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9.4 Search for better health: 7. Modern strategies
Extract from Biology Stage 6 Syllabus (Amended October
2002). © Board of Studies, NSW
[Edit: 13 Jun 06]
Background
Modern knowledge of disease has led to the development of a wide range of strategies to prevent and control disease.
discuss the role of quarantine in preventing the spread of disease and plants and animals into Australia and across regions of Australia.
- Australia has generally been fortunate in preventing the spread of plant and animal disease from other parts of the world because of its geographical isolation. Quarantine seeks to prevent the entry of harmful diseases into Australia and to stop the spread of diseases within Australia.
- These diseases cause huge financial losses to farmers in other countries. Australia is able to sell its products to overseas markets because of the absence of diseases, like mad cow disease and foot-and-mouth.
- Australia also has declared fruit-fly free areas where the produce is sold with a guarantee of no fruit fly. This can be done by having inspections and bins to put fruit in when entering particular fruit growing areas.
perform an investigation to examine plant shoots and leaves and gather first hand information of evidence of pathogens and insect pests
- To perform this investigation, you may need some background
information to aid identification of the pathogens. Use gardening books or
the Internet to gather pictures of plant diseases, such as the following:
- Plant diseases
Iowa State University Entomology Department,
USA provides you with a lot of photos of plants that have been attacked
by different diseases and pests.
- Damping off of seedlings, Ohio State University,
USA
This is caused by a fungus. Read the information about the fungal disease and then read about an Australian example. - Attacks by aphids , scale insects and other insects. University
of Kentucky, USA Although this is an American website, aphids are found
in Australia too, so this site will provide you with useful information.
Plants that are commonly infested with aphids are roses. If you or your
neighbours have roses, look on the underside of the leaves to see if there
is any sign of aphids.
- Plant diseases
- When you know what several plant diseases look like, go to an area of vegetation (such as a garden, park or area of bush) and examine plant shoots and leaves to gather evidence of plant diseases caused by pathogens or insect pest attack. You should aim to identify at least two examples of pathogens and insect pests if possible. Look for black patches on the leaves, white powdery residue or other spots that indicate a pathogen such as a fungus, or holes in the leaves caused by insect pests such as catepillars. Use a hand lens to observe the symptoms.
- For each example, record observations systematically and use the evidence to suggest what kind of organism has caused the disease.
explain how one of the following strategies has controlled and/or prevented disease:
- public health programs
- pesticides
- genetic engineering to produce disease resistant plants and animals
Public health programs
- These provide quarantine, sanitation, safe drinking water and immunisation. They are also responsible for advertising campaigns that target cancer and AIDS. Examples of successful health campaigns are the Slip! Slop! Slap! skin cancer advertisements, the advertisements that show various dieases that can be caused by smoking and the Grim Reaper series for education about AIDS.
Pesticides
- Pesticides, such as DDT, have been used to destroy
mosquitoes, which are the vectors of some diseases, such as
malaria and dengue fever.
A good example of a strategy to control or prevent disease is the pesticide control of the disease malaria. Adult mosquitoes can be destroyed by chemicals such as DDT, dieldrin, or by safer chemicals, such as pyrethrums. In 1956, the World Health Organisation was responsible for a major campaign using a residual form of DDT. DDT has been banned in many countries of the world because of its harmful ecological effects, but it is still used for mosquito eradication in malarial areas. This has rid many areas of the world from malaria but has unfortunately not reduced it globally and malaria is still a major killer of children today. Many areas have DDT-resistant mosquitos. Other pesticides, such as organophosphates and pyrethrums, have become popular. In some areas, bed nets have been sprayed with pyrethrums and have been found to be effective in controlling mosquitoes.
Genetic engineering to produce disease resistant plants and animals
- Genetically engineered plants can now kill their own pests because of the insertion of a gene from a soil bacterium, Bacillus thuringiensis (Bt). Bt cotton was the first genetically engineered crop grown in Australia. The bacteria contain a gene that produces chemicals that kill certain insects. By taking that gene from the bacteria and inserting into the genome of plants, the plants now produce the chemical that will kill insect pests.
gather, process information and use available evidence, to discuss the changing methods of dealing with plant and animal diseases, including the shift in emphasis from treatment and control to management or prevention of disease
Background
There has been a shift from waiting for a disease to occur, to preventing the occurrence of the disease. This can be seen in agriculture where genetically resistant crops are grown so that the plants do not have to be sprayed for diseases later in life. Animal and plant diseases have been managed by quarantine restrictions in Australia. Diseases, such as foot and mouth, rabies and plum pox, are managed by not allowing infected organisms to enter the country. World-wide immunisation has caused diseases such as small pox to be eradicated.
- Consider all the aspects of the disease you have studied. Make notes on those aspects that relate to the above syllabus statement.
- Using these notes, plan a discussion of the changing methods of dealing with plant and animal diseases.
- Decide whether you need further information, and if so,
gather it from textbooks or the Internet.
- National resposibilities CSIRO's Australian Animal Health
Laboratory (AAHL), East Geelong, Victoria
- Quarantine AQIS, Australia
- Immunisation Australian Academy of
Science
- National resposibilities
- Write a short concise response from the available evidence
to show what you deduce about the shift in emphasis from treatment and control
to management or prevention of disease. Make sure the response has:
- an introductory paragraph, written in general terms
- a series of paragraphs that focus on specific issues. Each paragraph could discuss any debatable issues, e.g. advantages and disadvantages of a particular approach
- a concluding statement, providing your position or recommendations based on your evaluation.
process and analyse information from secondary sources to evaluate the effectiveness of quarantine in preventing the spread of plant and animal disease into Australia or across regions of Australia
- Use the Internet to obtain and process
information from a range of sources, including the Australian
Quarantine and Inspection Service (
AQIS ) about the control of the
movement of plants and animals and their products into
Australia and within Australia. Quarantine prevents entry
of goods that may carry diseases or pests at airports and
seaports. Affected goods are destroyed. Fumigation is also
part of the quarantine program.
- The sites linked below may assist your evaluation.
- Disease Management:quarantine Plant pathology, School
of biological sciences, Sydney university
- Emerging diseases Ready and waiting? by Dr Tim Mahoney,
Australian Academy of Science, Conference Proceedings, The Shine Dome, Canberra,
19 October 2004. This is a transcript of a talk given at the conference so
I would only look at it if you don't mind the academic language.
- Disease Management:quarantine
- Anaylse this information to evaluate the effectiveness of quarantine regulations in Australia, being sure to identify relationships as well as contradictions in the information.
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