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Infectious Disease


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Senior Biology - Infectious Disease - For additional resources visit:

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Infectious Disease

  1. 1. Infectious Disease Sarah Jones
  2. 2. What is a healthy organism? Health is the wellbeing of the organism. All our body functions, which are under the control of our genes, work together to maintain health.
  3. 3. Disease is any condition that adversely affects the function of any part of a living thing.
  4. 4. An infectious disease is one that is caused by an organism and that can be transferred from one person to another. The transfer may be directly from person to person, or it may be carried out by a vector, such as a blood- sucking insect.
  5. 5. Examples of infectious diseases are colds, influenza, chicken pox, herpes and measles. Hepatitis C Virus
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  7. 7. Impact of Infectious Diseases on Development of Human Societies - an interesting link from Miami University on microorganisms and human disease.
  8. 8. • Link to CDC (Centers for Disease Control and Prevention) • Link to WHO (World Health Organization)
  9. 9. Non-infectious diseases are diseases that are not due to disease-causing organisms. They include genetic diseases, such as Down syndrome, haemophilia, and those that are related to lifestyle or environment, such as cardiovascular disease and skin cancer.
  10. 10. Agents of Disease
  11. 11. Organisms are called pathogens when they cause disease. To cause disease, organisms need the right conditions to multiply and be transmitted. Ebola Pathogens
  12. 12. An infectious disease is caused by a pathogen and can be passed from one organism to another e.g. Bacteria, Protozoans, Fungi, Viruses, and Prions
  13. 13. Research and give an example of each of the following pathogens. • Bacteria • Protozoan • Fungi • Virus • Prion
  14. 14. How are diseases spread? • Airborne • Contact • Faeces • By other organisms • The Asian tiger mosquito is responsible for the transmission of dengue and yellow fever plus 20 other viral diseases.
  15. 15. Pathogens and Epidemics During the Middle Ages waves of infectious diseases such as cholera and plague swept through Europe. Plague victims being blessed by a priest
  16. 16. • Link to Hartford University Article on the History of Plagues • Until the mid-19th century most people believed that living things came into existence by spontaneous generation.
  17. 17. Macroparasites Macroparasites are large parasites that can be seen with the naked eye. They may be internal or external parasites. Examples of internal include, tapeworms, roundworms and flukes. External parasites include lice, ticks and fleas.
  18. 18. Kinnear and Martin, Nature of Biology, 2006
  19. 19. Immune Response – The Body's Response to Micro-Organisms Flu Pneumonia German Measles
  20. 20. Identifying Microbes That Cause Disease During the second half of the nineteenth century, the work of Pasteur and Koch and other scientists stimulated the search for microbes as causes of disease.
  21. 21. Louis Pasteur • Solved the mysteries of rabies, anthrax, chicken cholera, and contributed to the development of the first vaccines. • Debunked the widely accepted myth of spontaneous generation. • Described the scientific basis for fermentation, wine-making, and the brewing of beer.
  22. 22. Robert Koch Robert Koch was a German physician and bacteriologist. He was awarded the 1905 Nobel Prize in physiology or medicine for developing a test used in diagnosing tuberculosis. He isolated the bacilli causing anthrax, tuberculosis, and Asiatic cholera. Koch developed a vaccine for treating anthrax and rinderpest. (Source: How Stuff Works, 2009)
  23. 23. Koch described the criteria which must be met if we are to be sure that a particular microorganism causes a particular disease. Koch's Postulates 1. The specific microorganisms must be present in every host with the disease. 2. The specific microorganisms must be isolated from the host and grown in a pure culture. 3. A potential host, when inoculated with the microorganism, must develop the same symptoms as the original host. 4. The specific microorganism must be able to be isolated from the second host and identified as the same species as originally cultured.
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  25. 25. The Role of Antibiotics Antibiotics destroy or inhibit the growth of bacteria. They are chemicals that act selectively on pathogens without destroying the host. They are not effective against viruses. Alexander Fleming discovered the first antibiotic, penicillin, in 1928.
  26. 26. Bodies Defence 1. Physical (skin and mucous) 2. Nonspecific defensive cells (phagocytes, white blood cells, inflammation and fever) 3. Immune Response (lymphatic system- recognition of foreign cells)
  27. 27. Our bodies contain very large numbers of bacteria (approximately 15% of your body weight) and many of those in the intestine are essential for our wellbeing (microflora).
  28. 28. Defence Barriers • Skin • Mucous membranes • Cilia • Chemical barriers • Specific response - Immune response
  29. 29. Kinnear and Martin, Nature of Biology, 2006
  30. 30. • Inflammation response • Phagocytosis • Sealing off the pathogen Electron Micrograph of a Macrophage Phagocytosis of E. coli Defence Adaptations – Non-Specific Responses
  31. 31. Types of Immunity Non-specific immunity involves many physical and chemical barriers to infection and is not affected by prior contact with a particular micro- organism. It has no ‘memory’ of a prior infection. Kinnear and Martin, Nature of Biology, 2006
  32. 32. Specific immunity involves the production of antibodies which act against a particular infection. Specific immunity has a ‘memory’ so that when another infection from the same organism occurs, an increased response is obtained. Kinnear and Martin, Nature of Biology, 2006
  33. 33. The Immune Response The key to a healthy immune system is its remarkable ability to distinguish between the body’s own cells (self) and foreign cells (nonself).
  34. 34. The body’s immune defences normally coexist peacefully with cells that carry distinctive "self" marker molecules. But when immune defenders encounter cells or organisms carrying markers that say "foreign," they quickly launch an attack.
  35. 35. Anything that can trigger this immune response is called an antigen. An antigen can be a microbe such as a virus, or even a part of a microbe.
  36. 36. Tissues or cells from another person (except an identical twin) also carry non-self markers and act as antigens. This explains why tissue transplants may be rejected.
  37. 37. Phagocytes and Killer Cells Phagocytes are white blood cells that engulf and destroy micro-organisms and other foreign materials that enter the body. Phagocytes are produced by cells in the bone marrow and include neutrophils, the most common of the white blood cells, and monocytes, the largest of the white blood cells. Kinnear and Martin, Nature of Biology, 2006
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  39. 39. • When we are exposed to an antigen for the first time, our body responds by producing lymphocytes. • Lymphocytes are a type of white blood cell; the two main types are T cells and B cells (also called T lymphocytes and B lymphocytes).
  40. 40. All lymphocytes are produced in the bone marrow. Some mature in the bone marrow into B lymphocytes or B cells. Other lymphocytes leave the bone marrow before they are fully developed and travel to the thymus gland where they differentiate into mature T lymphocytes or T cells. (T cell stands for ‘thymus- dependent’ cell.) Kinnear and Martin, Nature of Biology, 2006
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  42. 42. B cells have immunoglobulins on their surfaces. Immunoglobulins are proteins that identify antigens. Immunoglobulins are also called antibodies. The immunoglobulins of each B cell have a specific structure and recognise only one kind of antigen. Kinnear and Martin, Nature of Biology, 2006
  43. 43. • When T cells mature in the thymus, many different kinds of T cells are produced which recognise many different antigens. T cells do not make antibodies. There are different types of T cells and each type reacts with other cells in the immune response. • Immunity involving T cells and phagocytes is called cellular immunity. Kinnear and Martin, Nature of Biology, 2006
  44. 44. Phagocytes that have ingested foreign material carry some of the foreign antigen on their surfaces. Helper T cells (Th), recognises these antigens and stimulates B cells. B cells will not reproduce and form plasma cells without this assistance from Th cells. Kinnear and Martin, Nature of Biology, 2006
  45. 45. Cytotoxic T Cells • Kill body cells that have been infected with a virus. Tc cells kill the infected cell by secreting proteins that punch holes in the membrane of the cell and the contents ooze out. • Tc cells cannot kill isolated virus particles. They can kill the virus only when it is inside a cell. • Some Tc cells also destroy cancer cells. Kinnear and Martin, Nature of Biology, 2006
  46. 46. The Lymphatic System Kinnear and Martin, Nature of Biology, 2006
  47. 47. How T and B Cells Travel • B and T cells develop from primary lymphoid tissues: bone marrow and thymus. • The immune system also contains a number of other lymphoid tissues and organs: the spleen, tonsils and lymph nodes, which are connected by a network of lymphatic vessels. Kinnear and Martin, Nature of Biology, 2006
  48. 48. • Lymphatic vessels contain lymph, which drains from nearby tissues. Memory T and B cells, in particular, circulate in the lymph, ready to react with their antigens. • Antigens that enter the body are carried in lymph to a lymphatic organ where there is a high concentration of white cells. • Large numbers of lymphocytes (mainly B cells) reproduce by mitosis. As a result, your lymph nodes can become swollen and sore. Kinnear and Martin, Nature of Biology, 2006
  49. 49. What are the ethical concerns in the research and implication of vaccines?
  50. 50. Research and explain how Herd Immunity works.