HSC Biology Module 7

'Germ theory of disease'

The belief that disease and decay are the product of living organisms was unknown to people, who still believe in spontaneous generation: that living organisms could arise from inanimate materials such as rotting meat.

Infectious disease

Caused by another organism or infective agents (pathogen).

Non-infectious disease

Doesn't involve the transfer of pathogens between the host.

Prions

An abnormal protein that is capable of causing degenerative diseases of the nervous system that do not contain any genetic material. Pathogenic prions cause disease by inducing abnormal folding patterns in the normal proteins that they come in contact with. The abnormal proteins are deposited within the central nervous system and other organs. Diseases caused by pathogenic prions are known as transmissible spongiform encephalopathies (TSEs). They are called 'spongiform' diseases because the brain tissue is full of holes, resembling a sponge.

Example: mad cows disease.

Viruses

It is a non-cellular pathogen and consist of a protective protein coat (called a capsid) that encloses the genetic material, which may be DNA or RNA - this is the infectious part of the virus that contain RNA are known as retroviruses. The viral protein coat contains chemicals that allow the virus to attach to the surface of the host cell. Once the virus has attached to a cell, it enters and takes over the cell's reproductive mechanisms, making many copies of itself. The host cell becomes so full of copies of the virus that it dies and bursts, releasing the new viruses, which repeat the replication process in other cells.

Example: influenza.

Bacteria

Are single-celled prokaryotic organisms that have a cell wall but no membrane-bound nucleus or organelles. They reproduce asexually through binary fission and can be classified according to shape; spherical = coccus, rod - shaped = bacillus, spiral = spirillum, comma -shaped = vibrio.

Bacteria that cause disease produce toxins or chemicals that are harmful to the host's body or damage the host tissue directly. Some bacteria can form endospores (a tough, waterproof external layer) which allows the bacteria to resist heat, chemicals and desiccation.

Example: whooping cough.

Protozoa

Are single-celled eukaryotic organisms that are classified along with algae and slime mould in the kingdom protista . They have a membrane-bound nucleus, membrane-bound organelles and cell membrane, but no cell wall. Often reproduce by the process of binary fission. Most are free-living and do not cause disease.

Type of classification: flagellates which propel by a long whip-like tail called a flagellum, amoebae use projections of the cytoplasm to move around, ciliates have many hair-like projections, called cilia, which propel to protozoan bu beating rapidly , sporozoa are protozoans that do not have structures for motion and reproduce by releasing spores.

Example: malaria (anaphalis)

Fungi

Are eukaryotic organisms; they are heterotrophic - have a cell wall with no chlorophyll. Most are saprophytic. They live on dead plant and animal materials . They can be unicellular or multicellular - some fungi like yeast reproduce asexually whilst other fungi may reproduce sexually and asexually.

Fungi infections can be; cutaneous = outer layer skin, subcutaneous = beneath the skin surface, systemic = affecting internal organs

Example: tinna

Macroparasite

Visible to the naked eye. Multicellular eukaryotic organisms. Some cause disease directly, whilst others act as vectors . They are often classified into two groups based on where they live: endoparasites; live inside the body or ectoparasites; live on the outside of the body

Parasitic arthropods - they are invertebrates that have an exoskeleton and a segmented body; including insects and arachnids. They are ectoparasites. They cause skin irritations, act as vectors for other pathogens and contribute to blood loss and concurrent infections and treatment involves generally involves chemicals. Fleas, ticks, lice, mites, flies, mosquitoes are all examples

Example: tick or tapeworm

Direct transmission of infectious disease

Person-to-person contact, droplet spread.

Indirect transmission of infectious disease

Airborne transmission, contaminated objects, food and drinking water, animal-to-person contact, vector-borne.

Vector transmission

Indirect transmission of pathogens. Occurs through arthropods such as certain species of mosquitoes, sandflies, ticks, fleas and flies, or through infected aquatic snails. It usually involves a bite from an arthropod that is bloodsucking and transmits the pathogen during a meal, although in some cases, animals swallow the arthropod in the act of grooming themselves.

Airborne - adaptations to facilitate the transmission of pathogens

Can remain suspended in the air for long periods of time, resists drying out , can cause sneezing or coughing, able to tolerate a wide range of oxygen concentrations.

Waterborne - adaptations to facilitate the transmission of pathogens

Can colonise and proliferate in water, modified outer surface structures to allow motility, able to tolerate high salinity, many can't be destroyed simply by boiling water.

Faeco-oral - adaptations to facilitate the transmission of pathogens

Very stable in varied environments, antimicrobial resistance gene.

Soil-borne - adaptations to facilitate the transmission of pathogens

Form endospores to resist desiccation, stable in the environment under a range of conditions, grow mainly in the root zone, only a few bacteria are soil-borne pathogens of plants.

Blood-borne - adaptations to facilitate the transmission of pathogens

Takes advantage of altered features or red cells to facilitate growth and development.

Vertical / sexual - adaptations to facilitate the transmission of pathogens

Transmission across placenta, uterine invasion, unprotected sexual activity, consumption of placenta but other animals in the wild, aerosolised from afterbirth.

Koch

Developed the agar plate technique for culturing microorganisms. From his research, he determined that each disease is caused by specific microorganisms; a principle he used to identify the specific microorganisms that were responsible for a disease.

Koch's postulate - The same microorganism must be presented in every diseased host. The micro-organism must be isolated and cultured in a laboratory and accurately described and recorded. When a sample of the pure culture is inoculated into a healthy host, this host must develop the same symptoms as the original host. The micro-organism must be able to be isolated from the second host and cultured and identified as the same as the original species.

Pasteur

Is credited with creating the science of microbiology. He identified microbes as the agents responsible for spoilage during the production of wine, beer and vinegar, leading to pasteurisation.

His germ theory; support through his swan-neck flask experiment.
He contributed to the development of vaccines for fowl cholera. He predicted that spontaneously generated was incorrect and microbes are present in the air and that food spoils when these microbes land and become active; disproved spontaneous generation; microbes were airborne, developed the world's first attenuated vaccine, demonstrated that fermentation was caused by living organisms; yeast, invented pasteurisation; heating liquids at high temps to kill micro.

Adaptations of pathogens to facilitate their transfer

For an organism to cause disease it must; enter the host, multiply in host tissues, resist or not stimulate hot defence mechanisms, damage the host.

Prions - adaptations to facilitate adhesion to and invasion of the host by a pathogen

Secreting factors that enable prions to invade follicular dendritic cells in lymphoid tissue. From lymphoid tissue, they invade nervous tissue through the autonomic nerves and travel to the brain, 'piggyback' other proteins such as ferritin to facilitate movement.

Viruses - adaptations to facilitate adhesion to and invasion of the host by a pathogen

Adhesion - must enter the nucleus of the host cell to facilitate replication of the viral genome. Viral surface proteins adhere to host cell surface receptors and co-receptors.

Invasion - enveloped viruses are encoded within an envelope endosome formed from the host cell membrane as they move into the cell. Non-enveloped viruses form a pore in the host cell membrane and deliver the viral genome through it.

Bacteria - adaptations to facilitate adhesion to and invasion of the host by a pathogen

Adhesion - pili and fimbriae, adhesion of the surface of the bacterial cell can resist washing action of secretions, translocation of bacterial proteins cause host cell membrane engulfment of bacteria.

Invasion - enzymes break down cell contents, capsules resist phagocytosis by host, chemical strategies to destroy host immune defences, toxins are secreted to the damage host cell.

Protozoan - adaptations to facilitate adhesion to and invasion of the host by a pathogen

Microtubule protrusion into host cell facilitates entry and formation of a vacuolar membrane gives protection from lysosomes. In receptor-mediated attachment, recruits lysosomes fuse with the cell membrane and pathogen enter vacuole made of lysosomal membrane and then deactivate lysosomal enzymes.

Fungus - adaptations to facilitate adhesion to and invasion of the host by a pathogen

Adhesion - assisted by cell wall or capsule molecules that permit adhesion to host cell

Invasion - thermotolerance; heat shock proteins are synthesised to cope with the body temperature, converts to parasitic yet when exposed to heat, cell wall and capsules protect fungi from being attacked, secretion of hydrolytic enzyme damages host cell and provides nutrients to fungus, evasion mechanisms; capsule production, suppression of cytokine production and reduce fungicidal power of macrophages.

Macroparasites - assisted by cell wall or capsule molecules that permit adhesion to host cell

Hookworms; secrete immunomodulatory proteins that reduce host cell immune response. Ticks; molecules are secreted when a tick bites into the skin to prevent vasoconstriction, preventing the host from forming a clot and initiating the inflammatory response.

Plants response to pathogens

Defences may be passive or active.

Passive defence - plants

Two major types; physical barriers and chemical barriers.

Physical barriers include things like thick cuticles, cell walls and small stomata, bark and vertical hanging leaves - inhibit pathogen entry.

Chemical barriers include things like the presence of chemical compounds in the tissue of plants, enzyme production and chemical receptors - inhibit pathogen entry.

Active defence - plants

Three major groups; pathogen recognition, rapid active response (minutes to hours), delayed active response (days).

Plant diseases

Typically caused by various fungi and bacteria - examples include panama disease is caused by a fungus (Fusarium oxysporum) and potato blight is caused by a fungus (Phytophthora infestans).

Fire blight - plant disease

A plant disease of pome fruit (apples, pears), found in nearly every apple producing country except Australia and Japan. It is caused by the bacterium Erwinia amylovora. It attacks blossoms, leaves shoots, branches, fruit and roots resulting in tissue death and bacterial ooze droplets on infectious tissues. Spread through rain, wind, insects and pruning tools. Prevention is the best management for it, done through: on-farm biosecurity to prevent entry, establishment and spread of pests and diseases amd ensuring all staff and visitors are instructed in and adhere to on-farm hygiene practices.

Animals response to pathogens

Innate immunity is present at birth and is genetically determined. It response to pathogens are non-specific and include the first line of defence and the second line of defence. All cell and defences involved are genetic and not adapted to specific infections.

Animal diseases

Typically caused by various viruses and bacteria - examples include newcastle disease is a viral disease and anthrax is caused by a bacterium (Bacillus anthracis).

Foot and mouth disease - animal disease

FMD is a highly contagious disease of cloven-hoofed animals (cattle, sheep, goat and pig). It also is excluded from Australia as a result of strict quarantine. FMD is caused by the foot and mouth disease virus (FMDV). It causes fever and blisters in the mouth and hooves, learning to serve production losses as even though the infected animal recovers, it is left debilitated.

Cause and effects of disease in agricultural production

Infectious disease in agriculture - two types of plant/animal disease;
endemic; disease constantly present within a country or region
exotic; disease that is introduced.

An interplay of three factors contributes to the development of infectious disease; host, pathogen and environmental factors.

Factors that contribute to the risk of infectious disease: increased mobility of the human population, rise of intensive and industrial type agriculture, changing patterns of land use, climate change, antimicrobial resistance, pesticide resistance, loss of genetic diversity, increase in hobby farmers, increase in use of aquaculture as marine and freshwater animal population decrease.

Fungi - cause of infectious diseases in plant in agriculture

Reservoirs of fungal spores exist in contaminated seeds, farm machinery, soil and nearby weeds, and are generally transmitted by wind, water and contact with the reservoirs through normal farming operations. Fungi enter plants through their stomata or any other opening caused by mechanical damage to the plant, such as pruning and insect bites. They damage the plant by destroying conducting tissues and absorbing nutrients.

Insects and mites - cause of infectious diseases in plant in agriculture

Insects and mites cause direct damage to plant tissue and act as vectors for other pathogens.

Bacteria - cause of infectious diseases in plant in agriculture

Reservoirs of pathogenic bacteria may occur in soil, weeds and seeds.
Humans can also harbour bacteria on their hands and equipment from previous work with a contaminated crop of plants. However, bacteria only multiply and spread when certain conditions are met. These include humid, warm weather, overcrowding of plants, inappropriate soil conditions (water, nutrients, pH and salinity) and poor air circulation.

Nematodes - cause of infectious diseases in plant in agriculture

The nematode attacks plant roots, creating galls and lumps. The plants subsequently wilt, turn yellow and die. The eggs of these nematodes can persist in the soil for a year and reinfect the next crop. The infestation can be dealt with by repeated cultivation of the soil and exposure to the sun, combined with the removal of residual root material after harvesting to reduce reservoirs of the eggs.

Viruses - cause of infectious diseases in plant in agriculture

Viruses are stable in the environment and can persist in plant material left over after cropping. They can also form a reservoir on contaminated equipment. Increased plant densities and frequent handling of plants by humans appear to play a role in its transmission.

Phytoplasma - cause of infectious diseases in plant in agriculture

They are transmitted from plant to plant by insect vectors and inhabit phloem tissue.

Abiotic factors that cause disease include...

Temperature variation, light availability, chemical agents, water quantity and quality, nutrients available in the soil.

Effects of infectious disease in plants

Biological effects on the plant, the social and economic effects on the farmer, the social and economic effect on the economy.

Effects of infectious diseases in farm animals

Death of affected animals, loss of appetite, the onset of weight in a short period of time, economic loss to the farmer, reduction of production and therefore reduction in profit, human illness and disease, the low growth rate in young animals, loss of fertility.

The first line of defence

Consists of a range of physical and chemical barriers that are non-specific and prevent the entry of pathogens.

Physical pathogens

Mucous membrane, cilia and peristalsis: Mucous membrane lines the respiratory, urinary and digestive tracts.

A layer of ciliated epithelial cells lines this mucous, secreting mucus that lubricates the layer below and traps any debris or microbes that enter the body This movement directs the and any trapped microbes out and away from the body's organs; i.e. sneezing.

Chemical pathogens

Stomach acid/enzymes, lysozyme, alkali pH in the small intestine

Chemical - Stomach acid and small intestine: Lysosomes within the saliva attack and perforate cell walls of many bacteria. The stomach contains hydrochloric acid which kills most microbes, preventing them from entering your body via food or water.

Innate immune system - 2nd line of defence

Provides non-specific resistance that attempts to destroy any invading pathogens. Adaptations; inflammation, phagocytosis, fever, cell death.

2nd line of defence - Inflammation

Small messenger proteins, called cytokines send signals from a site of injury to the bloodstream, where defence molecules and cells move to the site of injury ready for the pathogenic onslaught. This extra volume of blood causes swelling, heat and redness - symptoms of inflammation.

2nd line of defence - Fever

The cytokines signal the hypothalamus in the brain to increase the body's temperature by a couple degrees, which can then damage the enzymes in bacteria or unravel the RNA folds of a virus.

2nd line of defence - Phagocytosis

The process by which one cell engulfs another; they recognise and engulf smaller pathogenic invading cells. They have special enzymes (released from the lysosome) that help breakdown the pathogen.

2nd line of defence - Cell death

A cluster of cells may surround the pathogen and damage tissue, sealing off the pathogen from other areas of the body.

white blood cells (phagocytosis) - Neutrophils

The first to move to the site of infection to inactivate pathogens. They are short acting and then self-destruct after a few days. They are used in the body to fight acute (short, severe) infections. An increase in circulating neutrophils in the blood is indicative of an active site of inflammation in the body.

white blood cells (phagocytosis) - Monocytes

circulate in the blood until attracted to inflamed tissue. They migrate through capillary walls to the tissue, were they undergo a transformation into macrophages and dendritic cells. They are used to fight chronic infections.

Lymphatic system

A network of tissues and organs that help rid the body of toxins, waste and other unwanted materials. The primary function of the lymphatic system is to transport lymph, a fluid containing infection-fighting white blood cells, throughout the body. It consists of lymph, lymph nodes, lymph vessels, thymus, spleen, tonsils and adenoids and it plays a primary role in defending the body; swollen lymph nodes can be an indicator of infection within the body.

Specific Immunity - The 3rd Line of Defence

It is specific because the lymphocyte cells are able to identify particular pathogens by their antigens and set up defences which will accurately target each one. Cells responsible for this are the white blood cells known as "T-lymphocytes" and "B-lymphocytes" - B-lymphocytes produce proteins molecules called "antibodies" which "lock-onto" foreign antigens. Antibodies are Y-shaped proteins, also called immunoglobulins which are produced by specific lymphocytes in response to an antigen in the body. They have antigen-binding sites specifically matched for the antigen they are fighting, similar to the lock-and-key model. The antibodies then seek out the antigen and bind to a part of it, forming the antigen-antibody-complex, restricting and deactivating the antigen.

T-lymphocytes (four types)

Produced in bone marrow, but mature and multiply in the thymus gland; hence the name "t" cells. "cell-mediated" immune response. They attack body cells that are infected by pathogens

T-cells - Helpers

Interact with phagocytes to set off the specific immune response.

T-cells - Cytotoxic

(Killer T-Cells) attack the body cells which are infected by pathogens.

T-cells - Suppressor

Suppress the immune response ('turn it off') after an infection is defeated.

T-cells - Memory

Remain in the system to respond to future infection by the same pathogen.

B-lymphocytes (two types)

Produced and mature in bone marrow, they produce antibodies. "Antibody-mediated" immune response which attacks pathogens and their toxins which are not inside body cell, but in the blood, lymph or tissue fluids.

B cells - Plasma

Produce antibodies to fight the current infection.

B cells - Memory

Remain in the system to respond to future infection by the same pathogens.

Theory of Clonal selection

Sir MacFarlane Burnet was a founder of immunology. He won a nobel prize in 1960 for predicting acquired immune tolerance and developing the theory of clonal selection. The theory states that antibodies and their corresponding lymphocytes for all possible antigens are already present in very small amounts in the immune system and are cloned to fight of the particular pathogen and stores them for further attacks.

Primary exposure of a pathogen starts the initial immune response

When helper T cells are activated, it secrete a cytokine called interleukin which 1. activates clones of B cells that are specific to the antigen, making it easier for macrophages and cytotoxic T cells to attack the pathogens and 2. specific cytotoxic T cells are cloned, which kill and infect cancer cells and other damaged cells. After the infection is defeated, suppressor T cells come and suppress the activity of B and T cells back to their normal function. Memory T cells are then produced and remain in the lymph system, in case of the same pathogen attacks again while the B cells differentiate into memory B cells, which activate the immune system again if the same antigen is detected and plasma cells, which produce specific antibodies to the detected antigen.

Secondary exposure of a pathogen starts the initial immune response

After antigen presentation, helper T cells send cytokines to the lymph system, activating the memory B and T cells; the main role of innate immune response during this stage being to present antigens to help the T cells. Antibody levels peak within 2-3 days at higher plasma levels than primary response - activated B clone generate antibodies that bind with greater affinity and plasma antibody levels remain high for weeks to months after the exposure, with 100-1000 more antigens produced than during primary exposure.

There are five strategies use to ensure the pathogen is stopped...

Neutralisation; antibodies bind to and coat pathogens, blocking their activity, agglutination; neutralised pathogens clump together and surrounded by antibodies, precipitation; of dissolved antigens, activation; of the complement system, leading to lysis of infected cells, opsonisation; enhance phagocytosis by natural killer cells .

The immune response after primary exposure to bacteria

Innate immune response;
Complement proteins directly puncture the bacterial cell wall and membrane and make it susceptible to osmotic lysis, opsonised bacteria, which are coated with antibodies and complement proteins are phagocytosed, neutrophils are particularly active during bacterial infections. Peripheral blood levels of neutrophils increase in response to increased bone marrow production. This is especially common with gram- positive bacterial infections. Extreme infections may cause neutropenia due to increased demand for neutrophils outstripping the ability of the bone marrow to supply them and monocytosis may occur, particularly in the resolution phase of a bacterial infection.

Adaptive immune responses;
Intracellular: Cell-mediated immunity is launched against intracellular bacteria (such as Salmonella), which cannot be accessed by complement or antibodies. Infected macrophages present bacterial proteins on their cell surface using MHCII receptors. Helper T cells detect these and release interferon, which stimulates the macrophage to digest the bacterium-infected macrophages

Extracellular: Extracellular bacterial infections (i.e. Staphylococcus aureus) are the most frequent of all. In such cases, the protection mechanisms are mainly related to the host's natural barriers, other innate immune responses and antibody production by the adaptive immune system

Once the virus is inside the cell, the host's immune system has no access to the virus, therefore the infected cells use MHCI molecules on their cell membrane to present pieces of viral proteins to the outside of the cell.

Cytotoxic T cells recognise specific virally infected cells and only T cells with the specific T cell receptors for that particular virus are activated. The cytotoxic T cell then release cytotoxic factors that kill the virally infected cell. They also produce cytokines that prevent the replication of viruses inside the infected cell.

Natural killer cells (phagocytes) can detect if cells with fewer than normal MHCI receptors are present and release cytotoxic factors, killing them as they would a virally infected cell.

Full blood counts are unpredictable in viral infections; the white cell count may be reduced due to the suppression of bone marrow production of white blood cells.

The immune response after primary exposure to protozoa

Protozoa usually cause chronic infections, as the innate immune defence are often ineffective and the pathogen has evolved many mechanisms to resist the defence. It activates different immune responses: full blood counts usually show eosinophils, due to accelerated bone marrow production of eosinophils, some protozoa may be phagocytosed by macrophages, but many protozoa are resistant to phagocytic killing and can even replicate within macrophages and they have features known as escape/evasion mechanisms which allow the parasites to avoid the killing effects of the immune system and immunocompetent host.

The immune response after primary exposure to macroparasites

Pathogens factors pose unique challenges for the adaptive and innate immune response: many have multiple life stages (parasitic worms), many worms can infest a number of hosts as they develop, changing dramatically before moving to the next host, chronic infestation can lead to pathological changes, parasites may modulate their surface structure to avoid recognition by the host, molecular cross-talk occurs between helminths and the mammalian immune system.

Host factors: full blood counts usually show eosinophilia, Th2 cytokines such as interleukin are increased, initial increase in T cell reaction dampens as the infestation becomes chronic, memory protects the host from new infections while the old infestation continues, antiparasitic IgE levels correlate with resistance to new infestation in the host, Th2 response gene in some families help confer resistance, eosinophils kill opsonised helminths.

Herd immunity

A form of immunity that occurs when the vaccination of a significant portion of a population (herd) provides a measure of protection for individuals who have not developed immunity.

Factors involved in monitoring and control (local)

Local factors; relate to a neighbourhood, village, town or city:
Sanitation (how waste and sewage is disposed) influence transmission, overcrowding increase the chance of transmission, poor communication networks and roads, limits access to medical treatment, hospital or medical information; increase the risk of transmission, animal husbandry practices may facilitate the transmission of disease, cultural and spiritual beliefs may influence attitudes toward medical advice; influences the transmission of disease as well.

Factors involved in monitoring and control (regional)

A region is characterised by mountains, deserts, rainforests or grasslands and these geographical factors determine whether a population in that region is highly mobile or relative isolated. An example being ; Increased trade of fresh food around regional areas creates a possible source of pathogen transmission: faecal contamination of frozen mixed berries imported from China in 2016 contributed to a number of Australians testing positive for hepatitis A: region to region .

Factors involved in monitoring and control (global)

Movement of people around the globe and migration of people across countries.

Factors involved in disease transmission - pathogen factors

Some are virulent and can cause disease even in low numbers, others can only do so in large numbers, some form natural reservoirs in food, water and the environment, some are not environmentally resilient; must be transferred directly from host-host, incubation period differs for each pathogen, virulence factors (pathogen strategies).

Factors involved in disease transmission - host factors

Human immune system has a range of barriers that prevent pathogens entry, mutations affect the effectiveness of the host's ability to defend the body, certain pharmaceutical can lower the body's barrier against pathogens, illness can also decreases the body's ability to fight off pathogens.

Factors involved in disease transmission - environmental and geographical factors

Environmental conditions can favour preservation of the pathogen, some environments can predispose the spread of infectious diseases.

Factors involved in disease transmission - social factors

Anti-vaccinations, advent of mass human population movement; refugees, isolated societies with small gene pools; lack of variation in innate immunity and the absence of adaptive immunity can be devastating of small, isolated populations, international travel.

Preventing the spread of infectious disease - hygiene

Personal hygiene involves each person keeping their body and any opening on it clean to reduce the risk of pathogens entering the body. Can be done through washing your hands with soap and water, washing your body and hair regularly and cleaning your teeth, cough or sneeze into a handkerchief or tissue (or elbow).

Community hygiene: sewage and garbage disposal reduces the risk of pathogen numbers increasing and spreading within the community
Sterilisation and disinfection of equipment in hospitals, doctors' surgeries, dentists and hairdressers/barbers, as well as city planning, reduce overcrowding.

Preventing the spread of infectious disease - quarantine

Used to minimise the risk of exotic pests and diseases entering a country in order to protect the native flora and fauna, agricultural industries, local environments, health.

Preventing the spread of infectious disease - vaccination

Involves the introduction of a vaccine into the body : immunisation is the process in which the body reacts to a vaccine by going through the immune response. This response produces memory cells for the antigen and confers immunity to the body, so that if the antigen enters the body again in the future, the secondary response will occur and the person will avoid the worst symptoms of the disease.

Active acquired immunity is when the immune response occurs and memory cells are produced, which occurs after a vaccination against a certain disease.

Passive acquired immunity involves the introduction of antibodies (immunoglobulins) into the body to prevent a disease from developing.

Preventing the spread of infectious disease - public health campaigns

Broken down into four main categories: resolution of governments and health organisations to find solutions, information in the form of epidemiological studies and scientific studies of the pathogen and its mode of transmission so the solution can be accurate, coordination of efforts on a local, regional and global scale and education of human population on local regional and global scale regarding factors affecting infectious disease transmission

Ways public health campaigns prevents disease include: control and prevention of disease, implementation if public health programs i.e. immunisation programs, government regulations to ensure standardised procedures are followed, following strict guidelines and notifiable disease; certain diseases are to be reported to authorities if detected .

Preventing the spread of infectious disease - use of pesticides

Pesticides are chemical used to kill the pest of plants and animals. Can be classified into three groups; insecticides: kill insects, fungicides - kill fungal pathogens and herbicides - kill weeds.

Risk of resistance being built-up, reducing the effectiveness and chemical pesticides affect the environment negatively, therefore the use of natural pesticides is gaining popularity.

Preventing the spread of infectious disease - genetic engineering

Involves the altering of genetic composition of an organism in hopes to make them resistance to disease and prevent disease occurring (controlling the spread) . The modification of an organism's genome. Genetic sterilisation of male Aedes aegypti mosquitoes and Bt cotton are two examples of genetic engineering.

Antibiotics: antibiotics kill bacterial infections

Antibiotics can be bacteriostatic or bactericidal

Bacteriostatic = to stop bacteria growth. It slows the growth of bacteria by interfering with the process the bacteria need to multiply through processes like: DNA replication, metabolism e.g. enzyme activity and protein production. Bacteriostatic antibodies do not attack body cells and therefore do not slow the growth of viruses within the body

Bactericidal = to kill bacteria. It kill bacteria by interfering with the formation of the cell wall or cell membrane.

Antibiotics can also be so-called broad spectrum, affecting many different bacteria in the body i.e. useful bacteria in your gut or more narrow spectrum, meaning it only affects one or two types of bacteria: should use narrow spectrum antibiotics when possible.

Positives of antibiotics: over 200 million lives have been directly saved from antibiotics, more easy to target.

Negatives of antibiotics: only work on bacterial infections, misuse and overuse have led to multiple examples of antibiotic resistance, people can be allergic to antibiotics there can be side effects.

Antivirals: antiviral kill viral infections

Antivirals are a drug that kills or suppresses a virus's ability to replicate:
Inactivation of virus envelope proteins, prevention of viral attachment and entry to the host cell, prevention of viral replication, prevention of viral protein synthesis and preventing release of new infectious virus from the host cell.

Positives of antivirals: designed to target specific viral pathogens, can significantly improve the health outcomes and life expectancy.

Negatives: challenging to make safe and effective antiviral drugs, high mutation rates of viruses; drug resistance, pharmaceutical companies have a monopoly on the market, reflecting the drug cost.

Environmental management and quarantine methods used to control

Epidemic - localised; ebola
Pandemic - cross countries or countries; spanish flu

Primary principle of controlling disease spread: prevent infected individuals coming in contact with non-infected individuals.

Bush medicine (examples)

Tea tree oil (melaleuca alternifolia) - used to create a paste that contains the oil and as an antiseptic to treat wounds and infections.

Eucalyptus oil (Eucalyptus sp.) - indigenous have used the oils for their natural antimicrobial and antiseptic properties; now used commercially in mouthwash, throat lozenges and cough suppressants.

Kakadu plum (Terminalia ferdinandiana) - the world's richest source of vitamin C.

Emu bush (Eremophila glabra) - some people used to leaves to make an antiseptic solution that treat wounds; now being proposed to use the plant to sterilise artificial joints.

Kangaroo apple (Solanum laciniatum and Solanum aviculare) - Aboriginals apply pulp of the fruit on swollen joints to reduce swelling and inflammation.

Smoke Bush (Conospermum stoechadis) in WA

It has been used by Aboriginals for thousands of years for its healing properties. In the late 1980's, the WA government had legislative power to grant licensing rights to commercial deals to pharmaceutical companies; at the time of issuing the license, the WA government has not acknowledged or included any Abogrinal people of WA in any royalties or compensation agreements.

Considerations: Aboriginals have used smoked bush for thousands of years for its healing properties and passed on this knowledge from generation to generation. Government agencies and pharmaceutical companies have invested significant time and millions of dollars in researching smoke bush.

Introduction to disease control

Chines and hebrew were the first to advocate cleanliness in food, water and personal hygiene; Chinese deduced a connection between water contaminated by feces and gastro-intestinal disease were Hebrews are believed to have made the connection between the symptoms of infection by tapeworm and eating undercooked pork.

Cholera

Infectious disease of the intestines caused by the bacterium vibrio cholerae. In the past two hundred years, their have been seven pandemics
WHO suggests there are up to 5 million new cases and 100,000 deaths annually caused by cholera. Modern day sewage and water treatment systems have largely eliminated cholera from developed countries, but it is still a major concern in third world countries, where there is limited access to clean drinking water.

Evaluation of disease spread strategies: germ theory (Pastuer and Koch); most significant breakthrough in the effective control of infectious diseases allowing for specific preventive and control measures to be taken into place to avoid infection.

Dengue fever

A mosquito-borne viral infection found in tropical and sub-tropical climate worldwide, causes flu-like symptoms and be potentially lethal (severe dengue). Half of the world's population is now at risk of contracting dengue fever. 390 millions new infections per year, 250,000 deaths annually worldwide; America, southeast Asia and western pascific are more seriously affected.

Malaria

Caused by four protozoan parasitic species of the genus plasmodium; plasmodium falciparum, plasmodium vivax, plasmodium ovale and plasmodium malariae.

Single-celled organisms that cannot survive outside their host. Has a life cycle in both humans and the female anopheles (parasite)

Changes several life stages, each preventing the host from launching an effective immune response. In the red blood cells, adhesion proteins are produced by changing the shape of the cells and interfering with their movement. This change is alerted before the human immune system can effectively respond. In the liver, they can kill the cell causing them to spread to surrounding cells but also accumulate calcium ions from the lover cell to use as a blocker against antigens. The saliva of the female anopheles mosquito contains an anticoagulant protein, inhibiting clotting.

HIV

It has a high replication rate and antigen proteins on the surface of the virus mutate rapidly to avoid the immune system. It is covered with glycans, which also helps avoid detection and it can block interferon signaling between the B and T lymphocytes.

Ebola

Ebola virus disease (EVD) is a server, fatal disease in humans
Fruit bats are the natural host of EVD and is initially transmitted to humans from an infected animal and continues to spread through direct human-to-human contact.

Factors that affect transmission: virulence of the virus strain, population density, population mobility in infected area, host exposure and susceptibility, cultural beliefs and behaviour practices, public health infrastructure.

EVD initially infects the cells of the dendritic cells of the immune system, preventing an immune response. It then replicates on mass and infects the cells of multiple organs resulting in cell death. This leads to the release of cytokines, which thins the blood vessel walls causing them to leak blood. Blood pressure drops significantly as well as body temperature, causing the infected person to go into shock and die.

Incubation period: 2 to 21 days

Initial symptoms: fever, fatigue, muscle pain, headache and sore throat
Severe symptoms: vomiting, diarrhoea, rash, impaired kidney and liver function, internal and external bleeding

Can persist for more than 9 months after recovery in the testicles, eyes, CNS and placenta and milk of pregnant women

Prevent and control: avoid human-to-human transmission through wearing personal protective equipment, ensure good personal hygiene and refrain from unprotected sex.

Avoid animal-to-human transmission by cooking meat thoroughly, surveillance of known hot spots, contact tracing laboratory testing and safe burials, social mobilisation and quarantine.