Spread of pathogens flashcards
life cycle of a pathogen
invade the host (have a portal of entry)
exploit a nutrient-rich area of the host
avoid host defence mechanisms
replicate
exit (have a portal of exit) and transmit to new hosts (mode of transmission)
what are the portals of entry
mucous membranes
skin
wounds
eyes
ears
wounds in epidermal layers of plants and animals
skin (bite, blood feed, penetration)
what are mucous membranes
surface membranes moistened with slimy, stick and viscous mucus, lined with epithelial cells that secrete mucus. found in respiratory, gastrointestinal, and reproductive tracts.
portals of exit
bite/blood feed/salvia
digestion (elimination)
respiratory system (coughing, sneezing)
blood contact
reproductive system
what does a pathogen’s life cycle depend on?
the pathogen life cycle is dependent on having portals of entry and exit to and from a susceptible host, the ability to replicate, and modes of transmission.
what is direct transmission
is the transfer of a pathogen from an infected host, or other reservoir, to a susceptible host bydirect contacrt or close contact
what is indirect transmission
is the transfer of a pathogen from a reservoir to a host through vectors (inanimate vehicles or living intermediaries) or suspended air particles.
what is direct transmission direct contact
transmission due to physical touch between an infected host and a susceptible host via skin or body fluids
what is direct transmission close contact
transmission of pathogen in airbourne droplets between an infected host nad a suscelptible host, such as sneezing/coughing with 1.5 metres or due to close proximity
what is direct transmission reservoir?
transmission from an inanimate reservoir/fomite to a susceptible host. a reservoir could be soil, as for tetanus bacteria.
what is indirect transmission vector
a living thing that transmits a pathogen from an infected host to a susceptible host.
what is indirect transmission airbournes droplets air/fomites
pathogens can be transmitted inside airbourne droplets (aerosols) that are sneezed or coughed into air and are suspended for a period of time beofre being inhaled. they may land on surfaces and be transferred by a fomite.
what is indirect transmission soilborne/waterborne
an inanimate object acts as an intermediary between the portal of exit from the reservoir and the portnat or entry to the host. e.g. car tyres and human shoes carrying pathogens from a contaminated area to an aea containing susceptible hosts. pathogens can swim or be carried throuh water or wet soil fro an infected host to a susceptible host.
why do centries-old threats, such as influenza, malaria, and tuberculosis pose such as threat?
through a combination of mutation, rising resistance to antimicrobial medicines, globalisation, urbanisation, climate change and poor health systems.
what is disease spread?
spread is the transmission of a pathogen to a susceptible hosts over a wide area and into new populations.
what is the spread of a disease affected by?
a range of interrelated factors (factors that depend on and have an effect on one another), including growth of the pathogen population, density of the host population and modes of transmission.
why do the three factors of disease spread have a big impact?
they play an important part in spread, all three factors need to reach particular thresholds or spread will be limited.
what is a threshold?
control of any disease is related to thresholds. a threshold is a certain magnitude that must be exceeded before a result can be produced. certain parameters or host/pathogen/vector population sizes must be exceeded for a specific infectious disease to spread.
impact of the pathogen population on the spread of a disease
an increase in the growth of a pathogen pop. can lead to increase in spread of disease. greater abundance of a pathogen means risk of transmission is higher. keep in mind spread relies on all three factors, so if one is lacking, there will be a limiting factor in a pathogens spread.
impact of the density of the host population on the spread of a disease.
a higher population density means that more people are in particular area at the same time. more susceptible individuals will come into contact with infected individuals .
impact of the mode of transmission on spread of a disease
MOT can change due to environmental conditions. even though a pathogen may be spread via several modes of transmission, they still relies on a threshold number of pathogens being present and a certain level of host population density to successfully spread.
what factors increase host susceptibility?
high population density
poor living conditions
lack of adequate healthcare provisions
what are the three categories of emerging diseases?
disease that have recently appeared in a population
diseases that have occurred previously but until recently have affected only small numbers in isolated places
disease that have occurred previously but only recently have been associated with a newly identified pathogen.
what factors of a pathogen are targeted in the spread and control of a disease
the mechanism of transmission
environmental factors (such as climate)
characteristics of the infected population (such as levels of immunisation)
what is disease management
disease management is a coordinated response involving prevention, control and treatment, and is a response that is specific for each infectious disease.
what does prevention include
the prevention of the transmission of a disease, of the onset of disease signs and symptoms, and of the impact of the disease on the environment or society.
practices that prevent spread of disease.
practices that prevent spread of disease include hygiene practices quarantine, vaccination, public health campaigns use of pesticides, and genetic engineering.
how does understanding the life cycle of a pathogen help to prevent and control disease
list the criteria for someone to be identified as ‘cured’ of an infectious disease.
managemetn stratergies that prevent the spread of pathogens
immunisation, quarantine, disruption of pathogen life cycles, medications (antibiotics and antivirals) and physical preventative measures.
a set of statergies that support the prevention of, response to and recovery from diseases that affect our economy, environment and health.
a period of isolation to prevent the spread of a contagious disease
practices that prevent spread of disease.
list five potential carriers of disease inspected by biosecurity officers in australia
what is herd immunity
when high enough proportion of a population , the threshold population, is immune to an infectious disease, the fraction who are not immune are to a large degree protected from transmission.¸ÅSq1
what does herd immunity do specifically?
herd immunity can stop a disease from spreading, and it prevents outbreaks. when a high threshold percentage of the population is vaccinated, it is difficult for infectious diseases that are contagious to spread because there are not many people who can be infected.
Give an example of both natural and artifical active immunity
natural = infection
vaccination = artificial
give an example of both natural and artificial passive immunity
natural = maternal antibodies
artificial = monoclonal antibodies
downside of herd immunity
herd immunity does not protect against all vaccine-preventable diseases, such as tetanus which is infectious but not contagious.
why does herd immunity work?
there will be too few susceptible hosts for pathogen to be transmitted to. lack of susceptible host provides protection to the vulnerable people in a community, such as people with a compromised immune system. if a certain threshold of people have been immunised, then the few who have not had a low chance of becoming infected.
what are the first 1-2 principles of herd immunity
- critical (high enough) proportion of the host population becomes immune to a specific disease.
- immunity is usually by an artificial vaccine (or can be gained naturally by recovery from disease) causing the formation of specific antibodies and memory cells against a specific pathogen.
what the 3-4 principles of herd immunity
- this limits the spread of the disease, because there are too few susceptible people to sustain the spread. the pathogen cannot reproduce at a highh enough rate to sustain its population.
- infected hoats carrying the pathogen are more likely to come into contact with immune individuals, reducing the possibility of transmission and reducing the risk of susceptible people.
what the 5-6 principles of herd immunity
- the higher the proportion of immune individuals, the greater the protection
- it protects people who cannot be vaccinated, such as people with an anaphylactic reaction to a vaccine ingredient, and pregnant women or those undergoing a treatment that suppresses their immune system.
what is the 7th principle of herd immunity
the proportion of the population who need to be immune to create herd immunity depends on the virulence and infectivity of the pathogen.
what three factors are nedded for disease spread
- a susceptible host is sufficient density
- growth of a virulent pathogen population
- transmission
what are the modes of antibiotic action
inhibition of protein synthesis
inhibition of nucleic acid synthesis
inhibition of cell wall synthesis
disruption of cell membrane function
blocking pathways and inhibiting metabolism
what are the modes of antiviral action
inhibit binding or attachment (known as ‘entry blocking’ drugs_
inhibiting entry or penetration by blocking protein channels in the host cell membrane
inhibit transcription of the virus by blocking transcription factors to viral DNA
prevent the release of the newly assembled viruses from the cell membrane
two differences between antibiotics and antivirals
explain why certain structures on a bacterium have been chosen as targets for the action of antibiotics. give two examples of these.
medications (e.g. antibiotic and antiviral) and physical preventative measures (e.g. hand-washing, filtered water, sanitation, sneezing into your elbow and barriers) help to prevent and control the spread of disease.
describe two different types of physical barrier that prevent the spread of disease
describe two methods of removing or killing pathogens
what does the life cycle specifications entail?
portal of entry, site of replication (sexual/asexual reproduction), reservoir, portal of exit.
define Endemic diseases
Common in population but at low level
define outbreak
Sudden increase in incidence
define Infectious Diseases
Caused by an agent that can be passed from one organism to another
Infected organism host
Infectious organism pathogen
Eg. Viruses, bacteria, fungi, protists
define Transmission
Passing of disease from infected host to other individual
Pathogens have variety of adaptations for transmission
Easily transmitted diseases
Contagious
Non-Infectious Diseases
Not caused by pathogens
Not communicable / transmittable
Eg. Nutritional or degenerative diseases
Autoimmune Diseases
When tissues are attacked by body’s own immune system
Eg. Multiple sclerosis
Genetic Diseases
Due to mutations inherited by parents
Eg. Cystic fibrosis
Nature of Disease
Most microorganisms are not pathogens
Can be pathogenic due to certain features, eg.
Can stick to / invade cell
Produces toxins
Copes with / avoids immune system
Variations in Pathogens
Vary in pathogenicity
Vary in virulence
define pathogenicity
Disease causing capacity
define virulence
Intensity of their effect
Variations in Individuals
Vary in susceptibility
Some have greater resistance
Depends on age, state of health, natural resistance etc.
Symptoms
The effect the pathogen has on the body of its host
Diseases usually have characteristic symptoms
Helps in diagnosis
Incubation Periods
Sometimes symptoms do not appear immediately
Incubation period
Time between infection + onset of symptoms
Diseases often contagious before onset of symptoms
Dangerous
Incubation may be adaptation of pathogen to increase transmission
why do incubation periods exist
Pathogen may need to divide
May take time to reach target tissue
Toxins may take time to accumulate
list some modes of transmission
Direct contact
Bodily fluids
Foodbourne
Airbourne
Waterbourne
Vectors
