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://ww

w.personal.psu.edu/faculty/j/e/jel5/m

icro/pasteu32.jpg

Louis Pasteur’s classic 1860s experiment

http://bricker.tcnj.edu/micro/m

icro1.html

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

Pasteurized broth

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

http://bricker.tcnj.edu/micro/le1/koch.gif

Mouse dead from anthrax

Colonies injected into

healthy mouse

Blood drawn and placed in petri dish to culture

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://ww

w.petjanitor.com

/health_concerns.htm

Fungi•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://ww

w.apsnet.org/education/IllustratedG

lossary/PhotosI-M

/mildew

.htm

http://www.lib.uiowa.edu/hardin/md/ringwormpictures.html

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

http://www.cat.cc.md.us/courses/bio141/labmanua/lab1/u1coccus.html

Bacilli cause

tuberculosis

Vibrio cause cholera

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.

•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.

•One of the most complex viruses is the one that infects bacteria, such as this bacteriophage.

•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.

25nm

50nm

Viruses

•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.

•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

50nm

Viruses

•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 - Prion protein in its normal folding configuration.

B - The proposed configuration of the protein that can cause infection.

A. B.

Prions

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.