1. What is a healthy organism?
1.1 Discuss the difficulties of defining the terms ‘health’ and ‘disease’
Health: a state of physical, mental and emotional well-being, not just an absence of disease
Disease: any condition that impairs or has the potential to impair, normal functioning.
Problems with these definitions:
• The definitions are broad and imprecise
• Used differently with common usage
• Hard to say whether conditions such as short sightedness and injuries (eg broken bones) are diseases
• Old age- what is healthy for an old person may not be healthy for a young person- health is a relative term
• Health is a constantly changing state and is relative to others and ourselves over a period of time.
2. Over 3000 years ago the Chinese and Hebrews were advocating cleanliness in food, water and personal hygiene
2.1 Distinguish between infectious and non-infectious disease
Infectious disease: caused by a pathogen and able to be passed from one organism to another (contagious). Eg flu, glandular fever, chicken pox and cholera.
Non-infectious disease: not caused by a pathogen and not contagious. Eg Inherited- cystic fibrosis, asthma, haemophilia. Nutritional- heart disease, iron deficiency, obesity, anorexia. Environmental- skin cancer, lung cancer.
Difference: Infectious is caused by a pathogen and non-infectious is not. Infectious is contagious and non-infectious is not.
2.2 Explain why cleanliness in food, water and personal hygiene practises assist in control of disease
2.3 Identify the conditions under which an organism is described as a pathogen
A pathogen can be defined as any organism or infective agent that lives in or on another living organism and causes a disease. The pathogen must be under the right conditions to multiply and be transmitted.
2.A Identify data sources, plan and choose equipment or resources to perform a first-hand investigation to identify microbes in food or in water
• This experiment involved agar plates, an inoculating loop and a sample of food or water
• Firstly we sterilised the bench, we left one plate as a control
• We heated the inoculating loop in the bunsen burner to kill of any microbes and to prevent contamination
• The loop was wiped across the source
• The agar plate was opened only 45° and the plate was streaked. Streaking involves wiping across the agar then turning the plate then wiping again, to grow individual colonies and to spread them out
• It was then sealed with sticky tape and labelled (sealed to avoid spreading of microbes
• It was put in the incubator for 48hrs at 30°C
• Microbes reproduce in the right conditions: warmth, moisture and nutrients
• Colonies are distinguished by their size, shape, surface, profile and colour
• Bacterial colonies are quite small, shiny and coloured
• Fungal colonies are fluffy and quite large
• Important that you do not become infected and that the experimental material does not become contaminated with organisms other than those you are studying
• Sterile techniques are essential (validity, must come from source not contaminants)
• Must sterilise inoculating loop
• Open lid to 45°
• Don’t breath on the agar
• Wear gloves
• Sterilize bench
• Seal the agar plate and do not open it after
• Use streaking to get isolated colonies
• We use disposable agar plates so there is no risk of the pathogens spreading
• Wear protective clothing eg lab coat
• Wash and dry hands before leaving lab
- Never open agar plate after experiment has been set up
2.B Gather, process and analyse information from secondary sources to describe ways in which drinking water can be treated and use available evidence to explain how these methods reduce the risk of infection from pathogens
Understanding your water:
Coliforms: coliform bacteria are used as a scientific indicator of the cleanliness of the water and the possible presence of disease-causing micro-organisms.
Cryptosporidium and Giardia: there micro-organisms occur in the gut of infected warm blooded animals. They can be introduced into the water supply through dead animal carcasses and faeces.
Turbidity: is a measure of suspended material in water that may cause it to look muddy or discoloured
Colour: water should be virtually colourless
Chlorine: to ensure good quality drinking water, chlorine is added to kill bacteria that may be cause disease
Fluoride: small amounts of fluoride are added for dental health reasons in accordance to legislation
Aluminum, iron and manganese: these substances occur naturally in water at low levels and may be responsible for taste and staining problems with water.
Coagulation: A coagulant such as alum is added to the water to overcome the repulsion between the negative charges of the particles suspended in the water (meaning they repel each other) allowing suspended particles to form larger particles or floc.
Flocculation and Sedimentation: Flocculation (a slow stirring) speeds up the production of the floc. The larger particles sink to the bottom as sediment. Most micro-organisms in the water are attached to these particles thus the sludge contains many microbes.
Filtration: The finer particles remaining in the water are removed by filtration. This is most effective against protozoan’s (including cryptosporidium and giardia) and most bacteria, especially larger ones eg salmonella. The water sinks through a thick bed of sand and other mixed particle sizes. These filters are regularly backwashed to remove microbes.
Disinfection: chemicals are added to the water after filtration. Chlorine is usually added; this kills off bacteria eg Salmonella and cholera. It is not so effective against cryptosporidium, which may escape the filter due to its strong cyst walls. Chloroamination (chlorine and ammonia) is a more effective treatment. Boiling water is advised if cryptosporidium levels increase.
How these methods reduce the risk of infection:
• Chlorine added kills the bacteria no bacteria to cause infection
• Boiling kills of pathogens no pathogens to cause infection
• Distillation removes organic compounds no pathogens, chlorides or nitrates
• Sludge is removed this contains the microorganisms thus they are not there to cause infection
• Filtration removes bacteria and pathogens not there to create infection
3 During the second half of the nineteenth century, the work of Pasteur and Koch and other scientists stimulated the search for microbes as causes of disease.
3.1 Describe the contribution of Pasteur and Koch to our understanding of infectious diseases
Louis Pasteur 1825-1895-Germ theory of disease
• Pasteur discovered that most infectious diseases were caused by micro-organisms or germs
• He developed the swan necked flask which enabled him to show that microbes were present in air, thus disproving spontaneous generation.
• Bacteria was discovered in 1676 but were thought to be spontaneously generated (living coming from non-living)
• Pasteurisation: Pasteur also showed that the microbes spoiling wine could be killed by heating the wine to 55°C for several minuets. This led to the process now called pasteurization of milk which greatly reduces the bacteria in milk (72°C )
• Vaccination: Pasteur developed the technique of inoculating animals with a weakened form of the disease giving them protection against future infection eg sheep against anthrax.
Robert Koch 1843-1910
• Koch was the first person to develop a set of rules (postulates) which linked a particular organism with a particular disease
• He was the first to develop a way of growing pure cultures of bacteria on agar in a Petri dish.
• He stained, described and identified many bacteria including TB, cholera and anthrax.
• Koch laid down a set of conditions (postulates) which must be satisfied before it can be accepted that a particular bacteria causes a particular disease
1. Micro-organisms must be present in every case of the disease (COMMON)
2. Organism must be cultured and described (CULTURE)
3. Organism must produce the same symptoms when a pure culture is injected into a healthy host (CAUSE)
4. The same organism isolated originally must be re-grown from the animal in which the disease was induced and found to be the same (COMPARE)
3.2 Distinguish between the following and name one example of a disease caused by each type of pathogen.
– Prions – infectious agents that are made of proteins that are naturally occurring, do not contain DNA or RNA or nucleic acid. Example of disease: Kuru- pathogenic prion which causes uncontrollable shaking, constant trembling and grimacing and eventually death.
– Viruses – nucleic acid (DNA or RNA) within a protein shell or coat. Extremely small. infectious agent that can replicate only inside the cells of other organisms. Example of disease: chicken pox, common cold, AIDS (caused by HIV)
– Bacteria – singled celled organism with no nucleus. No membrane, prokaryotic cell. Present everywhere, can be beneficial. Example of disease: pneumonia, food borne illnesses eg caused by salmonella, tetanus, syphilis.
– Protozoans – member of protista kingdom. Single celled, eukaryotic ( includes nucleus and organelles). Larger than bacteria. Example of disease: the protozoan giardia- can cause diarrhoea, plasmodium falciparum- can cause malaria
– Fungi – large group of eukaryotic organisms that include micro-organisms such as yeast, moulds, mushroom. Heterotrophic-get food from plants and animals NOT photosynthesis. Example of disease: candida- thrush and mucous membrane infection, tinea- ringworm and athletes foot
– Macro-parasites – large enough to be seen with the naked eye. They grow in the host but multiply by producing infective stages that are released from the host, allowing the parasite to spread to other hosts. These generally include ticks, mites, nematodes, flatworms etc. Example of disease: can live inside the hosts body eg flatworms which can cause tapeworm disease and liver fluke disease. Can also live on the outside of the body and can act as vectors for diseases eg flea is a vector for the bacterium which causes the bubonic plague. Can cause plant diseases eg aphids, weevils and mites.
3.3 Identify the role of antibiotics in the management of infectious disease
Antibiotics are chemical substances which destroy bacteria or inhibit their growth. They target the bacteria without destroying the host. They are not effective against viruses (other types of antimicrobial drugs can kill viruses and fungi).
Mode of action: some antibiotics kill the microbe by destroying the cell wall eg Penicillin (discovered by Alexander Fleming in 1928)
Some inhibit protein synthesis, bacteria are unable to make essential compounds, resulting in the death of the cell)eg tetracyclines and streptomycin.
Others destroy the cell membrane thus effectively destroy the bacteria eg amphotericin
Broad spectrum antibiotics act against a wide range of bacteria.
3.A Perform an investigation to model Pasteur’s experiment to identify the role of microbes in decay
Aim: To model Pasteur’s experiment showing that the swan necked flask will remain uncontaminated while the other goes bad, because bacteria came from the air not the broth.
Hypothesis: That the broth in the swan necked flask will remain uncontaminated
1. Place 50ml of broth into each flask
2. Boil the broth in both flasks for 5mins with the coiled tube and stopper (swan neck) on one of the flasks, leave the other one open. Wear safety goggles
3. Leave one flask open and the other flask with the swan neck for one week
Conclusion: the hypothesis was correct, the broth in the swan necked flask stayed uncontaminated while the open flask went bad.
3.B Gather and process information to trace the historical development of our understanding of the cause and prevention of malaria
Malaria conclusion: The identification of the protozoa plasmodium in the stomach of mosquitoes by Ronald Ross in 1897 led to his description of the life cycle. Once the link between malaria , plasmodium and mosquitoes was established it was then possible to use preventative measures such as draining swaps, using insecticides and repellents and mosquito nets to prevent malaria. These measures are used along with anti-malarial drugs such as chloroquine which kill protozoa. A vaccine is still under development (not used)
3.C Identify data sources, gather processes and analyse information from secondary sources to describe one named infectious disease in terms of its:
– Cause: By a pathogen called Vibrio cholerae. The pathogen is a comma shaped bacteria. Lifecycle: direct lifecycle from one host to another straight away.
– Transmission: Food or water contaminated by faeces from a person infected by Vibrio Cholerae.
– Host response: Antibodies are produced to the toxin (produced by the bacteria) If you survive you are resistant to that strain of the bacterium but not others. Bacteria does not cause the disease, the toxin that is produced by the bacteria causes the disease.
– Major symptoms: Diarrhoea-loss of water and salts, inflamed bowel, leads to muscle cramps (due to loss of sodium and potassium), dehydration and death
– Treatment: Radid replacement of fluid and salt. Antibiotics if very early, support with fluids and salts. The antibiotics are only effective in the very early stages.
– Prevention: (more on a personal level) Vaccination for the specific strain. Boiling any water you drink or treat chemically. Don’t have food washed in local water. Peel foods.
– Control: (Population basis government) Keep water and sewage separate from each other. Water treatment. Supply uncontaminated water (fresh water). Sanitation and sewage systems. Public education about home remedies and boiling water and food/water handling.
3.D Process information from secondary sources to discuss problems relating to antibiotic resistance
Antibiotic resistance: With the widespread use of antibiotics, a problem that threatens the successful treatment of these diseases has developed. Bacteria, during the normal process of natural selection, have evolved strains that are resistant to many, if not all, of the antibiotics that are used to treat infectious disease in the world today.
Natural selection and resistance: Darwin’s theory states that in any population there is variation. In a particular environment, the organisms that have a variation that is best suited to that environment survive and reproduce. This produces a population in which most organisms are adapted to survival in that particular environment.
When antibiotics are administered to treat a bacterial infection, some of the bacteria present may possess a natural resistance to the particular antibiotic and so they survive. They then reproduce and can quickly build up a population that is resistant to the antibiotic. In conjunction with this, the bacteria are also capable of passing this resistance on to other bacteria they come into contact with, further building up the population of resistant bacteria. (bacteria can sway DNA between species)
It is helped by the fact that bacteria multiply and mutate rapidly increasing the chance of resistance genes occurring naturally. Natural selection then favours the resistant bacteria. Adding to this problem is the fact that most resistant genes occur on plasmids (circular DNA) which bacteria are able to pass to other bacteria, even between species.
Important: Must not write that bacteria develop resistance. It is a pre-existing trait that may be passed on.
Examples: Particular concern include MRSA- Methicillin resistant staph awreis, Vancomycin resistant enterococcus, TB resistance (Teburculosis)
Human practises contributing to antibiotic resistance: Over use of antibiotics eg for viral infections such as a cold/flu. Not finishing antibiotic courses selects the most resistant bacteria leaving them to multiply. Putting antibiotics in animal feed to increase population, selects the resistant ones, kills the non-resistant one in the animal stomaches. Massive use of antibiotics in hospitals. Use of anti-bacterial ingredients in cleaning products, encourages resistant strains as they are not strong enough to fully kill the bacteria.
Problems with anti-biotic resistance: some types of antibiotics are not longer effective. Some diseases that used to be curable eg TB now have resistant strains. New anti-biotics are being developed but they are more expensive and more toxic. In some countries its to expensive and the diseases become untreatable. There are some ‘super bugs’ that have evolved and are resistant to all treatment.
Ways to deal with it in the future: Only use them for bacterial infections, strict hygiene in hospitals, public should be educated about taking the whole packet of anti-biotics. Penalties should occur for illegal use.
4 Often we recognise an infection by the symptoms it causes. The immune response is not so obvious, until we recover.
4.1 Identify defence barriers to prevent entry of pathogens in humans:
First line of defence. Non-specific- react to anything foreign.
Skin: tough outer barrier. The skin is dry which limits growth of pathogens. Microorganisms can not penetrate the ‘keratin’ on the outer layers of the skin, unless its broken. There are normal harmless bacteria on the skin which keep invading pathogens from multiplying. Sebaceous glands in the skin secrete sebum. Lipids in the sebum are broken down by the skin’s harmless bacteria to produce acids which inhibit the growth of some bacteria and fungi. If the skin is broken, the blood-clotting mechanism very quickly forms a seal across the wound to prevent the entry of pathogens.
Mucous membranes: Line the digestive, respiratory, reproductive and urinary tracts with a thick, slimy mucus. This membrane must allow for the exchange of substances when needed and also protect against invasion. This protection is aided by the presence of an antibody called IgA in mucus which reacts with potential pathogens, preventing them from invading the surface.
Cilia: Minute hairs that project from the cells lining the respiratory surfaces of the nose, trachea and bronchial tubes. As the cilia beat they sweep mucous along so that any particles breathed in and trapped in the mucus are transported to the nose opening or to the pharynx where they are coughed out or swallowed. Sneezing and coughing expel pathogens. Eyelashes and eyelids hel to stop pathogens and dust entering eyes.
Chemical barriers: Conditions make the surface inhospitable for the potential pathogens. Eg alkaline environment in the small intestine.
Other body secretions: Saliva, tears, sweat and naval secretions contain lysozymes which break down the cell walls of some types of bacteria. There are populations of harmless microorganisms in the vagina. They act on cells shed from the walls of the vagina to create acid conditions which inhibit the growth of some bacteria and fungi. Urine is a sterile, acid fluid. It flushes the ureters, bladder and urethra and helps prevent the growth of microorganisms. Peristalsis (intestine contracts and expands to move food) and vomiting or diarrhoea move food and pathogens out through anus or mouth.
4.2 Identify antigens as molecules that trigger the immune response.
Antigen: Antibody generating generates antibodies
Any molecule that triggers an immune response. Antigen is recognised as foreign or ‘non-self’ by the body. Antigen is not just pathogens, but also foreign cells, parts of cells, toxins and even snake venom.
4.3 Explain why organ transplants should trigger an immune response.
When the transplant is from one person to another the recipient’s body usually reacts to the proteins in the transplanted tissue or organ as foreign and so produces antibodies against them. This is referred to as tissue rejection. It is important that the tissues of the donor be typed and matched as closely as possible to those of the recipient. Close compatibility of the tissues lessens the risk of rejection.
Tissue rejection is brought about by the T lymphocytes. Rejection can be reduced by immunosuppressive drugs and using x-rays. The problem is thought that these drugs kill most lymphocytes thus not only tissue rejection is suppressed but also other immune responses. Therefore recipients of transplants have reduced resistance to other infections which may be lethal.
Note: implantations/ artificial device eg pacemakers, are made from plastics and metals thus do not stimulate antibody production.
4.4 Identify defence adaptations, including:
Second line of defence. Non-specific.
-Inflammation response: blood vessels dilate to bring blood and fluid to the site of the infection or damage causing the area to become hot, red, swollen and painful. Bringing more blood to the surface increases the number of white blood cells and helps the destroy the pathogen. Dead cells and toxins can be removed quickly and repair of the tissues can begin. The inflammation responses are mediated by chemicals such as histamine and prostaglandins released from the damaged tissues. These chemicals increase the permeability of the capillary walls so they become more ‘leaky’ allowing phagocytes to enter the area and remove cells debris.
-Lymph system: Lymphocytes are white blood cells that become active in chronic inflammation. The lymphatic system in the body contains lymph vessels that form a drainage system. If there is an infection in the tissues the foreign particles, along with dead cells and other debris get moves along with the tissue fluid into the lymph vessels. Along the vessels are lymph nodes. Here the waste particles are filtered and foreign particles are destroyed by macrophages. This is why swollen lymph nodes are good indicators of infection.
-Phagocytosis: Phagocytes are the white blood cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells. The phagocytes actively move from the blood to the tissues where they ingest and destroy any foreign material eg pathogens and this is called phagocytosis. In acute inflammation (lasting hours or days) the main phagocytes are called neutrophils, in chronic inflammation (weeks or months) the main phagocytes are called macrophages.
Phagocytes attack foreign substances by engulfing and destroying them. Phagocytosis occurs when an organism succeeds in passing the first line of defence and enters deeper tissues. (Phagocytes are non specific)
-Cell death to seal off pathogen: When the body is unable to neutralise an antigen, a particular type of chronic inflammation involving both macrophages and lymphocytes may occur. This reaction forms a cluster of cells called a granuloma in which a central core of dead tissue is surrounded by layers of machrophages, then lymphocytes, then fibroblasts (a cell from which connective tissue develops) which produce a tough outer wall. Granulomas are produced in tuberculosis and leprosy. In TB they form around site of infection in the lungs, preventing the enclosed bacteria from causing further infection.
4.A Gather, process and present information from secondary sources to show how a named disease results from an imbalance of microflora in humans
The human body contains a variety of microbes. These microbes are known collectively as the microflora of the body. They inhibit the growth of pathogens. If conditions in the body change there is an imbalance of microflora which means pathogens can not be controlled and this leads to an increase in their numbers and development of disease.
Name of disease, both scientific and common: Candidiasis or Thrush
Causative pathogen: Fungus, Candida albicans
Symptoms: Mouth and pharynx: oral candidiasis, white patches develop in the mouth and throat. May occur as a result of infection during birth. Can also occur with some forms of cancer. Vagina: vulvovaginal candidiasis, itchiness, irritation and discharge.
What normally controls C.albicans? The number of C.albicans is usually kept in balance by competition from other micro-organisms for food and resources. Normal microflora controls it.
When would C.albicans cause thrush? Vagina: can result from altered pH in the vagina which causes C.albicans to increase in number because the lactobacilli (normally present) no longer keep the fungus in balance. In the natural balance is disturbed the numbers of C.albicans can increase, gain dominance and various pathological conditions can occur causing thrush.
What health factors could predispose a person to developing thrush?
• Diabetes mellitus
• Old age
• General weakness eg when cancer is present
• Immune suppression (drugs that suppress immune system eg antirejection, upset the balance of normal microflora and the immune system is effected)
Describe how taking antibiotics could result in thrush.
Normal microflora include fungi and bacteria. Antibiotics kill bacteria leaving the fungi. Taking antibiotics to treat bacterial infection can upset the natural balance of microflora thus can cause thrush. Antibiotics can not only kill pathogenic bacteria in the body but also reduce bacteria in microflora. This allows C.albicans to multiply uncontrollable therefore a disease such as thrush can establish
Thrush conclusion: Candidiasis is caused by a fungi Candica albicans. It is part of the normal micro-flora and the mucous membranes of the human body and is usually kept in check by competition from other normal microbes including bacteria. If the natural balance is upset the number of C-albicans can increase causing disease (opportunistic infection)
Predisposing factors include those that lower immunity in the host such as HIV, radiation or chemo therapy, diabetes, chronic illness, pregnancy and old age, drugs such as steroids (antirejection)
Antibiotics kill bacteria which compete with C.albicans therefore predisposing (making it more likely to get thrush) towards thrush.
5 MacFarlane Burnet’s work in the middle of the twentieth century contributed to a better understanding of the immune response and the effectiveness of immunisation programs
5.1 Identify components of the immune response: as Antigens, T cells and B cells.
Antibodies: are proteins produced in response to the presence of an antigen in the body. When the appropriate B cells are activated they form plasma cells that produce antibodies, the antigen binding sites of which match the shape of the antigen they are specific for. The antibodies then seek out the antigen and bind to a part of it and causes the deactivation of the antigen.
T cells: cell mediated immunity, carried out by specialised cells circulating around the body.
B cells: antibody mediated immunity, production of antibodies that circulate around the body in the blood and lymph.
5.2 Describe and explain the immune response in the human body in terms of:
–Interaction between B and T lymphocytes
• When a macrophage encounters a foreign particle with an antigen it undergoes phagocytosis
• While destroying this foreign material the antigen that was present on its surface is moved to the surface of the macrophage which then transports it to the lymph nodes
• The antigen presenting macrophage is then presented to the helper T cell that has a T cell receptor that corresponds to that particular antigen- the helper T cell is activated
• The helper T cell can also be activated by B cells. When a B cell encounters the antigen that corresponds to its surface antibodies it binds these antigens to these antibodies. It then processes the antigen, attaches it to its surface molecules and presents this to the helper T cells that have the matching T cell receptors
• The helper T cells produce a cytokine chemical to activate the production of clones of the B cells that are specific to that antigen. This also activates the production of clones of the cytoxic T cells that have that particular antigen receptor on their surface
• When the immune response has successfully defeated the infection, suppressor T cells are responsible for suppressing the activity of the B cells and cytotoxic T cells
-The mechanisms that allow interaction between B and T lymphocytes
• To help B and T cells interact successfully there is a system that allows the cells to identify that they both belong to the body and prevents them from attacking each other.
• The cells have proteins on their surfaces called MHC molecules. This allows the recognition of cells from the body and allows identification of cells that are foreign. (foreign cells have different MHC molecules on their surface) (MHC molecules are chemicals on the outside of membranes that hold antigens)
• There are 2 types of MHC molecules: MHCI- present on all cells that have a nucleus and are involved in the recognition of antigens by T cells. The infected cell holds the MHCI molecule on the surface so that the cytotoxic T cell can identify it and destroy it. Display antigen made within the cell, such as self antigen. MHCII- found on macrophages and B lymphocytes, displays phagocytosed (eaten) antigen.
-The range of T lymphocyte types and the difference in their roles
5.3 Outline the way in which vaccinations prevent infection
Vaccination involves giving a killed or weakened form of a pathogen by injection or orally. This stimulates a 3rd line immune response resulting in the formation of antibodies and memory cells, while producing no symptoms. Next time the body is exposed to the same pathogen there is a rapid and strong immune response to overcome it. Booster injections are used to increase antibody and memory cell levels as they drop over time.
Vaccines do not result in the symptoms of the disease. They act as antigens and bring out the primary immune response and this produces immunity against a particular pathogen. Should the same pathogen re-enter the body, the secondary immune response occurs.
There are some people who do not want to immunise their children as they are scared of the slight chance that they may have a reaction. These people rely on others to do the right thing. They may be fine as most people have had the vaccine but if there are a cluster of children without the vaccine and there is one that gets it there could be an outbreak.
5.4 Outline the reasons for the suppression of the immune response in organ transplant patients.
The donated organ has, on its surface, marker molecules that are different from the marker molecules on the cells in the recipients body. Therefore the markers act as antigens and are identified as foreign thus the immune response is initiated. The cytotoxic T cells are activated and move to the transplanted organ to attack and destroy the cells. This causes the rejection of the transplanted organ.
Doctors try to find close matches of tissue types when possible. Drugs can also be used to suppress the immune system as this reduces the risk of rejection. The drugs reduce the activity of the T cells this means that the whole immune system is not suppressed and can still defend the body against other disease-causing organisms. However it will still not be as effective and the recipient is at a much greater risk of suffering from more infections.
6. Epidemiological studies involve the collection and careful statistical analysis of large quantities of data. Such studies assist the casual identification of non-infectious diseases.
6.1 Identify and describe the main features of epidemiology using lung cancer as an example.
Epidemiology is the study of patterns of health and the distribution and frequency of disease, illness and injury in a society.
• Collecting large quantities of data about a disease and analysing it statistically Eg lung cancer; melanoma-who gets it, when, where, lifestyles
• Analysing and interpreting the data gathered to look for trends
• Looking for the cause and effect of a disease especially non-infectious by studying patterns and trends in the statistics (analysis)
• Groups that must include a diverse range of types of people, age, sex, race etc. And each group must have the same composition with regard to those characteristics
• Avoiding bias
• Possible cause of disease (usually non-infectious)
• Risk factors
• Transmission (for infectious disease)
Use by health departments and governments to:
• Determine best methods for controlling and preventing
• Formulate public education campaigns
• Formulate preventative medicine measures
• Support vaccination programs for infectious diseases
When studying lung cancer as an epidemiology study there had to be large quantities of data collected; large sample sizes; over long periods; different populations from different countries; random; repeated; data analysed and interpreted to look for trends.
The trends found were:
• Smokers have a 10 times greater chance than non-smokers of dying from lung cancer
• The more cigarettes smoked each day, the greater the incidence of lung cancer
• The longer a person smokes the greater the chance of developing lung cancer
• Greater risk of developing lung cancer due to passive smoking
• As it became more socially acceptable, the number of females smoking increased and the incidence of lung cancer in women increased
• Smoking accounts for 85% of cases of lung cancer in men and 75% in women
6.2 Identify causes of non-infectious disease using an example from each of the following categories:
-Inherited diseases: Genetically transmitted and are caused by errors in genetic information. Errors may include: change in chromosome number eg down syndrome or a defect in a single gene caused by mutation eg Cystic Fibrosis. Other examples include haemophilia, colour blindness, dwarfism and albinism.
Caused by: mutation of a gene on the 7th chromosome. It is autosomal (not sex linked) meaning it does not occur on a sex chromosome.
Symptoms: Excess production of mucous especially in the lungs. Results in shortness of breath, effected digestion resulting in weight loss. Mucous blocks lungs leading to chromic respiratory infections.
Treatment: physiotherapy to help drain excess mucous. Diet low in dairy products, enzyme supplements to help digestion and gene therapy (inhale CF gene to give temporary relief)
-Nutritional deficiencies: Can be caused by diets lacking the proper balance and amount of nutrients. Can also be caused by psychological conditions that lead to inappropriate diets.
Iron deficiency: Anaemia
Due to: lack of iron or folic acid, less oxygen being carried around in the body by iron in red blood cells.
Symptoms: patients feel continually tired and lack energy. They also appear pale.
Treatment: iron tablets or a diet rich in iron eg red meat
-Environmental diseases: there are many different types including lifestyle diseases caused by substance abuse eg smoking related diseases and cardiovascular diseases, diseases caused by physical factors in the environment eg skin cancer- excessive exposure to sunlight and diseases caused by exposure to chemicals in the environment eg lead poisoning from high levels of pollution in the atmosphere
Caused by: mutations in lung cells due to chemicals in cigarette smoke changing the DNA. This causes mutation of abnormal cells that reproduce and are useless. Cancer occurs when cell division by mitosis goes wrong.
Symptoms and effects: tumours grow which cause pressure and pain on surrounding tissue. This squashes the trachea and blood vessels etc so lungs stop working which causes coughing, chest pain and shortness of breath. The cancer may be malignant which means it can break off and spread
Treatment: cancer can be detected by x-rays because the lump is not as soft as lungs. Radiation therapy (gamma ray penetrating- cobalt60). Chemotherapy- powerful drugs are taken intravenously which kill the cancer cells. Surgery can remove cancer. Management: stop it spreading in the community, public health ads eg anti-smoking ads
6.A Gather, process and analyse information to identify the cause and effect relationship of smoking and lung cancer
A cause and effect relationship is a relationship in which an action that is taken will then initiate or influence a second action to occur. For lung cancer studies have shown that there is a clear link between smoking and the increases incidence of lung cancer and a clear link between cigarette smoking and reduced life expectancy.
6.B Identify data sources, plan and perform a first hand investigation or gather information from secondary sources to analyse and present information about the occurrence, symptoms, cause, treatment/management of a named non-infectious disease.
Occurrence: Most common nutritional deficiency worldwide. Most common in infants, young children, the elderly and women of child bearing age. Low iron stores have been reported in up to 1/3 of young children aged 1-3 years in Australia.
Symptoms: lethargy (tiredness and lack of energy), poor development, blood levels decrease. Has been linked with problems such as mental delay and reduced immune function. Some have no symptoms.
Cause: Some risk factors in children include: prematurity, low birth weight, excusive breastfeeding beyond 6 months, introduction of cow’s milk as the main drink before 12 months and high intake of cow’s milk, delayed introduction of solids, low (or no) meat intake and general poor diet in the second year. Children and teenagers are growing thus need an increase in iron and this may not be fulfilled if they don’t have a balanced diet.
Treatment/ management: Dietary change to obtain more iron, may include iron supplements. Eat more meat, poultry and fish, include vitamin C as it helps to absorb more iron.
7. Increased understanding has led to the development o a wide range of strategies to prevent and control disease
7.1 Discuss the role of quarantine in preventing the spread of disease and plants and animals into Australia or across regions of Australia
Australian Quarantine and Inspection Service (AQIS)
• Part of the Australian government department of agriculture, fisheries and forestry (DAFF)
• Manages quarantine controls at our border to minimise the risk of exotic pests and disease entering the country
• Provides import and export inspection and certification to help retain Australia’s highly favourable animal, plant and human health status and wide access to overseas markets
• AQIS helps to keep out biological threats such as foot and mouth disease
Role of quarantine
• Quarantine has prevented the entry of food and mouth disease
• Within Australia quarantine has prevented the spread of certain diseases between states. Movement of plant material such as fruit and plants stock has been restricted by laws to prevent diseases spreading
• Quarantine regulations now apply to importations and customs at airports and shipping terminals
• Isolation of disease victims are isolated to prevent the spread of disease (eg the plague in 1900)
• Quarantine is what prevents the spread of disease by making sure they don’t get into areas that are free of that disease.
• Quarantine seeks to prevent the entry of harmful diseases into Australia and to stop the spread of diseases within Australia.
7.2 Explain how one of the following strategies has controlled and/or prevented disease: public health programs, pesticides or genetic engineering to produce disease-resistant plants and animals
Public Health Programs
• Aim to reduce health hazards and prevent disease
• Includes advertising: media, posters, pamphlets. Special programs: immunisation, quarantine, facilities eg clean water and sanitation
• They are also responsible for advertising campaigns that target cancer and AIDS. Examples of successful health campaigns are the Slip! Slop! Slap! skin cancer advertisements, the advertisements that show various diseases that can be caused by smoking and the Grim Reaper series for education about AIDS
• These programs help control and prevent diseases by directly linking to the cause of the disease.
• Other examples include: QUIT (1997-2005) Aims to make smokers aware of the effects of smoking to reduce numbers of smokers and lung cancer. How do you measure up (2006-2010( to make people aware of how being overweight can effect your health and others around you. To encourage them to do something about it. Chromic diseases eg cancer, heart disease, type 2 diabetes.
7.A Perform and investigation to examine plant shoots and leaves and gather first hand information of evidence of pathogens and insect pests
• We examined different leaves from plants with microscopes and by simply observing.
• We used evidence that we saw to determine what kind of organism caused the disease
Examples/ our observations
(important when describing that you use the word ‘abnormal’ because some plants may have normal brown spots etc)
• Evidence: there are holes in the leaf, there are faeces on the leaf. Cause: cabbage moth, caterpillar
• Evidence: black dots on the leaf (dead cells from virus). Cause: Orchid fleck virus (can spread from leaf to leaf)
• Evidence: leaf is crinkled up and deformed. Cause: citrus leaf miner, tiny caterpillar (insect pest) Moth lays eggs on the leaf and the tiny moths burrow inside and eat it away, destroy from the inside which causes the crinkling and folding
• Evidence: abnormal dark brown marks/ patches on the leaf. Cause: fungus (the patches is fungus)
• Evidence: Bugs on the plant, plant looks dehydrated and unhealthy. Cause: aphids (insect pest), they suck out the sap of the plant which dehydrates it
• When you cut the plants you must clean the instrument before you cut another plant to prevent disease spreading
• Dispose of the plants in the bin inside a plastic bag so the diseases don’t spread onto other plants
• Wear gloves
- Take care with sharp instruments
7.B Process and analyse information from secondary sources to evaluate the effectiveness of quarantine in preventing the spread of plant and animals diseases into Australia or across regions of Australia
Examples of effectiveness of quarantine
7.C Gather and process information and use available evidence to discuss the changing methods of dealing with plant and animals diseases, including the shift of emphasis from treatment and control to management or prevention of disease
Treatment is the management of someone or something, care provided to improve a situation. While prevention is the act of preventing, to stop someone or something from doing something or being in a certain state, to keep from happening or arising. The methods of dealing with plant and animals diseases have changed from treatment measures towards preventative measures as scientists and medical professionals have determined that its best to target and get rid of the disease before it has a significant impact. This can be seen through examples of change in management of cholera and melanoma as well as plant pathogens such as insects and fungi.
Past measures taken against cholera included treatment such as fluids and antibiotics for those who were effected. They rehydrated patients using a saline drip and prescribed antibiotics in the early stages of the disease. Over time these measures have changed. Today there are public health programs such as educating on personal hygiene and boiling untreated water. There are also public works such as water monitoring and treatment, sewerage management and treatment and assistance to 3rd world countries at risk. All these programs help to prevent an outbreak.
Management of melanoma has also changed. Past treatment included removing the melanoma through surgery, sometimes followed by radiotherapy and chemotherapy is the cancer was widespread. People still continued to smoke and just dealt with the cancer if it occurred. Today management has changed. There are epidemiology studies to examine the cause of melanomas and relate to human behaviour so that they know how to prevent it. There is also more technology such as mole machines that can monitor any small changes to a pre-existing mole, allowing for earlier detection hopefully before the cancer spread. The most important preventative measure in regards to melanoma is public health awareness campaigns. These campaigns such as “Slip, Slop, Slap and Wrap” and “Me No Fry” are designed to discourage risky behaviour and to prevent people from getting a melanoma in the first place, thus reducing the cases of the disease.
Management has also changed for plant pathogens such as insects and fungi. Plants used to be sprayed with toxic insecticides such as DDT and dieldrin, which killed any pathogens harming the plants at the time. These chemicals can be harmful to humans and the food chain and can also kill useful insects such as bees and insect predators eg ladybird larvae (which feed on aphids). Today plants can be genetically modified and engineered to have certain genes that are beneficial. Examples include BT cotton and Canola that have a gene from a soil bacteria which kills leaf eating insects. This is a preventative measure as the crops will now be able to fight off the insects themselves thus wont be negatively effected. Old insecticides have been replaced with less toxic sprays which are better for the environment and humans.
Other common new preventative ways of management of disease include quarantine and vaccine. Quarantine “seeks to prevent the entry of harmful diseases into Australia and to stop the spread of diseases within Australia.” There are quarantine offices at airports who inspect luggage from travelers to make sure that no harmful diseases are entering. There are also quarantine laws between states that make sure that diseases and pests such as fruit fly don’t spread between states. Quarantine stops these diseases from even entering the country or state therefore is preventative measure. Vaccination helps people to become slightly immune to certain diseases. This allows the body to more easily fight off the disease. Therefore vaccination programs prevent the spread of diseases as it lowers the chance of people contracting the disease.