Download Pathogens and Disease

Pathogens
and
Disease
Infections and how to prevent them
What is ‘health’?
•Before we can begin to discuss ‘disease’ we must consider what
is meant by the term ‘health’.
•My pocket Collins dictionary states ‘health’ as a soundness of
body. Is this really a satisfactory definition?
•My encyclopedia version of the Websters dictionary states that
‘health’ is the state of fitness of the body or of the mind. Is this
more encompassing of what ‘health’ really means.
•‘Health’ is actually very difficult to define as it contains many
components such as physical, physiological, behavioural and
social characteristics.
•On top of this different people will have different ideas of what
being in good health means to them.
Staying healthy
•There are many ways we can behave in order to maintain health, that is …to
stay healthy;
•If we lead a healthy lifestyle we usually eat healthy food and partake in
health promoting activity such as plenty of sleep and exercise.
•Our bodies also automatically look after us as well;
•Mitosis replaces dead cells and allows us to grow
•Our genes make sure the correct proteins are made as our body needs
them. There are also DNA repair genes that produce enzymes that ensure
the DNA is copied correctly and genes that stop or slow cell growth such
as in tumors (if these genes are damaged we can suffer from cancer)
•Cell differentiation and specialisation allows cells to be suited to a
particular function. For example white blood cells make up part of our
immune system and help us fight disease
What is ‘disease’?
•Disease is a condition that impairs or interferes with the normal
functioning of the body. Disease compromises health (which is
why it is important to be able to define ‘health’ adequately).
•Diseases can be broken down into two main categories:
infectious and non-infectious.
•An infectious disease in one that is contagious and can be passed
from one organism to another by an infectious agent/organism
known as a pathogen that invades the body.
•Non-infectious diseases are caused by genetics, nutrition,
chemicals or environmental factors and do not involve a
pathogen. Non-infectious diseases will be covered in a later
PowerPoint. In what way can non-infectious diseases be passed
on from one person to another?
Characteristics of Pathogens
•Pathogens are parasites that can be microscopic or macroscopic.
•Pathogens can live in the air, the soil, water, food products, on
our skin or on our internal organs.
•Pathogens can pass from one person to another either by direct
contact or by indirect contact.
Personal hygiene helps control disease
•Cleanliness prevents contamination of items that could come in
contact with our body by stopping them from entering the body.
•For a long time humans have realized the important of
cleanliness in maintaining health.
•The Ancient Romans built sewers to remove human wastes
away from their homes. (Pathogens live off the nutrients)
•The Chinese and Hebrews undertook hygienic lifestyles even
3,000 years ago.
•Today we wash our hands before eating, cook food properly,
treat our sewage, provide uncontaminated drinking water for
everyone, hold our hand over our mouth when we cough, cover
open sores and so on.
Quarantine in Australia
•The Australian Quarantine and Inspection Service (AQIS)
helps to prevent the spread of disease into and across
Australia.
•Upon entering Australia, all plant and animals products are
kept in strict quarantine and must be declared at customs in
order for this to take place.
•This protects native Australian flora and fauna as well as the
health of the human inhabitants.
•Fruit and vegetables cannot be carried through parts of
Victoria, NSW, Queensland and South Australia in order to
prevent disease moving from one state to the next.
Genetic engineering and disease
resistance
•Transgenic organisms are being produced with a variety of
novel qualities for their particular species. One aspect of
genetic engineering is to produce organisms with increased
resistance to disease.
•A genetically engineered striped bass is being developed
with insect genes in order to increase disease resistance.
•A tomato is being developed with resistance to bacteria.
Louis Pasteur (1822-1895)
•Pasteur was a French chemist who discovered that ‘germs’ or
micro-organisms were the cause of infectious disease.
•He studied soured wine and found that it contained small rod like
microbes as well as the yeast that was found alone in non-soured
wine.
•Previously people thought maggots came to be spontaneously.He
disproved the theory of ‘spontaneous generation’ supporting the
cell theory showing that new cells were produced from existing
cells.
•He produced a technique of heating fluid to 550C for 30 minutes
to kill microorganisms responsible for souring it. This became
known as Pasteurization and is still used today.
Louis Pasteur (1822-1895)
http://www.personal.psu.edu/faculty/j/e/jel5/micro/pasteu32.jpg
Louis Pasteur’s classic 1860s experiment
http://bricker.tcnj.edu/micro/micro1.html
Pasteurized
broth
Swan neck flask prevented the
microbes from entering the
sterile flask
Once the fluid
came in contact
with the air it
became
contaminated and
was no longer
sterile
Robert Koch (1843-1910)
•A physician who discovered
that microorganisms are present
in every host with an infectious
disease.
•Worked initially with anthrax –
a bacteria killing many sheep
and cattle.
•Wrote a list of criteria needed
to prove a particular organism
caused a particular disease –
known as Koch’s postulates.
http://www.museumsnett.no/ntm/medisinskmuseum/sunn_sjel/bakteriologi.htm
Koch’s Postulates
1. The organism responsible for the disease must always be
present when the disease occurs
2. The organism must be isolated from the host and grown in
pure cultures in the laboratory
3. Organisms from this pure culture can be inoculated (injected)
into healthy organisms that then produce the disease
4. The organism must them be re-isolated, grown again in pure
culture and compared with the first organism that was
originally isolated
Mouse dead from
anthrax
Colonies
injected into
healthy mouse
Blood
drawn and
placed in
petri dish
to culture
http://bricker.tcnj.edu/micro/le1/koch.gif
Colonies
grow
Mouse dies.
Blood is drawn
and cultured in
petri dish
Colonies are compared to
the original ones grown
from first dead mouse
Macro-parasites
•Macroparasites can be seen with the naked eye
•Endoparasites live inside a host and include tapeworm in
mammals
•Ectoparasites live on the outside of the host and include tics,
fleas, and mites in mammals
•Aphids are ectoparasites that live on plants by tapping into the
sugar carried in the phloem
EM of an
aphid x68
Macro-parasites
•http://www.petjanitor.com/health_concerns.htm
•Eukaryotic organisms that can be unicellular (yeast) or
multicellular (mushrooms). They can be parasitic (living on a
host) or saprophytic (living on dead material)
•Examples include tinea (athletes foot) in humans and mildew
in plants. Fungal spores cause this in plants.
http://www.lib.uiowa.edu/hardin/md/ringwormpictures.html
http://www.apsnet.org/education/IllustratedGlossary/PhotosI-M/mildew.htm
Fungi
Protozoans
•Protozoans are microscopic
single cells eukaryotes of
which only a few are
pathogens.
•Examples include malaria
and amoebic dysentery.
http://www.medartist.com/malaria.jpg
Bacteria
•Prokaryotes with no membrane bound organelles and a single
strand of DNA. Approximately 0.5 – 5.0 µm in size.
•Most are actually useful to our everyday lives, a few are
harmful such as tuberculosis, tetanus and syphilis in animals and
crown gall in plants.
•Bacteria produce toxins as waste products that harm the host.
Bacteria are classified by their shape.
http://www.worldinter.net/~tomato/graphics/3crngall.gif
Bacteria
Bacilli
cause
tuberculosis
Vibrio
cause
cholera
http://www.cat.cc.md.us/courses/bio141/labmanua/lab1/u1coccus.html
Viruses
•Non cellular protein coated package of DNA approximately
30-300 µm in size.
•Discovered in the last 50 years due to the development of the
electron microscope.
•Uses the host cells to reproduce its own DNA and in doing so
destroys the hosts cell.
•Examples include Influenza in mammals and tobacco mosaic
virus in plants.
Viruses
•One of the most complex
viruses is the one that infects
bacteria, such as this
bacteriophage.
25nm
•We are all familiar with
the influenza virus!
•This virus has a
membranous envelope
that is partly made from
the hosts cell membrane.
This makes it more
infectious to the host.
•It has a polyhedral head that
contains the DNA.
•The tail fiber attaches to the
bacteria and the DNA is injected
into the bacterial cell.
50nm
Viruses
•The adenovirus causes respiratory
tract infections in animals.
•It has 252 identical proteins that
make up its polyhedral capsid. At
each vertex is a protein spike.
10nm
•Tobacco mosaic stunts the
growth of tobacco plants and
produces a mottled (mosaic)
pattern on the leaves.
•It has a helical capsid (coat)
made of thousands of molecules
of a single type of protein.
•Its overall shape has a rigid, rod
like appearance.
50nm
Prions
•Prions are proteins that manage to produce
themselves in their host.
•The proteins are abnormally folded and
then have the ability to infect other proteins
so that they also fold abnormally.
•They have no genetic material in them.
•They attack the brain causing small holes.
Humans and animals alike suffer dizziness,
nausia and seizures which eventually lead to
death.
•Examples include ‘mad cow’ or BSE
(Bovine Spongiform encephalitis) disease in
cattle and CJD (Creutzfeld-Jacob Disease)
in humans.
•Infection is caused by eating neural tissue
A.
B.
A - Prion protein in its normal
folding configuration.
B - The proposed
configuration of the protein
that can cause infection.
The End
http://www.nearingzero.net/index.html
References
•Aubusson, P. and Kennedy, E. (2000) Biology in Context. The Spectrum of Life
Oxford University Press, Melbourne, Australia.
•Board of Studies (2002) STAGE 6 SYLLABUS Biology Board of Studies, NSW,
Australia.
•Bricker, J. (2002) Microbiology Retrieved from the site
http://bricker.tcnj.edu/micro/micro1.html April 2004.
•Collins English Gem Dictionary (1975) Collins & Co. Ltd. Great Britain.
•Humphreys, Kerri (2002) The Search for Better Health. Science Press, Australia.
• Kim, Nick [no date] Nearing Zero retrieved from website
http://www.nearingzero.net/index.html January 2004.
•Kinnear, J and Martin, M (2001) Biology 2 HSC Course: Jacaranda HSC Science
John Wiley & Sons, Australia, Ltd.
References
•Lexicon (1988) Webster’s Dictionary of the English Language, Encyclopaedic
Edition, Lexicon Publications, INC, New York.
•Kaiser, G (2004) Webpage for Dr. Kaiser’s Microbiology Course Retrieved form the
site http://www.cat.cc.md.us/courses/bio141/labmanua/lab1/u1coccus.html April
2004.
•Mudie, K. et.al. (2000) Heinemann Biology Malcom Parsons, National Library of
Australia, Australia.
•Norwegian Museum of Science & technology (2004) Retrieved from the site
http://www.museumsnett.no/ntm/medisinskmuseum/sunn_sjel/bakteriologi.htm April
2004.
•Pet Janitor Inc. (2003) Pet Janitor Retrieved from the site
http://www.petjanitor.com/health_concerns.htm April 2004.
•University of Iowa (2004) Pictures of Ringworm Retrieved from site
http://www.lib.uiowa.edu/hardin/md/ringwormpictures.html April 2004.