Download Search for Better Health #2

The Search for Better Health
What is a healthy organism?
Difficulties of defining ‘health’ and ‘disease’:
 Disease is any condition that adversely affects the function of any part of a
living thing. Many diseases are best understood as a disturbance in
homeostasis.
 Health refers to the overall well-being of an organism, not just the absence of
disease.
 Different organisms will differ in health and susceptibility in disease. It is
possible for a person to be healthy and have a disease at the same time,
making it difficult to define both health and disease.
How the function of genes, mitosis, cell differentiation and specialisation assist in
the maintenance of health:
 The degree to which an organism is healthy depends on whether or not its
cells are functioning properly and how well the body can repair a malfunction
or imbalance. Gene expression is essential for the maintenance of health.
 Genes control the process of protein metabolism. The growth of tissues and
the healing of tissues are dependent on protein metabolism.
 Mitosis is the cell division that will allow normal growth and repair. If the
processes controlling mitosis go wrong, cancer may occur.
 Cell differentiation is the process undergone by the cells after mitosis. Each
cell differentiates to become a specialised cell. Undifferentiated cells form
tumours.
 Cell specialisation allows cells to develop the structure to best perform
specific functions. Many types of cells have specialised roles in maintaining
the health of an organism.
The maintenance and repair of body tissues in relation to gene expression:
 Gene expression refers to the transfer of information from a gene to produce
a new protein or RNA. It can occur throughout the life of an organism,
specifically for repair and maintenance of tissues.
 Constitutive genes are expressed continually to maintain normal body
functions, e.g. genes that code enzymes in digestion are expressed frequently
to produce sufficient amounts of saliva during digestion. Other genes
(facultative genes) are only expressed when needed.
 There is still much to be understood about the processes of repair of tissues
and the switching on of genes to initiate this.
 One group of scientists identified a REG (regenerating) family of proteins in
the human digestive system lining. These proteins are not normally
expressed by appear in large amounts in certain bowel diseases. Their
expression is tightly linked with tissue repair and regeneration.
 When there are sufficient cellular materials and organelles, mitosis allows
cells to divide. The cells may then continue gene expressing to develop
specialised structures so that they are differentiated for specific purposes.
Over 3000 years ago, the Chinese and Hebrews were advocating cleanliness in
food, water and personal hygiene
Infectious and non-infectious diseases:
 An infection is the presence of a disease-causing organism in or on the body
of a host. Infectious diseases can be spread from one organism to another by
direct or indirect transmission. Examples include influenza, chicken pox and
measles.
 Non-infectious diseases cannot be spread from one organism to another.
They can be caused by genetic factors, environmental factors, diet or
physiological malfunction. Examples include Down syndrome, haemophilia
and skin cancer.
Why control of disease is assisted by cleanliness in food, water and personal
hygiene practices:
 There are huge numbers of microscopic disease causing organisms, and
minimizing the number of such organisms in our food and water reduces the
risk of infection.
- Control of disease caused by organisms includes:
 Ways of preventing contamination of food and water through proper
sanitation, proper food handling, personal hygiene and water treatment
processes
 Ways to prevent decomposition and spoilage of food
 Ways to prevent transmission of the disease and infection by using
disinfectants, sterilisation and antiseptics. Crowded conditions, poor
sanitation and untreated sewage increase the spread of disease.
Identifying microbes in food and water:
 Aim: to culture microbes growing on bread or a piece of fruit and to identify
them
 Method: collect a piece of fruit or old bread that has developed a furry
growth or mould. Sterilise an inoculating loop and use it to collect spores and
spread them in a regular pattern over the agar. Close the lid on the agar
plate, then incubate and observe the growth of colonies. Generally, shiny,
smooth colonies are bacterial and furry colonies that develop spores or spots
are fungal.
 Conclusion: generally, bacteria have shiny colonies and fungi have furry
growths of mycelium and spore-producing structures on agar.
The conditions under which an organism is described as a pathogen:
 A pathogen is any organism that can produce a disease.
 If a pathogen is to cause a disease it must:
o Have enough virulence (the number of the particular pathogen
needed to cause the disease)
o Live in or on the host without being destroyed by the body’s immune
defence
o Escape from one host to another, and survive the transmission from
one host to another.
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Pathogens cause disease symptoms in a number of ways:
o The large number of pathogens present are too many for the host
tissue to function normally
o The pathogens actually destroy cells or tissues
o Bacteria produce poisons called toxins
o The pathogen may not directly harm the host, but an excessive
immune response by the host may damage tissue
The treatment of drinking water:
 Contamination of drinking water is a common way for pathogens to enter the
body. Heat, water and detergents can be used to achieve cleanliness, kill or
remove pathogens.
 Boiling, radiation, chlorine, microfiltration and distillation all destroy
microorganisms by breaking down the cell wall.
 Proper treatment of water works to remove impurities and microbes that can
cause disease. This happens in three steps:
o Coagulation: addition of chemicals to clump all organic matter
together as flock. As it settles, it is then removed.
o Filtration: water flows through composed of virus and protozoan
removal methods. This includes sand beds and more recently
membrane filtration.
o Disinfection: use of chemicals to disinfect water.
Reducing the risk of infection from pathogens:
 The removal of fine suspended particles by coagulation and filtration is
important as these small particles attract and hold bacteria and viruses. This
alone removes approximately 99% of bacteria and viruses.
 Oxidising substances such as chlorine and ozone kill microorganisms.
Ultraviolet light at the correct levels also kills bacteria and viruses, though
there is some doubt about efficient protozoan removal.
 In NSW, water is filtered, chlorine is added to kill bacteria and samples are
tested for the presence of coliform bacteria, giardia and cryptosporidium.
The work of Pasteur and Koch and other scientists stimulated the search for
microbes as causes of diseases
The contribution of Pasteur and Koch to our understanding of infectious diseases:
 Pasteur discovered that microbes such as bacteria can cause disease. He
disproved the theory of spontaneous generation through his famous swanneck flask experiment, as well as showing that micro-organisms came from
pre-existing microorganisms.
 Koch showed that bacteria were the cause of a disease called anthrax in
horses, cows, sheep and humans. He also demonstrated that bacteria were
the cause of tuberculosis in humans.
 During Koch’s work on diseases, he designed rules of procedure for showing
that a particular microorganism is the cause of a particular disease. These
rules of procedure are called Koch’s postulates. Koch’s postulates can be
used to identify the causative organism of an infectious disease.
Koch’s postulates are:
 Step 1 – all infected hosts must contain the suspect organism
 Step 2 – a pure culture of the suspect organism must be obtained
 Step 3 – a healthy organism infected with the pure culture must have the
same symptoms as the original host
 Step 4 – the suspect organism must be isolated from the second host, grown
in pure culture and prove to be identical to the first culture
Modelling Pasteur’s experiment:
 Aim: to model Pasteur’s experiment in order to demonstrate that microbes
cause decay
 Method: Prepare a nutrient broth and place 150mL into two flasks, one with
a straight neck, the other with a swan-neck. Leave the flasks for 5 days. Look
for cloudiness, scum, bubbles and mold colonies.
 Results: The broth in the straight neck flask went cloudy, developed scum,
bubbled and produced unpleasant odours while the broth in the swan-neck
flask remained unchanged. Both flasks were open to the air, however the sshape in the swan-neck was able to trap microorganisms before reaching the
broth.
 Conclusion: microbes could not grow spontaneously. Fermentation relies on
the entry of microbes.
The cause and prevention of malaria:
 Malaria is a disease transmitted by an insect vector – female mosquitos.
Symptoms include sweats, fever, delirium, headaches and chills. There are
different strands of malaria. Ronald Ross’ work on malaria identified insects
as vectors of disease. A vector is an organism, usually an anthropod, which
acts as a carrier of a pathogenic organism.
 It was originally believed that living near swampy areas caused malaria, but in
1880, French army doctor Laveran discovered the protozoan Plasmodium
that caused the disease. He searched for a form of protozoan that could
show its transmission from human to human without success. He eventually
suggested that mosquitos might be the vectors.
 In 1987, Ross found cysts in the stomach walls of the mosquito Anopheles
and identified the cysts as the malaria-causing parasite. Ross proved that
mosquitos transmit malaria and began investigations into transmission and
control of the disease.
Life cycle of malaria
 Anopheles mosquitos act as a vector, carrying the pathogen to the host.
Malaria has a two stage life cycle – one part mosquito, one part human.
During the blood meal, the Plasmodium is transferred from the mosquito
salivary glands and into the blood system of the host.
 Once inside the human blood stream, the parasite travels to the liver and
reproduces asexually in the liver cells. These cells burst and the parasite float
freely in the blood, feeding on the haemoglobin. The mosquito picks up the
parasite when it bites an infected human and sexual forms develop in the
mosquito’s gut.
Control and prevention of malaria:
 Reducing the population of the vector – spraying with pesticides, identifying
and removing breeding sites and introducing surface minnows, a fish that
feeds on mosquito larvae, therefore decreasing the population
 Reducing the contact between the vector and the host – education programs
informing people of the risk of contracting malaria and ways to prevent
mosquito bites, such as insect repellent and mosquito netting
 Drugs – people are advised to take chloroquine if entering a malaria infested
area. Chloroquine interferes with the development of the parasite.
 Research is progressing into releasing genetically modified, sterile
mosquitoes that will compete with natural mosquitoes for mates, and so
reducing the population of mosquitoes.
 Another program has produced mosquitoes that have been modified to
prevent the development of Plasmodium.
Types of pathogens that cause infectious diseases in plants and animals:
Prion
Virus
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Bacteria
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Protozoan
Fungi
Macro-parasites
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Defective for of a protein molecule
Doesn’t contain DNA or RNA
Mostly attacks brain or nerve cells
Non-cellular
Contains DNA, RNA and protein
coat
Requires a living host cell to
replicate
Procaryotic cell
Divides quickly and/or produces
toxins
Very simple cell with no internal
membrane
Eucaryotic cell – single-celled
organism with internal membranes
May have a complex life cycle
Eucaryotic cell w/ cell wall
Spreads via spores or rapid division
Heterotrophic organisms
Some infect external skin and nails,
while others enter the host’s body
Also called parasites
Eucaryotic cells – multicellular
organism
Visible to the naked eye
Mostly anthropods or worms
Prions:
 Newly discovered infectious agents that consist only of protein (no nucleic
acid). The prion hypothesis states that certain diseases are caused not by
known pathogens but by a protein that has adopted an abnormal diseaseproducing form.
 Prion diseases are both infectious and hereditary. Examples include scrapie in
sheep, mad cow disease and CJD (Creutzfeld-Jacob Disease)
Viruses:
 Consist of a nucleic acid (DNA or RNA) surrounded by a protein coat.
 Viruses invade cells and insert their genetic code into the host cell’s genetic
code. Examples include Hepatitis B (viral liver infection), Herpes simplex 1
and 2 (cold sores and genital herpes) and Paramyxovirus (measles and
mumps)
Bacteria:
 Tiny procaryotic cells that can caused disease by secreting toxins, invading
cells and forming bacterial colonies that disrupt normal cell function.
Examples include enterobacteria (salmonella diseases and gastro) and
bacterial leaf spot (causes rotting of leaves and stems in snapdragons).
Protozoans:
 One celled organisms, larger than bacteria, with the DNA organized in a
nucleus (eucaryotic cells). Examples include giardia: a flagellate protozoan
(diarrhoea) and plasmodium: a sporozoan protozoan (malaria)
Fungi:
 Simple organisms, similar to plants but without chlorophyll. Examples are
yeast and mould. Fungal diseases include candida (thrush) and tinea
(ringworm and athlete’s foot).
Macro-parasites:
 Multicellular parasites such as roundworms, flatworms (tapeworms) and
flukes (liver fluke) and anthropods such as ticks, mites, lice and fleas.
Infectious diseases (malaria):
Cause
Transmission
Host response
Major symptoms
Treatment
Prevention
Control
Protozoan, plasmodium
Anopheles mosquito (female) salivary
glands  human  blood cells  liver
cells  human blood cells  anopheles
mosquito
When in the blood cells, the host
produces antibodies against the
Plasmodium
Chills, fever, sweating, delirium,
headaches
Anti-malarial drugs such as quinine
chloroquine
Insect repellent, mosquito nets
Draining swamps, insecticides
How antibiotics assist the management of infectious diseases:
 Antibiotics are compounds that kill or inhibit bacterial pathogens. They serve
mainly as a treatment but in some extreme conditions, such as burns victims,
they may be used to prevent infection.
 When taking antibiotics, the full course should be taken to avoid the more
resistant members of a population surviving and developing more resistant
strains.
The problem of antibiotic resistance:
 Resistance to antibiotics is an increasing concern. The overuse of antibiotics
has led to the selection of more virulent bacteria that are resistant to
antibiotics.
 People do not take antibiotics correctly by not taking the full dose, or taking
them incorrectly. The problem arising from that is bacteria then becomes
increasingly harder to treat, resulting in a more serious infection.
 When antibiotics were first introduced, they had a dramatic effect on the
pathogens that cause disease. Over time, it became apparent that the effects
of the antibiotics were beginning to become less potent. Overuse of
antibiotics has resulted in "superbugs". Unless new antibiotics are produced
to fight bacteria, common infection will once again be responsible for many
deaths.
Defence against disease
 Our bodies have three types of defence against pathogens.
 The first consists of several barriers that prevent the entry of pathogens.
 The second is the action of white blood cells in destroying foreign particles
(phagocytosis).
 The third is carried out by the immune system, which plays a complex role in
targeting and destroying pathogens as well as helping to make our bodies
immune to them.
Defence barriers to prevent entry of pathogens in humans:
- Skin:
 The skin is a mechanical barrier. Unbroken skin protects other tissues, and
collects and holds pathogens.
- Mucous membranes:
 Cells that line the respiratory tract and openings of the urinary and
reproductive systems that secrete a protective layer of mucous. Mucous is a
sticky substance and hence traps pathogens from entering the body.
- Cilia:
 Hair like projections from cells lining the air passages. They move with a
wave-like motion to push pathogens from the lungs up to the throat.
- Chemical barriers:
 Chemicals like acid in the stomach, alkali in the small intestine and lysozome
in tears destroy pathogens before entering the body.
- Other body secretions:
 Secretions including those from sweat glands and hair follicles. These
secretions contain chemicals that destroy bacteria and fungi. Saliva and tears
may also contain substances that inhibit or destroy pathogens.
Antigens:
 Antigens are defined as any substance that the body recognises as being
foreign to an organism’s own body. They are protein molecules that trigger
an immune response. Each pathogen has its own antigen.
Why organ transplants trigger an immune response:
 Antigen-antibody responses result in rejection of transplanted tissue. This is
because it is identified by the body as a foreign substance. This triggers the
immune response to attack as if it were a pathogen.
Defence adaptations:
 If foreign substances or microorganisms get past the first line of defence and
enter deeper tissue, they’ll trigger the second line of defence.
- Inflammation response:
 Inflammation of tissue is designed to isolate and destroy foreign particles and
prepares the tissue for healing.
- Phagocytosis:
 Phagocytes are cells that engulf and destroy microorganisms. This process is
carried out by some white blood cells, neutrophils and macrophages and is
important as the body’s immediate defence against infection.
- Lymph system:
 The lymph system returns intercellular fluid to the blood system, filters cell
debris and produces white blood cells responsible for the immune response.
They are found in the armpits, neck and groin and their enlargement is often
a sign of infection.
- Cell death to seal off pathogen:
 After phagocytes have destroyed an antigen, they die. For some pathogens,
macrophages and lymphocytes completely surround a pathogen so that it is
enclosed in a cyst, isolating the pathogen from its food supply, resulting in its
death.
A disease caused by an imbalance of micro-flora:
 Micro-flora is a pathogen, which usually attacks specific parts of the body.
 Crohn’s Disease is a chronic disease that causes inflammation in the
gastrointestinal tract. It affects the small intestine and the beginning of the
large intestine.
 The exact cause is unknown however factors include an autoimmune
reaction (when a person’s immune response attacks healthy cells), genetics
and environmental factors.
 Symptoms include diarrhoea, abdominal cramping and pain and weight loss.
Symptoms vary depending on the severity of the inflammation and where it
occurs along the gastrointestinal tract.
 Effects include bowel obstructions, anal fissures and ulcers in the
gastrointestinal tract, which can be fatal if they rupture.
MacFarlane Burnet’s work in the middle of the 20 th century contributed to a better
understanding of the immune response and the effectiveness to immunisation
programs
 The ability of an organism to prevent or overcome infection by a pathogen is
through natural resistance and acquired immunity.
 MacFarlane Burnet developed the theory of clonal selection, which explains
how the immune system can defend the body against many different
antigens. This developed into the theory that non-self cells could be placed
into an organism and the body’s immune system would learn to recognise
them as self, paving the way for organ transplants.
Components of the immune response:
 Antibodies are proteins that the body produces when it detects antigens.
Each different antigen stimulates the production of its own specific antibody.
Antibodies join with the antigen so that they are clumped together and can
be recognised and destroyed more easily by macrophages.
 B-cells are a special kind of lymphocyte produced in the bone marrow. When
a B cell recognises an antigen, it divides repeatedly to produce a mass of
identical cells that work as antibody producers.
 T-cells are another kind of lymphocyte that is passed through the thymus
gland. Some T-cells produce toxic substances that destroy cells that have
been invaded by a virus. Others help the B-cells to divide rapidly.
The immune response in the human body:
- The interaction between B and T lymphocytes:
 T cells influence and help B cells. Both B and T lymphocytes interact as they
are both attacking the same antigen.
- The mechanisms that allow interaction between B and T lymphocytes:
 Mechanism 1: the T cell produces a soluble factor after interaction with an
antigen. The B cell reacts with the soluble factor and the specific antigen to
become a functional antibody-producing cell.
 Mechanism 2: this is based on cell contact between the T cell and the B cell.
This close contact comes about because of interaction with the antigen. This
contact allows the T cell to signal the B cell to become a functional antibodyproducing cell.
- The range of T lymphocytes and the difference in their roles:
 Killer T cells (Tc cells) produce cytotoxins that destroy or kill the infected cell.
They recognise and bind to antigens, destroying them directly.
 Helper T cells (Th cells) secrete chemicals that stimulate cloning in B and T
cells, enhancing antibody production by B cells.
 Memory T cells remain in the body and reactivate quickly with subsequent
infections by the same antigen
 Suppressor T cells stop the reaction when the antigen is destroyed
How vaccinations prevent infection:
 Artificial acquired immunity is called immunisation.
 Vaccinations involve the injection or ingestion of weakened or non-virulent
strains of microorganisms. It stimulates a person’s own immune system to
develop resistance.
 Vaccinations introduces antigens into the body so that B cells are activated to
produce large amounts of antibody and B cells that are stored in the lymph
system are ready for a future attack by a particular pathogen.
The effectiveness of vaccination programs:
 Vaccines are amongst the cheapest and safest methods for preventing
disease. Much of the world however remains unimmunized, with an
estimated 6-8 million children that die every year from disease that could
have been prevented by early immunisation.
 Despite this, vaccination programs, particularly in developed countries, have
stopped the spread and occurrence of once common diseases.
Smallpox:
 In 1796, Edward Jenner developed a vaccine against smallpox through
transferring the cowpox virus (less severe cousin of smallpox) from a dairy
milkmaid to an 8yr old boy, developing immunity to the deadly disease.
 By 1980, the World Health Organisation had declared the world free of
smallpox.
Diphtheria:
 In 1923, a vaccine was released however it took until the 1940s and 1950s for
the spread of the disease to shift from cyclical epidemics to occasional
outbreaks of low intensity.
 The vaccine injected is usually called DTP because it immunizes against
diseases such as diphtheria, tetanus and pertussis (whooping cough). In 1990,
the WHO stated that 80% of children were vaccinated against this disease.
Polio:
 Until 1955 when a vaccine was introduced, thousands of children in
industrialised countries became crippled with the disease.
 By the 1960s, an oral form of the vaccine was introduced and polio was
brought under control. It has now largely been eradicated from most part of
the world except parts of Asia and Africa. In 2005, there were 2033 cases
reported to WHO worldwide across 188 countries and a 95% vaccination rate
across 184 countries.
The suppression of the immune response in organ transplant patients:
 When an organ is transplanted, it is recognised by the immune system as
non-self. The body then attacks the new organ as if it was an invading
pathogen. T cells are the main cell type responsible for the rejection of
transplanted tissue.
 To overcome this problem, transplant patients are given powerful drugs to
suppress their natural defences. This can lead to susceptibility to infection for
the patient, so antibiotics are also given to the transplant patient.
Epidemiological studies involve the collection and careful statistical analysis of
large quantities of data. Such studies assist the causal identification of noninfectious diseases
The main features of epidemiology:
 Epidemiology is the study of epidemics, especially by looking for common
factors in populations affected by the disease. Their work can support
vaccination programs for controlling infectious diseases, but commonly it
relates to risk factors for non-infectious diseases.
 Epidemiology studies may be descriptive or analytical. There are three types
of these studies: a case study, a cohort study and a randomized study.
 Factors of a good epidemiological study include:
o Statistical association between the factor and disease
o Consistency across the study
o The related material used in the study confirms the result
 Lung cancer as an example: In the past, there were some epidemiological
studies that found a protective effect associated with beta-carotene.
However, when investigators undertook a double blind randomized
controlled trial, they found that beta-carotene increased the risk of mortality
for patients who were at risk of developing lung cancer.
The relationship between smoking and lung cancer:
 Doll and Hill in England and Hammond and Horn in the US established that
cigarette smoking markedly increased the chances that a person would
develop lung cancer.
 Other evidence comes from comparisons of trends in smoking rates across
sexes and trends in lung cancer. More males smoked and more males had
lung cancer. Male smoking rates declined before the rate declined in females.
 The NSW Cancer Council reports the following research:
o Smoking is a major cause of lung cancer
o Workers exposed to industrial substances such as asbestos either
have a significantly higher risk of developing lung cancer
o There is a link between passive smoking and lung cancer
o In 2012, 59% males and 41% females were diagnosed with lung
cancer. Lung cancer is up 200% in women.
o It is projected that one in 30 Australians will develop lung cancer by
the age of 75
o There has been a research link between smoking and lung cancer
however manufacturers are unable to accept that it is a direct cause
and effect relationship and that smoking causes lung cancer.
The causes of non-infectious diseases:
 Inherited diseases are caused by genetic factors. An example is Down
syndrome, which is an inherited disease that is caused by the non-disjunction
of chromosome 21, resulting in three chromosomes and not the usual two.
Those with Down syndrome have characteristic appearances.
 Nutritional deficiencies can lead to obesity and malnutrition diseases. An
example is anorexia nervosa, the under-nutrition of a person, resulting in
rapid weight loss and nutritional deficiencies.
 Environmental diseases are sometimes associated with factors in the
environment that include high stress levels, noise, overcrowding, drugs and
pollution. An example is mesothelioma, which is caused by the exposure to
asbestos and patients don’t get any symptoms until 20 or 30 years after
exposure. There is no cure and treatment can only slow down the
progression of the disease.
Non-infectious disease
Occurrence and cause
Symptoms
Treatment/management
Haemophilia
Sex-linked genetic disease.
The gene that controls manufacture of
blood clotting proteins occurs on the sex
chromosomes. Males with this disease
don’t have the genetic information for
blood clotting.
Bleeding (haemorrhage) from minor
injuries or bleed for no apparent reason.
They bleed into joints causing severe
pain; excessive blood loss causes
deformed joints and can cause death.
The blood factor missing is injected into
the haemophiliac in concentrated form;
genetic counselling informs people of the
chances of having a haemophiliac child;
genetic engineering has made it possible
to clone sheep whose blood contains a
substance that can be used to treat
patients with haemophilia B.
Increased understanding has led to the development of a wide range of strategies
to prevent and control disease
The role of quarantine in preventing the spread of disease, plants and animals in
Australia:
 Seeks to prevent the entry of harmful disease in Australia to stop the spread
of diseases within Australia.
 Quarantine regulations have prevented the entry of foot and mouth disease,
which has the potential to devastate the livestock industry. Within Australia,
some areas are free from certain diseases such as the bunchy top virus in
bananas.
 Quarantine laws to prevent the spread of the disease have restricted
movement of plant materials, such as plant and fruit stock, across regions of
Australia. As a further quarantine method, fruit-fly zones have been declared,
meaning there is no chance of fruit flies in any of Australian produce.
Pathogens and insect pests:
 Plants diseases include plant rust, black spots (mould), bugs (mites, aphids)
and damping off, caused by fungus. Symptoms include discolouration, holes
in leaves and powdery mildew.
 Aim: to observe plant shoots and leaves and detect evidence of pathogens
and insect pests.
 Method: collect a range of garden plants and observe them using a binocular
microscope.
 Results: many older varieties of lilly-pilly have obvious lumps on the leaves
called pimple gall and also deformed new growth. This is the effect of
psyllids. Black inky marks on the leaves of kangaroo paw plants are evidence
of a fungus that occurs particularly in moist conditions.
 Conclusion: discolouration of leaves, deformation of leaves, irregular shaped
leaves and furry white growth on the base of shoots are evidence of insects
and pathogens.
The effectiveness of quarantine:
 Strict quarantine controlling entry of plants and fruits into Australia has
prevented the entering and impact of the bacterial disease fire blight on the
Australian pome fruit industry.
 Quarantine however, was actually blamed for the rapid spread of equine
influenza through horses in NSW and QLD in 2007. Despite the fact that all
horses were retained and tested, the disease rapidly spread into police
horses and racehorses. It is positive that quarantine originally detected the
virus and placed restrictions on horse movement, but the failure to prevent
the spread is very disappointing and costly.
Strategies for controlling and/or preventing disease (pesticides):
 The use of pesticides helps control insect-borne diseases. Insects like
mosquitoes are vectors of diseases such as malaria, dengue fever and West
Nile Virus.
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Initially, the pesticide DDT was used, but there is now an increased
awareness of the risk of chemical pesticide use and there are strict guidelines
governing the pesticide used and the manner of its use.
Some pesticides target the mosquito larvae. They can be either biological
(such as toxin from specific bacteria that is lethal to mosquito larvae but not
to other organisms) or chemical products such as insect growth regulators,
surface films or organophosphates.
They are applied directly to water sources that hold mosquito eggs and
larvae. Adult mosquitoes can be killed by pesticides in hand-held sprayers, in
truck-mounted sprayers or by using aerial spraying.
The shift from treatment and control to management or prevention:
 Genetic epidemiology will contribute to the discovery of new drug
treatments that could be tailored to an individual’s genetic make-up as well
as the prediction of an individual’s future likelihood of getting a particular
disease. This will continue to change the emphasis of health care from
treatment to prevention.
 One example of the changes in methods has been the response to the avian
influenza (bird flu). We have become increasingly conscious of the ability of
viruses to change and to transmit across species. Bird mobility has a major
impact on the effectiveness of quarantine to prevent the spread if this
disease, at least among bird populations.
 Eventhough the deadly H5N1 avian influenza is extremely rare in humans;
between 2004 and 2005 there were 69 confirmed cases and 46 deaths from
the virus reported to the WHO. By 2005, the first vaccine was being trialled
amongst humans to prevent a further spread of a disease.
 The WHO has a website specifically to give updated information to the public
ad health professionals called ‘EPR – Epidemic and Pandemic Alert and
Response’. International health regulations were revised in 2005 to approach
to the prevention, detection and timely response to any public health
emergency of international concern.