by pathogens and can be passed form person to person.
When you come into contact with a foreign antigen, you need some form of immunity to prevent you getting the disease. There are several ways of achieving this immunity.
What is natural immunity?
Some forms of immunity occur naturally in the body.
- When you meet a pathogen for the first time, your immune system is activated and antibiotics are formed, which results in the destruction of the antigen. The immune system produces T and B memory cells so if you meet a pathogen for a second time, your immune system recognises the antigens and can immediately destroy the pathogen, before it causes disease symptoms. This is known as natural active immunity. It is known as active because the body has itself acted to produce antibodies and/or memory cells.
- The immune system of a new-born baby is not mature and it cannot make antibodies for the first couple of months. A system has to protect the baby for those first few months of life. Some antibodies cross the placenta from the mother to her fetus while the baby is in the uterus, so it has some immunity to disease at birth.
The first milk a mammalian mother makes is called colostrum, which is very high in antibodies.
The infant gut allows the glycoproteins to pass into the bloodstream without being digested. So within a few days of birth, a breast-fed baby will have the same level of antibody protection against disease as the mother.
This is natural passive immunity and it lasts until the immune system of the baby begins to make its own antibodies.
The antibodies the baby receives from the mother are likely to be relevant to pathogens in its environments, where the mother acquired them.
What is artificial immunity?
Some diseases can kill people before their immune system makes the antibodies they need. Medical science can give us immunity to some of these life-threatening diseases without any contact with live pathogens.
What is artificial passive immunity ?
For certain potentially fatal diseases, antibodies are formed in one individual (often an animal) , extracted and then injected into the bloodstream of another individual. This artificial passive immunity gives temporary immunity- it doesn’t last long but it can be lifesaving.
For example, tetanus is caused by a toxin released by the bacterium Clostridium tetani, found in soil and animal faeces. It causes the muscles to go into spasm so you cannot swallow or breathe.
People who might be infected with tetanus (for example after a contaminated cut) will be injected with tetanus antibodies extracted from the blood of horses, preventing the development of the disease but not providing long-term immunity.
Rabies is another fatal disease that is treated with a series of injections that give artificial passive immunity.
What is artificial active immunity? - the principle of vaccination
In artificial active immunity the immune system of the body is stimulated to make its own antibodies to a safe form of an antigen ( a vaccine). which is injected into the bloodstream (vaccination).
The antigen is not usually the normal live pathogen, as it could cause the disease and have fatal results.
What are the main steps of artificial active immunity ?
1) The pathogen is made safe in one of a number of ways so that the antigens are intact but there is no risk of infection.
2) Small amounts of the safe antigen, known as the vaccine, are injected into the blood.
3) The primary immune response is triggered by the foreign antigens and your body produces antibodies and memory cells as if you were infected with a live pathogen.
4) If you come into contact with a live pathogen, the secondary immune response is triggered and you destroy the pathogen rapidly before you suffer symptoms of the disease.
The artificial active immunity provided by vaccines may last a year, a few years or a lifetime. Sometimes boosters (repeat vaccinations) are needed to increase the time you are immune to a disease.
What might vaccines contain?
Vaccines may contain:
- Killed or inactivated bacteria and viruses, for example, whooping cough (pertussis)
- Attenuated (weakened) strains of live bacteria or viruses, for example rubella, BCG against TB, polio (vaccine taken orally)
- Toxin molecules that have been altered and detoxified, for example diphtheria, tetanus
- Isolated antigens extracted from the pathogen, for example, the influenza vaccine
- Genetically engineered antigens, for example, the hepatitis B vaccine
Why are vaccines used?
Vaccines are used to give long term immunity to many diseases. However, they are also used to help prevent epidemics.
At the beginning of an epidemic, mass vaccination can prevent the spread of the pathogen into the wider population. When vaccines are being developed to prevent epidemics, they often have to be changed regularly to remain effective.
When a significant number of people in the population have been vaccinated, this gives protection to those who do not have immunity.
This is known as herd immunity, as there is minimal opportunity for an outbreak to occur.
What is an epidemic?
An epidemic is when a communicable disease spreads rapidly to a lot of people at a local or national level.
What is a pandemic?
A pandemic is when the same disease spreads rapidly across a number of countries and continents.
What are 2 examples of communicable diseases that cause problems at a global level but cannot be prevented by vaccination?
Malaria-
Plasmodium, the protoctist that causes malaria. It is very evasive- it spends time inside the erythrocytes so it protected by self antigens from the immune system, and within an infected individual its antigens reshuffle.
HIV, the human immunodeficiency virus that causes AIDS. It enters the macrophages and T helper cells, so it has disabled the immune system itself.
So far scientists have been unable to develop a vaccine for these diseases, which between them affect millions of people globally every year.
How can medicine be used for the management of communicable diseases?
Medicine can be used to treat communicable and non-communicable diseases. Medicine can be used to treat symptoms and cure them, making people feel better.
Common medicines include painkillers, anti-inflammatory and anti-acid medicines (which reduce indigestion).
Medicines that cure people include chemotherapy against some cancers, antibiotics that kill bacteria, and antifungals that kill fungal pathogens.
What is the source and action of penicillin?
Source:
Commercial extraction originally from mould growing on melons.
Actions:
Antibiotics- the first effective treatment against many common bacterial diseases
What is the source and action of docetaxel/ paclitaxel?
Source:
Derived originally from yew trees
Action:
Treatment of breast cancer.
What is the source and action of aspirin?
Source:
Based on compounds from sallow (willow) bark
Action:
Painkiller, anti-coagulant, anti-pyretic (reduces fever) and anti-inflammatory
