infectious diseases

Microbe

A micro-scopic organsim

Spontaneous Generation Theory

The theory Louis Pasteur disproved

Germ Theory

Theory that Louis Pasteur developed

Cell-wall degrading toxins

Breaks plant cell wall down, intracellular nutrients spill out

Toxins

Pathogen-produced molecule that promotes infection

Effector protein

Secreted in/around host cell, suppress host defences

Extremophiles (Archaea)

Pathogens that survive in extreme conditions (outside of host)

Or lovers of extreme conditions
{extremo} {phile}

Reservoirs

Sites (biotic and abiotic) where multitude of pathogens live

Vector

Living organism that carries, develops and transmits disease e.g. mosquito & malaria

direct contact transmission

physical contact between infected/susceptible hosts

indirect contact transmission

situations in which a susceptible person is infected by contact with a contaminated surface or substance

Bacterial Capsules

Protective covering, impedes phagocytosis, may enhance adherence to tissues

viral envelope

Protective layer around virus, composed of protein/lipids, protects against host defences

Rapid species evolution

Rapid rates of mutation in pathogen genomes lead to quicker pathogen evolution

System Acquired Resistance

A defensive response in infected plants that helps protect healthy tissue from pathogenic invasion.

Singal transduction pathway

Where a cell converts an extra-cellular signal into a response

Hypersensitive response (HR)

The killing of necrosed plant tissue, releasing antimicrobial molecules as the infected cells die

Salicylic acid

An antimicrobial substance that induces STP, which provides healthy plant cells with a defence against pathogens.

Mucous membrane (7.2)

Cells that line the openings of the body (e.g. respiratory tract)

Cilia

Hair-like projections, line air passages and push pathogens away from lungs in wave like motions

Lymph system

This system is part of the circulatory system. It produces lymphocytes to fight infection that may be found in the blood stream. It also collects, filters (lymph nodes), and transports fluids from around the tissues back to the veins of the circulatory system.


Includes lymphatic vessels, spleen, lymph nodes and thymus

Inflammation

a localized physical condition in which part of the body becomes reddened, swollen, hot, and often painful with increased blood flow, meaning additional WBCs to assist with infection.

Histamine

A chemical involved in inflammation

Antigen

a toxin or other foreign substance that induces an immune response in the body, especially the production of antibodies.

Phagocytosis

Ingestion of pathogen/foreign cells or particles

Macrophage

Phagocytic, white blood cell that locates and engulfs pathogens

Phagosomes

Phagosomes A vesicle formed around an engulfed particle via phagocytosis

Apoptosis

Programmed cell death. Macrophages and lymphocytes surround cell and trigger this process via cytotoxins. This forms a cyst, which immobilizes the pathogen and stops the flow of nutrients.

Lymphocyte

A small white blood cell in the lymphatic system, branch into specialty cells for the immune system

Innate Immune system

Non specialised response, rapid response rate (1st & 2nd line)

Adaptive Immune system

Specialised protection, immunological memory, longer response rate.

B cells/lymphocytes

Mature in the bone marrow
Produce antibodies
Differentiate into plasma (secrete antibodies of same specificity) and memory (store immunological record of certain pathogen, stay in circulation) cells once activated by pathogen

B cells/lymphocytes

Mature in the bone marrow
Produce antibodies
Differentiate into plasma (secrete antibodies of same specificity) and memory (store immunological record of certain pathogen, stay in circulation) cells once activated by pathogen

Helper T cells

Assist various wbcs in their immunological processes
Rapidly divide and secrete cytokines once selected by an antigen

Cytokines

Signaling molecules that coordinate immune responses

Cytotoxic T cells (killers)

Send signals to infected cells to destroy itself by releasing cytotoxins, which trigger apoptosis

Regulatory T cells

Suppress immune response once pathogen has been destroyed/infection has gone away; have receptor molecule CD8 on their surface; together with killer T cells they are called the T8 cells

Memory T cells

Provide immunological memory of specific pathogen and remain in circulation, to provide stronger response upon secondary infection

(remember antibody concentration over time
graph?)

Neutralisation

Antibodies bind to important molecules expressed by the pathogen to block their effect on host cell

Opsonisation

Antibodies binding to surface antigens on pathogens improves the efficiency of phagocytosis

Complement system

By binding to pathogens in the bloodstream, the antibodies activate lysis and ingestion.

Clonal selection

Adaptive immune system gaining specificity against pathogens. Goes through:
Variation, selection pressures and reproduction

Incidence

Amount of new cases within a defined population over an established period of time

Prevalence

Number of active cases at any given time

Endemic

confined to a particular country or area

Epidemic

A localised outbreak of an infectious disease. across a large area e.g. Ebola

Pandemic

worldwide spread of the disease

Genetic Engineering

A technology that includes the process of manipulating or altering the genetic material of a cell resulting in desirable functions or outcomes that would not occur naturally. e.g. deleting the malaria gene in anopheles mosquitoes.

Antivirals

inhibit development of specific viruses

Antibiotics

Drugs that block the growth and reproduction of bacteria

Name the different types of antivirals

before cell entry
during viral synthesis
inhibition of reverse transcription
inhibition of transcription
inhibition of protease activity
release phase

Name the different types of antibiotics

interference with cell membrane permeability
interference with nucleic acid synthesis
interference with protein synthesis
interference with cell wall synthesis

antibiotic resistance

the evolution of populations of pathogenic bacteria that antibiotics are unable to kill

Antiviral resistance

Ability of a virus to overcome the suppressive action of antiviral agents

Incidence

frequency of a particular population affected by a disease

Prevalence

proportion of a particular population affected

morbidity rates

amount of deaths in within certain population as a result of disease

Historical example of prediction and control
1377 CE

City of Marseille, quarantine implemented for the plague. Individuals who had travelled from affected areas isolated for 40 days

Historical example of prediction and control
1849 CE

Dr John Snow maps cases of cholera on a map and locates clusters around water source, realises its a water borne disease

Historical example of prediction and control
1965 CE

Director General of WHO implements surveillance to globally track the spread of communicable diseases

Current strategies for prediction
Event-Based Surveillance

GPHIN scans informal sources for unusual disease events or outbreak rumours, effective for countries with poor public health facilities. e.g. 2002 SARS outbreak

Current strategies for prediction
web-based surveillance

Google Flu Trends predicts 1-2 weeks earlier

Bush Medicine

skills and practice used to maintain health, based on Indigenous experiences and beliefs, weaves all dimensions of life

Tea Tree Oil
Indigenous and Western uses

Indigenous:
- crushed leaves applied as paste to wounds
- brewed into tea for throat ailments
Western:
bacterial and acne treatment

Eucalytpus Oil
Indigenous and Western uses

Indigenous:
-Infusions treat muscle aches, chills and fevers
Western:
mouthwash and cough lollies

Mudjala Plant Patent

1960's US Cancer Institute found cancer fighting molecules in the plant
found to be ineffective

interleukins

proteins (cytokines) that stimulate the growth of B and T lymphocytes

intereferons

-produced by cells infected with viruses
-trigger a series of cell responses to inhibit viral replication and activate cytotoxic t cells and natural killer cells

defensins

-antimicrobial peptides that inhibit microbial growth
-they signal the body to initiate, mobilise and amplify adaptive immune response
-produced by epithelial lining of the gut, phagocytic cells and lymphocytes

Immunoglobulin M

the first immunoglobulin the body produces when challenged by an antigen and is found in circulating fluids; makes infected cells clump together

Immunoglobulin G

the most abundant class of antibodies; found in blood serum and lymph; active against bacteria, fungi, viruses, and foreign particles; activate the complement system and marks pathogens by attaching to them, making them palatable

theory of clonal selection

Explains the generation of primary and secondary immune responses. The binding of a B cell to an antigen stimulates the cell to divide, giving rise to a clone of genetically identical cells, all of which are specific for the antigen.

What happens in the secondary response?

-shorter lag period between encounter with Ag and appearance of Abs
-Ab production is higher and more persistent
-higher Ab titres at peak of response
-Abs with a higher affinity for Ag than those produced in primary response

What is the response when an antigen enters again, and what happens to the body?

the immune system does not return to pre-immune status. It remains primed, as though the Ag is remembered to give an enhanced secondary response.
This is called the memory or anamnestic response

What happens if a pathogen is too large?

a group of macrophages and neutrophils will gather around the invader
Secretes defensins and toxins to destroy the pathogen

Examples of non-specific innate barriers

-protective barriers on outside of skin
-protective barriers on membranes
-bacteria-killing substances
-scavenger cells
-complement system
-natural killer cells

Factors that challenge effectiveness of antivirals and antibiotics

-lead to emergence and evolution of new infectious diseases
-may be unregulated access to and inappropriate use
-ethical issues include; high cost, mistrust
-side effects
-production can take a long time and can be expensive

herd immunity

The resistance of a group to an attack by a disease to which a large proportion of the members of the group are immune - measles 95%

IgG antibodies

the most prevalent in serum; provide naturally acquired passive immunity; neutralize bacterial toxins, participate in complement fixation and enhance phagocytosis - passed on from the mother to unborn child which protects them until immune system matures

IgA antibodies

causes phagocytosis by WBCs and prevent pathogens from adhering to mucous membranes - pass from mothers breast milk which helps prevent entry of pathogens

active immunity

A form of acquired immunity in which the body produces its own antibodies against disease-causing antigens.

passive immunity

An individual does not produce his or her own antibodies, but rather receives them directly from another source, such as mother to infant through breast milk

opsonisation

a process in which a pathogen is coated with antibodies and/or complement and marked for phagocytosis

agglutination

Clumping of microorganisms or blood cells, typically due to an antigen-antibody interaction.

granzymes and perforin

induce apoptosis

which is better to fight viruses? B or T cells and why?

T cells because they can recognise and kill cells that have been invaded by viruses, whereas B cells respond to extracellular antigens

Eucalyptus grandis + Austropuccinia psidii \= Mrytle Rust

contains specific proteins that recognise the pathogen.
has a gene that codes to produce a chitinase chemical. Once the pathogen A. psidii is recognised, the chitinase is produced by the cell. This breaks the bonds of the chitin, which is the main structural component of the fungal cell wall.

gene-for-gene resistance

In plants, a mechanism of resistance to pathogens in which resistance is triggered by the specific interaction of the products of a pathogen's Avr genes and a plant's R genes.

basal resistance

A receptor protein in the plant cell's plasma membrane binds with a pathogen-derived molecule and triggers a defense response.

phytopthora cinnamomi

fungal pathogen which causes damage to all parts of the plant

Eucalyptus defence

produces and stores oil in sub-dermal secretory glands that have anti-microbial properties

prion

Defective form of protein molecule; does not contain DNA or RNA; mostly attacks brain or nerve cell Abnormal proteins that form amyloid fibres. Replicate by transforming normal proteins.

kuru

virus

Non-cellular; contains DNA, RNA and protein coat; requires a living host cell to replicate
20-40nm
Influenza virus

protozoan

Eukaryotic cell; may have a complex life cycle; microscopic
1-150 micrometres
Plasmodium (malaria)

fungi

Eukaryotic cell with cell wall; spreads via spores or rapid division; some infect external skin and nails, while others enter the host's body
Candida albicans (Vaginal thrush)

macroparasites

Eukaryotic cell with cell wall; spreads via spores or rapid division; some infect external skin and nails, while others enter the hosts body

bacteria

Prokaryotic cell; divides quickly and/or produces toxins; various shapes
0.5-5 micrometres
Mycobacterium tuberculosis (tuberculosis)

factors limiting effectiveness of antibiotic and antivirals

·side effects - wipe out friendly bacteria along with harmful ones and this change the body's ecosystem can allow once-friendly bacteria from elsewhere in the body to colonise and become pathogenic, lead to the emergence and evolution of new infectious diseases, unregulated access to and inappropriate use of pharmaceuticals in the global marketnumber of ethical issues;

Proximity/Isolation

More isolated regions have reduced risk from pandemics due to reduced migration and travel

Population density

Regions with high population density have increased risk of disease spread due to close proximity of large numbers of people