Download Revised Higher Human FH2N 12 Immunology and Public Health

CfE Higher Human Biology
Section 2 of Unit 4
Infectious Diseases & Immunity
Learning Objective
2.1 Infectious Diseases and Immunity
2.2 Infectious Diseases and Immunity
– Transmission
Classification of microbes
Giardia
Algae
Fungi
TrichophytonATHLETES FOOT
Bacteria
E.coli
Protozoa
Viruses
Cold /flu
Pathogens and disease
An infectious disease is a
disease resulting from infection
of a host organism by a
pathogen, a disease-causing
organism.
There are several different types
of pathogen including bacteria,
fungi, viruses and parasites.
Infectious disease is a major
cause of death worldwide.
It is estimated that 14.7
million people died in 2002
due to infectious diseases.
Trichophyton-ATHLETES FOOT
Cause- fungal growth on surface of skin
Symptoms-Dry flaking skin on the soles of
the feet. Unpleasant foot odour. Small itchy
bubbles or blisters on the soles of the feet.
Transmission- Athlete's foot is mildly
contagious. It can be spread through
direct contact with the infection and by
skin particles left on towels, shoes,
floors of shower cubicles and changing
rooms, and around pools.
Treatment- Most cases of athlete's foot can
be cured with over-the-counter antifungal
products and basic good hygiene.
E.coli
Cause- most strains are harmless and are
found in the intestines of most animals. The
strain E. coli 0157 is harmful.
Symptoms- cramping vomiting, diarrhoea,
fever dehydration
Transmission- eating undercooked meat or
consumes unpasteurised milk or cheese.
Having contact with infected animals, such
as on farms and at children's petting zoos.
Contact with other people who have the
illness, through inadequate hand-washing
after using the toilet and before handling or
eating food.
Eating unwashed vegetables which have
come into contact with manure from
infected cattle.
Drinking or swimming in infected water.
Treatment- Drink plenty of fluids
Influenza
Cause- viral infection
Symptoms- It usually causes
aching muscles and joints,
headaches fevers and coughs. Can
lead to pneumonia, nerve and
brain damage and even death
Transmission- person to
person through the air
Treatment- rest sleep plenty of
fluids antiviral drugs,
vaccination
How easily can a disease be
transmitted by hand to hand
contact?
Activity
Transmission
 The main ways a disease can spread from
person to person are: 1. Air - when someone coughs or sneezes,
a spray of tiny watery droplets enters the
air. These may contain microbes.
 If someone else breathes in the droplets
they may become infected with the
microbes and get a disease
 Colds, flu, measles, chickenpox and TB are
all spread in this way
How virus attacks body

Transmission
 2. Touch – some diseases are passed on by
touching an infected person
 Athlete’s foot can be spread by touch or
indirectly, by treading barefoot on a wet floor
where an infected person has recently trodden
 MRSA can be spread from person to person by
touch or by contact with sheets, clothing or
equipment
Transmission
Transmission
 3. Water – in overcrowded conditions, people’s
sewage can get into the drinking water
 Cholera can spread in this way
 Why do you think cholera often occurs in areas
hit by wars or natural disasters?
Transmission
4. Food – food poisoning is caused by
bacteria in food
Animals learn to avoid eating certain foods
that make them ill
Humans have learned to cook – which
should thoroughly kill bacteria
Transmission
5. Vectors – Some microbes are carried by
animals
E.g. mosquitoes carry the microbe that
cause malaria & yellow fever
E.g. mosquitoes carry the microbe that
cause malaria & yellow fever

Transmission
Direct physical contact
Water
Food
Body fluids
Inhaled air
Vector organisms.
Vector
 Vectors organisms provide a pathway for a
pathogen to be transmitted between animals and
humans or other animals.
 Some vector organisms provide this transport by
the means of blood-sucking.
 Malaria caused by the protozoa Plasmodium
spread by mosquitoes
 Dengue Fever (DF) is a virus-caused disease also
spread by mosquitoes.
Control
 Quarantine
 Antisepsis (prevent disease infection through
inhibition or arresting the areas of growth of the
infection).
 Individual responsibility (good hygiene, care in
sexual health and appropriate storage/handling
of food),
 Community responsibility (quality water supply,
safe food webs and appropriate waste disposal
systems)
 Control of vectors
Success Criteria
 Due to its role in maintaining health and combating
infectious diseases on a global level, the immune system
is at the centre of much of the research in public health.
 Infectious diseases are caused by pathogens such as
viruses, bacteria, fungi, protozoa and multicellular
parasites.
 Infectious diseases are transmitted by direct physical
contact, water, food, body fluids, inhaled air or vector
organisms.
 The transmission of infectious disease can be controlled
by quarantine, antisepsis, individual responsibility (good
hygiene, care in sexual health and appropriate
storage/handling of food), community responsibility
(quality water supply, safe food webs and appropriate
waste disposal systems) and the control of vectors.
Learning Objective
2.3 Infectious Diseases and Immunity
– Epidemiology
Epidemiologists
the outbreak and pattern of infectious
diseases to determine the factors which
affect the spread of infectious disease
Outbreaks of disease can occur on different levels:
 sporadic – (occasional occurrence) the disease
occurring occasionally, singly or in scattered
instances.
 endemic – (regular cases occurring in an area) it
is continually present in a population but at a low
level (for example the common cold).
 epidemic – (unusually high number of cases in an
area )it has suddenly increased above the normal
endemic level and infects many people.
 pandemic – (a global epidemic ) it is epidemic
over a very wide area (usually a continent or the
world).
Depending on epidemiological studies, measures are considered to
control the spread of diseases.
preventing transmission
drug therapy
immunisation
Success Criteria
 Epidemiologists study the outbreak and pattern
of infectious diseases to determine the factors
which affect the spread of infectious disease.
 The spread of infectious diseases are classified
as: sporadic (occasional occurrence), endemic
(regular cases occurring in an area), epidemic
(unusually high number of cases in an area) or
pandemic (a global epidemic).
 Based on epidemiological studies control
measures can be considered that include
preventing transmission, drug therapy,
immunisation or a combination of these.
Learning Objective
2.4 Infectious Diseases and Immunity
– Active Immunisation and
Vaccination
Types of Immunity - note
Active immunity- antibodies made by individual
in two ways
Natural Acquired Active – Antibodies made by
individual in response to antigen
Artificially Acquired - In response to vaccine.
Two Kinds of Passive immunity- Antibodies
given to individual
Natural - Ingested with milk shortly after birth
Acquired – injection of antibodies to combat a
disease e.g. rabies
Active immunity
Antigens usually mixed with an adjuvant to
form the active vaccine and enhance the
immune response
Vaccines include
inactivated pathogen toxins
dead pathogens
parts of pathogens
weakened pathogens.
Antibody responses
Memory Cells – lymphocytes specific to antigen from
first exposure to it.
The immune system can also be activated
artificially by the use of vaccines
Who is Edward Jenner?
Edward Jenner
Smallpox
Edward Jenner & the Small Pox Vaccine
 Use this website:
 http://www.jenner.ac.uk/edwardjenner to find
out about how Edward Jenner developed the
Small Pox Vaccine.
 Write a short note including:
 When he did this work
 How he linked cowpox and smallpox
 How he tested the vaccine
 When smallpox was eradicated
The Independent - Thursday 22 May 2014
 The General Assembly of the WHO will take a
vote on Friday (23rd May) on whether to
eradicate the variola virus completely and
forever by ordering the incineration of stockpiles
in Russia and the United States, which are kept
under an agreement signed in 1983 when Ronald
Reagan was US President and the Soviet Union
was still a country.
 http://www.independent.co.uk/news/science/h
ealth-experts-to-vote-on-whether-to-destroythe-last-few-samples-of-smallpox-9412451.html
Any further news?
Google smallpox to find out!
Success Criteria
Antigens from infectious pathogens,
usually mixed with an adjuvant to form
the active vaccine and enhance the
immune response, include inactivated
pathogen toxins, dead pathogens, parts of
pathogens and weakened pathogens.
These agents induce a primary immune
response and immunological memory in
the individual but not disease symptoms.
Learning Objective
2.5 Vaccine Clinical Trials
Few people
Larger number
Double blind procedure,
placebo
Long term effects
Success Criteria
 Vaccines are subjected to clinical trials in the
same way as other pharmaceutical medicines to
establish their safety and efficacy before being
licensed for use.
 Clinical trials use randomised, double-blind,
placebo-controlled protocols. Subjects are split
into groups in a randomised way in which
neither the subjects nor the researchers know
which group they are in to eliminate bias.
 One group of subjects receives the vaccine, while
the second group receives a placebo control to
ensure valid comparisons.
Learning Objective
2.6 Herd Immunity
2.7 Public Health Medicine
The herd immunity
threshold depends on:
1.The disease.
2.The efficacy
(effectiveness) of the
vaccine.
3.The contact
parameters for the
population.
Pros
protects vulnerable
and the nonvaccinated
Difficulties
The developing worldvaccination is not
possible due to
malnutrition and
poverty
reducing the spread of The developed worlddiseases
vaccines are rejected
by a percentage of the
population.
The MMR controversy
In 1998, a scientific paper was published in the medical journal The Lancet,
speculating that the MMR vaccine could cause autism.
The authors thought that the MMR vaccine could damage the bowel, allowing
toxins that are normally destroyed in digestion to move into the blood. If these
toxins travelled to the brain they might cause autism.
The authors did not prove that this was
the case but still recommended that
doctors stop administering the MMR
vaccine until more research was done.
The media’s role in the MMR controversy
Many studies have concluded that the MMR vaccine is safe and only a few
studies claim that it isn’t. However, this was not reflected by the media coverage.
The majority of coverage centred on the possibility of
a link between the MMR vaccine and autism, while the government insisted that
the vaccine was safe.
This mixed message caused confusion among the general public, leading to a drop
in the number of children being given the combined vaccine.
Should scientists be more careful about how they present their research or
should the media be responsible for how they present controversial topics to
society?
Evaluating scientific papers
Success Criteria
 If a large percentage of a population are immunised, nonimmune individuals are protected as there is a lower probability
that they will come into contact with infected individuals.
 This herd immunity is important in reducing the spread of
diseases and in protecting vulnerable and the non-vaccinated
 The herd immunity threshold depends on the disease, the
efficacy of the vaccine and the contact parameters for the
population.
 In most countries, policy in public health medicine is to establish
herd immunity to a number of diseases.
 Difficulties can arise when widespread vaccination is not
possible due to malnutrition and poverty (the developing world),
or when vaccines are rejected by a percentage of the population
(the developed world).
Learning Objective
2.8 Evasion of specific immune
responses by pathogens
2.9 Antigenic Variation
Many pathogens like viruses, bacteria and
protozoa can evolve mechanisms that
evade the specific immune system of the
human body and can affect vaccination
strategies globally.
Antigenic variation is a process by which a
pathogen is able to change its surface
proteins so that it can evade the host
immune responses.
 The antigenic profile will change as the pathogen passes
through the host population or in the original infected
host.
 Antigenic variation is particularly important for
pathogens as it allows them to:
 target hosts which are long-lived or susceptible to the
pathogen
 infect a single host on more than one occasion
 transmit the disease easily
This drift results in small antigenic changes in the pathogen
population and will reduce the efficacy of B and T
cell memory during the host immune response.
Success Criteria
 Many pathogens have evolved mechanisms that evade the
specific immune system which has consequences for
vaccination strategies.
 Some pathogens can change their antigens avoiding the effect
of immunological memory.
 Antigenic variation occurs in diseases like malaria and
trypanosomiasis and is one of the reasons why they are still
so common in many parts of the world.
 Antigenic variation also occurs in the influenza virus
explaining why it remains a major public health problem and
why at risk individuals require to be vaccinated every year.
Learning Objective
2.10 Direct attack on the immune
system
HIV
HIV attacks lymphocytes and is
the major cause of acquired
immunodeficiency in adults
TB
 Tuberculosis (TB)
survives within
phagocytes and
avoids immune
detection.
Success Criteria
The absence or failure of some component
of the immune system results in increased
susceptibility to infection.
HIV attacks lymphocytes and is the major
cause of acquired immunodeficiency in
adults.
Tuberculosis (TB) survives within
phagocytes and avoids immune detection.