module 7

Infectious diseasestudent notes

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Module 7: Infectious Disease

Content Focus

This module examines the treatment, prevention and control of infectious disease both locally and globally. It includes study of the human immune system and its response to an infectious disease.

The value of studying infectious disease and its causes and effects is highlighted by the cost to humans in terms of losses in productivity and production and the impact on overall health. The module also considers medical and agricultural applications that draw on the work of a variety of scientists.

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Causes of Infectious DiseaseInquiry question: How are diseases transmitted?

Students:● describe a variety of infectious diseases caused by pathogens, including microorganisms,

macroorganisms and non-cellular pathogens, and collect primary and secondary-sourced

data and information relating to disease transmission, including:

– classifying different pathogens that cause disease in plants and animals

Disease can be defined as “any condition that disturbs the normal functioning of the

body”.

A pathogen or infectious agent is a biological agent that causes disease or illness to

its host.

Pathogen Characteristics Example3

Prion Defective proteins: proteinaceous infectious particle

Minuscule Not cellular No nucleic acids Causes degeneration of brain

tissue Diseases can be both hereditary and infectious

Fatal Familial Insomnia

Virus Tiny: 30 to 300 nm Not cellular Can only reproduce using

host cells Can be crystallised

Influenza

Bacteria Small: 0.5 to 5 µm Cellular Prokaryotic: no membrane

bound organelles Single strand of DNA Reproduce by binary fission

quickly inside a host Waste products (toxins) often

harm host Classified by shape

Tuberculosis

Protozoa

Small: 2 to 1000 µm Eukaryotic: membrane-bound

nucleus No cell wall Many are free-living Classified by the way they

move

Amoebic dysentery

Fungi

Range in size, unicellular to multicellular

Eukaryotic: membrane-bound nucleus

Cell wall No chloroplasts Saprophytic (living on dead

matter) or parasitic

Thrush

Macro-parasites

Visible by the naked eye Endoparasites or exoparasites Endoparasites usually have

long association with host Ectoparasites usually have

brief association with host

Tapeworm, lice

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Prion

Virus

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Bacteria

Protozoa

Investigation 10.1

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– investigating the transmission of a disease during an epidemic– investigate modes of transmission of infectious diseases, including direct contact,

indirect contact and vector transmission

Epidemic

An epidemic is a widespread occurrence of an infectious disease in a community at

a particular time.

Pandemic

A pandemic is when the disease is prevalent over a whole country or the world.

Modes of transmission of infectious disease.

Transmission of infectious diseases involves the carrying or transfer of a pathogen

from an infected host to a non-infected organism.

For a disease to spread between organisms, a “chain of infection” must be present.

This chain has three elements:

1. A host that is susceptible to the disease2. A pathogen that is capable of causing the disease3. A mode of transmission: a way for the pathogen to get from host to host

There are three models of transmission, or ways that a pathogen can get from host to

host:

1. Direct contact: transfer of the pathogens via exposure to infected skin or body

secretions

2. Indirect contact: transfer of the pathogen to a new host via a non-living host

3. Vector transmission: transfer of the pathogen via another organism such as an

arthropod

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Direct ContactTransmission by direct contact occurs when there is physical contact between the

host and a non-infected organism.

Contact between organisms of the same generation, or between organisms that are

non-parent and child, is known as horizontal transmission.

Contact between offspring a parent is known as vertical transmission.

Physical contact includes:

Touching

Sexual contact

Kissing

Contact with the nasal or oral secretions

Biting

Direct contact with any blood or other body fluids

Direct contact with wounds

Prenatal all perinatal transmission

STI’s

Indirect Contact

Transmission by indirect contact occurs when the host organisms have no direct

contact with each other.

Infection occurs from a reservoir created by the host outside itself, such as

contaminated materials, surfaces or objects.

A fomite is in the object or substance that carries infection.

Some indirect means of transmission include:

Airborne transmission, e.g. Coughing or sneezing

Touching an infected surface

Contaminated food or water

Infected surgical instruments

Vectors transmissions through arthropods such as mosquitoes, ticks and fleas

Measles virus from infected droplets such as from body fluids

Gastroenteritis, for example, caused by the bacterium E. coli

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Diseases spread by vector transmission include:

Chagas disease – also termed American trypanosomiasis is an infection caused by

a protozoan parasite, (Trypansoma cruzi) that can result in acute inflammatory skin

changes (chagomas) and eventually cause infection and inflammation of many

other body tissues, especially those of the heart and intestinal tract.

Malaria

Dengue fever

Canine and feline heart worm

Hendra and Nipah viruses

Students read and summarise case study: equine influenza virus, page 334 of the textbook

Investigation 10.2

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– design and conduct a practical investigation relating to the microbial testing of water or food samples

Detection of microbes in food and water is not possible with the naked eye.

However, when microbes such as bacteria and fungi reproduce, they form clusters

which are visible to the naked eye. These clusters are called colonies.

Bacterial colonies can be smooth, glossy and coloured.

Whereas, fungal colonies are furry and large.

Bacterial colonies can be identified according to their:

Colour

Margin

Form (basic shape)

Elevation (shape of the cross-section)

Surface features (smooth, dull and wrinkled)

Investigation 10.3 page 338Check Your Understanding 10.1a p331 and 10.1b p339

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● investigate the work of Robert Koch and Louis Pasteur, to explain the causes and transmission of infectious diseases, including:– Koch’s postulates– Pasteur’s experiments on microbial contamination

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

Pasteur’s FlasksPasteur’s early research suggested the existence of spores. He hypothesised that

these spores were carried in air, where they were inactive. They developed into

active microorganisms when nutrients became available.

Pasteur designed the experiment as shown below. The flasks with the S shaped

neck allowed air to enter but dust and spores were trapped in the neck and could

not reach the broth. The other flask was directly open to the air.

Pasteur boiled the broth and subjected the glassware to steam to kill any microbes

present.

As Pasteur predicted the glassware with the S bend did not become contaminated

proving that the organisms that contaminated the broth must be carried in the air.

Pasteur’s flasks are still on display in the Pasteur Institute in Paris and after 150

years they are still not contaminated.

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Investigation 10.4 page 343

Koch’s PostulatesKoch developed a set of procedures to follow, which will definitely and scientifically identify the pathogen. These procedures are known as “Koch’s Postulates” and are still used today when previously unknown infectious diseases are discovered.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’s Postulates

The organism believed to be the cause of the disease must always be present

when the disease occurs.

The organism must be isolated from the host and grown in pure culture.

Organisms from the pure culture, when inoculated into healthy, suitable,

susceptible hosts must produce the disease.

The organism must be re-isolated, grown in pure culture and compared to the

organism first injected.

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Summary of Pasteur’s and Koch’s work

Louis Pasteur (1822-1895) Robert Koch (1843-1910)Created the science of microbiology Developed many bacteriological techniquesDemonstrated that microbes caused the souring of wine and beer (lactobacilli)

Developed the agar plate technique for growing microorganisms

Development of the process of pasteurisation to kill bacteria

Identified the bacterium Bacillus anthracis responsible for anthrax disease.

Conducted the swan-necked flask experiment to disprove spontaneous generation

Demonstrated that specific microbes are responsible for causing specific diseases

Established the germ theory of disease, that microbes caused disease Developed Koch’s postulates

Developed a vaccine for chicken cholera Identified the bacterium responsible for tuberculosis and cholera

Used Koch’s work on anthrax to develop a vaccine for anthraxDeveloped a vaccine against rabies and used it on humans for the first timeEstablished the principle of immunity and developed an effective way to prevent infectious disease

Check Your Understanding 10.2 page 344

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● assess the causes and effects of diseases on agricultural production, including but not limited to:

– plant diseases– animal diseases

Causes and effects of disease in agricultural production.

Culture involves cultivation of crops and pastures and the rearing of animals.

Infectious diseases in Australian agriculture

Two types of plant and animal diseases are of concern in agriculture in Australia:

1. Endemic diseases: these are diseases consistently present in a country or

region, such as bovine Johne’s disease in sheep and cattle and footrot in sheep.

2. Exotic (introduced) diseases: such foot and mouth disease, avian influenza and

bovine tuberculosis as examples.

The complex interplay of three factors may contribute to the development of

infectious disease in organisms of agricultural imports.

Host factors - susceptibility to disease, access to pathogens, concurrent disease

or poor nutrition leading to weakened immune response, drought and heatwave

stress on the host.

Pathogen factors – the pathogens availability, its ability to transfer between

hosts, as well as virulence factors including adhesion and invasion of host

tissues, and successful establishment inside host tissues.

Environmental Factors – overcrowding and lack of hygiene and to a build-up of

wastes, which provide a suitable environment for pathogen reservoirs

The favourable environment within the host for pathogens to establish and cause

disease.

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Students summarise case study: Footrot in sheep page 345

Factors contributing to the risk of infectious disease

Increased mobility of human populations

Rise of intensive and industrial types of agriculture.

Changing patterns of land use

Climate change

Antimicrobial resistance (e.g. Resistance to antibiotics)

Pesticide resistance

Loss of genetic diversity

Increasing the number of hobby farmers – if farmers with little experience in animal

husbandry or crop production

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Plant diseases of agricultural significance

Commercially grown plants in Australia include:

Grains

Fruits and vegetables

Fodder

Fibre

Horticultural plants

Forestry planets

The main causes of infectious diseases in plants include:

Fungi – are by far the most common cause of plant disease.

Terms such as rust, blight, smut and mildew are all fungal diseases in plants.

Reservoirs of fungal spores exist in contaminated seeds, farm machinery, and

soil and nearby weeds.

These pathogens can be transmitted by wind, water and direct contact with the

reservoirs.

Fungi move into plants through their stomata or other openings in the plant.

They damage the plant by destroying conducting tissues and absorbing nutrients

from the plants.

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Insects and mitesInsects and mites cause direct damage to plant tissue but can also act as vectors for

other pathogens.

Examples include aphids, fruit fly, citrus leaf miner and mealy bugs.

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Bacteria

Reservoirs of pathogenic bacteria may occur in soil, weeds, seeds and humans.

Bacteria need certain conditions to be to multiply and spread. These may include

humid and warm conditions.

An example is bacterial canker of tomatoes.

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Nematodes (Microscopic Worms)

Thousands of these live in the soil but only a few act as plant pathogens.

The nematodes attacks plant roots, creating galls and lumps.

The plants subsequently wilt, turn yellow and die.

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Viruses

Plant viruses are obligate (by necessity) intracellular parasites.

For example the tomato mosaic virus.

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The students summarise the case study: Panama disease of bananas page 349

Investigation 10.5

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● compare the adaptations of different pathogens that facilitate their entry into and transmission between hosts

Adaptations of pathogens to facilitate their transfer.

For a pathogen to successfully establish an infection, it must find a way to adhere

to the hosts cells, colonise the host tissues, and persist in the host long enough to

reproduce.

For an organism to cause disease it must:

1. Enter the host

2. Multiply within the host tissues

3. Resist or not stimulate host defence mechanisms

4. Damage the host

The following table summarises some of the strategies that the various cellular and

non-cellular pathogens use to gain access and colonise host tissues.

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Responses to Pathogens

Inquiry question: How does a plant or animal respond to infection?

Students:● investigate the response of a named Australian plant to a named pathogen through

practical and/or secondary-sourced investigation, for example:– fungal pathogens– viral pathogens

Students to complete Investigation 11.1

Immunity

Inquiry question: How does the human immune system respond to exposure to a pathogen?

Students:● analyse responses to the presence of pathogens by assessing the physical and chemical

changes that occur in the host animals cells and tissues

● investigate and model the innate and adaptive immune systems in the human body

● explain how the immune system responds after primary exposure to a pathogen, including innate and acquired immunity

Pathogens: a bacterium, virus, or other microorganism that can cause disease.

Antigens: are molecules which trigger an immune response e.g. bacteria, viruses

and a foreign marker on cell membrane.

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Lines of DefenceInnate Immunity

Innate immunity is present at birth and is genetically determined.

Its response to pathogens are non-specific, and include both physical and

chemical (first line of defence) as well as cellular responses (second line of

defence).https://www.youtube.com/watch?v=GIJK3dwCWCw

Adaptive Immunity

Adaptive immunity is the third line of defence.

This is a specific defence mechanism consisting of specialised cells that act if the

pathogen persists in its invasion.

https://www.youtube.com/watch?v=2DFN4IBZ3rI

First Line Defence mechanisms30

Barrier Method of defence

Skin

Tough physical barrier

Dry, outer layer of cells inhibits bacterial growth.

Oil and sweat glands produce antibacterial and antifungal substances.

Beneficial bacteria live off the oil secreted by sebaceous (oil) glands and produce acids that prevent pathogen growth.

Mucus membranes

Pathogens get caught in mucus which is coughed up or swallowed.

 Contains antibody to prevent pathogens attaching.

Harmless microbes produce substances that inhibit growth and entry of pathogens.

Cilia Move mucus containing pathogens out of

the lungs

Chemical barriers – urinary and vaginal tracts

Acidic conditions inhibit growth and entry of pathogens.

Chemical barriers – alimentary canal

Acid of the stomach is intolerable for many pathogens.

Other pathogens cannot tolerate the basicity of the intestines.

Other body secretions – Saliva

Washes bacteria from between teeth

Contains chemicals to destroy microbes

Other body secretions – tears

Contains enzyme lysozyme that destroys some bacterial cell walls

Wash pathogens are away from eyes

Other body secretions – urine

Acidity prevents growth of pathogens

Flushes and cleans urinary system

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Second Line of DefenceAdaptation Method of defence

Inflammation response

Tissue around the wound becomes hot to inhibit activity of pathogens by denaturing the enzymes of the pathogen. Chemicals such as histamine are released, causing the tissue becomes swollen as capillaries swell to increase blood circulation to the area, allowing more white blood cells to be released to attack pathogens.

Phagocytosis

A phagocyte is a cell that can flow about another cell and engulf it. Neutrophils, manufactured in the bone marrow and found in blood-lymph and body tissues, ingest bacteria and the enzymes break down the bacterium. Macrophages engulf foreign particles and poisons, common in the liver and lymph glands, and are more commonly involved in fighting off long infections.

Lymph system

Lymph nodes filter the lymph fluid and remove pathogens, dead cells and other debris. Lymph nodes contain phagocytes to destroy any foreign material.

Cell death

If other responses cannot control the pathogen, a layer of dead cells (granuloma) is formed around infection site, followed by a layer of macrophages. Pathogens eventually die and are consumed by macrophages.

Third Line of Defence - Acquired Immunity32

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.

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Description Role

Antibodies

Proteins that the body produces when it detects specific antigens

Different antigens stimulate the production of different corresponding antibodies

Join with antigens, causing them to clump together to form an antibody-antigen complex

Antigen-antibody complex is more easily recognised and destroyed by macrophages than antigens alone

B cell

Special kind of lymphocyte

Produced in bone marrow

Control antibody-mediated immunity

When a B cell recognises an antigen, it is cloned to produce a mass of identical cells.

The B cells work as antibody producers (plasma cells) or memory B cells which provide long-term immunity.

T cell

Special kind of lymphocyte

Produced in bone marrow

Mature in thymus gland

Control cell-mediated immunity

Cytotoxic T cells produce toxic substances that destroy cells that have been invaded by a pathogen. They defend the body cancer cells and transplanted tissue.

Helper T cells help B cells divide rapidly.

Suppressor T cells turn off the immune response and suppress the production of antibodies when they are not needed.

Memory T cells recognise the antigen if it is re-introduced, providing long-term immunity.

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Both B and T lymphocytes attack the same antigen and must interact.

Antigen presenting B cells are inspected by helper T cells.

Helper T cells stimulate B cells and T cells to clone.

Helper T cells stimulate the production of antibodies by plasma cells.

Suppressor T cells stop the production of B cells and T cells when the antigen is

destroyed.

Your body can produce the most effective weapons against the invaders, which

may be bacteria, viruses or parasites. Other types of T-cells recognise and kill

virus-infected cells directly. Some help B-cells to make antibodies, which

circulate and bind to antigens.

With the help of T-cells, B-cells make special Y-shaped proteins called

antibodies. Antibodies stick to antigens on the surface of germs, stopping them

in their tracks, creating clumps that alert your body to the presence of intruders.

Your body then starts to make toxic substances to fight them. Patrolling

defender cells called phagocytes engulf and destroy antibody-covered intruders

Mechanisms that allow interaction between B and T lymphocytes

Interaction occurs through cell contact or the production of chemicals by the T cells e.g. interleukins which cause B cells to divide.Helper T cells (T4 cells) are able to recognise “self” molecules that mark the surfaces of B cells, preventing T cells from attacking the person’s own B cells if the B cell has an antigen on its surface.

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Range of T lymphocyte types and the difference in their roles

Type of T lymphocyte Role

Killer (cytotoxic) T cells (Tc cells)

Attack and destroy body cells that have been infected by an antigen by producing toxic chemicals (perforins) which cause the cell membrane to rupture and the cell lyses

Helper T cells (T4 cells)

Secrete chemicals such as lymphokines and interleukins that stimulate cloning in B and T cells and stimulate macrophages for phagocytosis

Memory T cellsRemain in the body and reactivate quickly with subsequent infections by the same antigen

Suppressor T cells (T8 cells)Stop the production of B and T cells and suppress antibody production when the antigen is destroyed

Prevention, Treatment and Control

Inquiry question: How can the spread of infectious diseases be controlled?

Students:● investigate and analyse the wide range of interrelated factors involved in limiting local,

regional and global spread of a named infectious disease

Factors involved in monitoring and control.

The three main factors to consider in monitoring and control:

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Local factors

Local factors include neighbourhoods, towns, cities etc.

Regional factors

The United Nations divides the world into five regions: Africa, the Americas, Asia,

Europe and Oceania.

Global factors

The global factors encompasses the whole world. Increasing the amount of people

around the globe has increased the difficulty in limiting the spread of infectious

disease.

Factors involved in disease transmission.

The causes of the spread of disease can be multi-factorial involving local, regional

and global factors.

Pathogen factors

Some pathogens are virulent (and can cause disease in small numbers. (A virulent

disease is dangerous and spreads or affects people very quickly)

Other pathogens need to be present in large numbers to cause of these rates.

Some pathogens form reserves in food, water or the environment.

Others must be a transferred directly from host to host.

Host factors

The fact that the host is invaded by a pathogen does not mean that the host will get

the disease.

The immune system of the host may prevent the disease from developing.

The health of the host also plays a role in the development of the disease.

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The environmental and geological factors

Certain environments may predispose the spread of infectious diseases.

Pathogens may build-up a large reservoir in certain environments which produces a

greater risk of outbreaks. For example, in areas of natural disasters such as

earthquakes and floods.

Societal factorsSocietal factors may further enhance the spread of disease.For example diseases such as chickenpox and measles can return in society due to anti-vaccination campaigns.

Case Study P451Students read and summarise Pages 451 to 453 in context of the syllabus dot point.

● investigate procedures that can be employed to prevent the spread of disease, including but not limited to:

- hygiene practices- quarantine- vaccination, including passive and active immunity - public health campaigns- use of pesticides- genetic engineering

HygieneHygiene can be divided into two types: personal and community hygiene.

Personal hygiene involves keeping the body and any openings on it clean.

This reduces the risk of pathogens and entering the body or the transmission of

pathogens to others.

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Community hygiene

Community hygiene helps prevent the build-up of pathogenic organisms in a

community.

Community hygiene includes the following measures:

Sewage and garbage disposal

Sterilization and disinfection of equipment in medical practices.

City planning

Clean food and water prevents the transfer all pathogens

QuarantineDue to Australia’s geographical isolation it remains one of the world’s countries

least affected by serious diseases and pests.

The Department of Agriculture and Water Resources (DWAR) is responsible for

Australia’s biosecurity.

The role of quarantine is to minimize the risk of exotic pests and diseases entering

Australia, in order to protect our native flora and fauna, our agricultural industries

and our health.

Plants and animals that are placed into quarantine when entering Australia. Sick

passengers are also quarantined when entering Australia. The Australian

Quarantine and Inspection Services (AQIS) is responsible for this.

VaccinationVaccination involves the introduction of a vaccine (A vaccine is a biological

preparation that provides active acquired immunity to a particular disease.)

Immunization is the process in which the body reacts to a vaccine by going through

the immune response.

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Active acquired immunity

Active acquired immunity is when the immune response occurs and memory cells are

produced.

It can be naturally induced or be artificially induced (through vaccination).

Vaccines contain cultures of micro-organisms, which may be either:

1. Living but attenuated (weakened) and therefore harmless, e.g rabies and

measles

2. Dead, e.g typhoid and whooping cough

Passive acquired immunityPassive acquired immunity involves the introduction of the antibodies (the

immunoglobulins) into the body to prevent a disease from developing.

The antibodies have been produced by another organism that has had the disease.

For example, if you have been exposed to hepatitis A, you may be given injections

of the antibodies to prevent you from catching the disease. This is the only a short

term immunity.

Public health campaignsThe approach to controlling infectious diseases can be that and down into four

categories, known as RICE.

Resolution of governments and health organizations to find solutions to

infectious diseases.

Information in the form of epidemiological studies and scientific studies of

the pathogen and it’s mode of transmission so that the solution it is based on

accurate data.

Coordination of efforts on a local, regional and global scale so that resources

are used efficiently.

Education of human populations on a local, regional and global scale

regarding factors affecting infectious disease transmission.

Notifiable diseases include measles, botulism, cholera, meningococcal

infection, pertussis (whooping cough) and malaria.

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Use of pesticides

Pesticides are chemicals used to kill the pests of plants and animals, including

the vectors that transmit them.

Pesticides can be classified into three groups:

1. Insecticides – kill insects e.g. DDT

2. Fungicides – kill fungal pathogens

3. Herbicides – kill weeds and sometimes or plants

Genetic engineering

Genetic engineering involves altering the genetic composition of an organism.

This can give the organism resistance to disease or other designed characteristics.

Procedures used include gene cloning, forming transgenic species and genetic

engineering to give disease resistance, (for example BT cotton).

Check your understanding 13.2 b 1, 2, 3, 5, 6 & 7

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● investigate and assess the effectiveness of pharmaceuticals as treatment strategies for the control of infectious disease, for example: – antivirals– antibiotics

Pharmaceuticals for controlling infectious diseaseChemotherapy is a general term that means the use of any drug to treat any disease,

(it does not just mean the treatment of cancer).

Antimicrobial agents are designed to control infectious diseases caused by microbes.

The main classes of antimicrobials are:

Antiviral medicationsViruses enter as cells which then reproduce the virus.

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The genetics of viruses vary in the following ways:

They may contain DNA or RNA

The antiviral medications are used to control viral infections.

They do not kill viruses, but inhibit their development inside affected cells.

They do not do cure the disease but simply slow down its progress, allowing the

body’s natural defences to take over.

They stop the spread of viral diseases, and therefore, are a useful addition to the

control of the epidemics and pandemics.

The viruses most commonly targeted by antiviral drugs include:

HIV

Seasonal influenza A

Herpes

Hepatitis B and C

Three antiviral medicines to treat influenza and registered for use in Australia:

Oseltamivir (Tamiflu ®)

Zanamivir (Relenza ®)

Amantadine (Symmetrel ®)

These compounds are effective against seasonal influenza A strains.

Efficacy is important, (efficacy of a medication is its ability to produce the desired

outcome.), as nations stockpile the medications in case of a pandemic.

These drugs have greater efficacy when taken early in the course of the illness.

Antibiotics

Antibiotics are used to control bacterial infections.

They work by either killing or slowing down the growth of bacteria.

Antibiotics are not effective against viruses.

Antibiotics are most effective when:

They are used solely for the treatment of bacterial infections.

Bacterial antibiotics are used to kill rather than inhibit growth of the bacteria,

(penicillins and cephalosporins).

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Narrow spectrum antibiotics are chosen that target the specific pathogen.

They are able to get to the site of the infection and kill the bacteria.

The whole course is taken to reduce the risk of bacterial resistance.

A Gram stain and culture and sensitivity tests are done to ensure that the

appropriate antibiotic has been chosen.

(Gram staining is a common technique used to differentiate two large groups

of bacteria based on their cell wall constituents.

Check Your Understanding 13.3 p451 1, 2, 4, 5

● investigate and evaluate environmental management and quarantine methods used to control an epidemic or pandemic

Environmental management and quarantine methods.Case study: Ebola virus disease 2014 – 2016Students read and summarise pages 451 to 453

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● interpret data relating to the incidence and prevalence of infectious disease in populations, for example:– mobility of individuals and the portion that are immune or immunised – Malaria or Dengue Fever in South East Asia

The accumulation of real-time data on infectious diseases is currently managed in

Australia by both Federal and State/Territory governments.

The constant threat of new and emerging diseases as well as the re-emergence of

old diseases (e.g. tuberculosis and measles) requires a robust system of data

gathering and analysis.

The type of data that must be collected includes:

Incidence and prevalence of the disease – determines what pathogens are

present in a population.

Mobility of the population

Percentage of the population that is immunised against an infectious disease.

Incidence

The incidence of an infectious disease is the number of new cases occurring

during a specified time.

To calculate the incidence of a disease as a percentage, the following formula can

be used:

For example, a survey was conducted in a school with 1000 students. Over the winter period 150 students contracted influenza. The prevalence is:

Prevalence = 150 x 100 = 15%1000

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Mobility

The mobility of a population determines the rate at which a disease will spread.

The rate of immunisation of a population is a key factor in analysing data relating

to infectious disease.

When a significant proportion of the population have been immunised, this

creates herd immunity.

Herd immunity relies on high numbers of individuals being vaccinated, to reduce

the chances of unvaccinated individuals coming into contact with the disease-

causing microbe.

When the population has herd immunity, everyone in that population, including

unvaccinated individuals, are protected against epidemics.

- Malaria or Dengue Fever in South East Asia

Investigation 13.5aCheck Your Understanding 13.5 p457 1, 3, 5

● evaluate historical, culturally diverse and current strategies to predict and control the spread of disease

Historical Control of a Disease Outbreak

Investigation 13.6

Cultural Control of the Spread of Disease.

Culture refers to the integrated patterns of human behaviour, including the

language, thoughts, communications, actions, customs, beliefs, values and

institutions of racial, ethnic, religious or social groups.

In 2014 control of the Ebola outbreak in South Africa was made it difficult

through local culture. The traditional ritual of paying respects to the deceased

through close contact with the corpse promoted the spread of the disease.

Control measures needed to include educating the public to abandon these

traditional cultural belief systems.

Check Your Understanding 13.6

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● investigate the contemporary application of Aboriginal protocols in the development of particular medicines and biological materials in Australia and how recognition and protection of Indigenous cultural and intellectual property is important, for example:

– bush medicine– smoke bush in Western Australia

Students Read and Summarise p 459 to 460“Aboriginal protocols in the development of medicines.”

Investigation 13.7 Students produce the table in the method.

For example, The Emu bushhttp://anpsa.org.au/APOL22/jun01-2.html

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