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Disease and Epidemiology

Disease and Epidemiology. What is Disease? . Any condition that jeopardizes the survival of an organism in a particular environment. What is epidemiology?. The study of the causes, distribution, and control of disease in populations. . Some Characteristics of Disease.

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Disease and Epidemiology

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  1. Disease and Epidemiology

  2. What is Disease? • Any condition that jeopardizes the survival of an organism in a particular environment What is epidemiology? The study of the causes, distribution, and control of disease in populations.

  3. Some Characteristics of Disease • Change of normal appearance, behavior, or movement • Fever • Dull, inflamed eyes • Rough-soiled hair, fur or feathers • Difficulty walking or running • Abnormal lumps • Discoloration/lesions of skin

  4. Disease causing entities • Any agent that may bring abnormal condition to any or all of the tissues of the body via eggs, contact, food or a vector • 2 Types of disease causing entities: • Infectious agents – caused by a pathogen (bacteria, virus, parasites etc), invade the body and multiply there. • Noninfectious agents –caused by something other than pathogens. (carcinogens, environmental, etc.)

  5. Bacteria Viruses Parasites Prions (Mad Cow Disease) Infectious Agents -pathogen – an infectious disease causing agent

  6. Noninfectious agents • Injuries • Mutations, genetic • Poisons and chemicals • Poor nutrition

  7. For disease to occur and spreadcertain conditions must be met Chain of infection

  8. To grow and spread, most microorganisms prefer • Warm, dark environment • Moisture • Source of food • Human body fits the criteria!

  9. 2. Reservoir • A place the pathogen can live • Human body • Animals • Environment • Fomites: contaminated inanimate objects-

  10. 3.Portal of Exit • Way of leaving the reservoir in which it has been growing: • Blood • Tears • Feces • Urine • Saliva • Draining wounds

  11. 4. Means of Transmission- • Needs to be transported to another reservoir Direct person to person contact- contaminated hands most common Indirect contact- coming in contact with contaminated equipment, food, insect bite

  12. 5. Portal of Entry • Breaks in skin • Breaks in mucous membranes • Respiratory tract • Digestive tract • Circulatory system • Genitourinary tract

  13. How your body fights off a causative agent • Mucous membranes-trap • Cilia – transport. • Coughing and sneezing-- expel • Hydrochloric acid in the stomach-- destroy • Tears in the eyes-bacteriocidal • Fever-destroy • Inflammation-white cells • Immune response-antibodies

  14. Antibodies and antigens

  15. 6. Susceptible host • Large numbers of pathogens. • Body defenses are weak Results in susceptible host, or a person likely to get an infection or disease Chain of infection can be broken at any point

  16. The spread of infectious diseases • DIRECT CONTACT: touching or other direct contact with bodily discharges, secretions or waste, an open wound, bandage, soiled objects or infected surface; STD, blood borne • FECAL-ORAL – eating or……. • ASYMPTOMATIC CARRIER – an infected person such as“Typhoid Mary” • VEHICLE An inanimate object which serves to communicate disease. For example, a glass of water containing microbes, or a dirty rag, etc. • VECTORS (such as arthropods – “bugs”) VECTOR – A live organism that serves to communicate disease. For example, mosquitoes and other arthropods. • Airborne/droplet

  17. two types of vectors: mechanical and biological. Microbes do not multiply within mechanical vectors - only physically transport microbes from host to host. In contrast, microbes must propagate within a biological vector before it can transmit the microbes. • mosquito (malaria, St. Louis encephalitis, dengue fever, yellow fever, West Nile virus) • flea (bubonic plague) • tick (Lyme disease, rocky mountain spotted fever, tick-borne encephalitis) • deer mouse (hantavirus) • kissing bug (Triatominae) (Chagas Disease) • bat(Rabies)

  18. “Typhoid Mary” Mallon -- was a cook in the New York City in the 1900s • she infected 22 people with typhoid fever, one of whom died. Eventually estimates ran as high as 50 deaths attributed to her. • Dr. George Soper interviewed Mary, and suggested there might be a connection between the dishes she served and the outbreaks of typhoid. • After forcibly obtaining urine and stool samples, it was revealed she was an asymptomatic carrier of typhoid salmonella • In 1915, a serious epidemic of typhoid erupted among the staff of New York's Sloan Hospital for Women, with twenty five cases and two deaths. City health authorities investigated. • Mary was quarantined for life on North Brother Island. She became something of a celebrity, and was interviewed by journalists (who were forbidden to accept as much as a glass of water from her.) She died in 1938 of pneumonia.

  19. Charting the Spread of a Disease *Investigator must work backwards to try and determine the index case *The mode of transmission/vector *The “waves” of infection

  20. Incubation Period • Time period before signs and symptoms appear • The delay is used for the pathogen to multiply • Varies with each disease: • Colds about 7 days • HIV can be 10 years

  21. Pathogen - a disease causing agent (example: bacteria, viruses) Virulence – ability of a pathogen to overcome the body’s defense & produce a disease Host – any organism serving as a residence for a pathogen Vector – agent/entity that delivers a pathogen to a host, intermittent host Infectious Disease Causing Agents

  22. Bacteria • Smallest & simplest form of life • prokaryotic • Single-celled • Have a cell wall • Vary in size & shape • Many are beneficial • decompose and recycle nutrients • Foods – yogurt, wines, cheese • Aid in digestion

  23. Bacteria Characteristics 1. Two Domains: Archaebacteria – live in extreme conditions Eubacteria – all other bacteria

  24. 2. Oxygen need No oxygen (anaerobic) – such as botulism, tetanus Oxygen required (aerobic) Facultative anaerobic – prefers oxygen, but can survive in anaerobic conditions Distinguishing Characteristics of Bacteria

  25. 3. Prokaryotic No membrane bound organelles such as a nucleus or mitochondria

  26. Microscopic 4. ________________ How big are bacteria? http://www.cellsalive.com/howbig.htm 5. Where do they live? Archaebacteria - live in extreme harsh environments – hot temperatures, extreme salinity for example and include halophiles, methanogens, thermophiles, sulfophilic strains Eubacteria - bacteria we encounter on a daily basis – E. coli for example

  27. 6. Shape: b. a. c. Spherical - cocci Helical or Spiral Rod - bacillus Vibrio– comma shaped

  28. 7. Staphylococcus Streptococcus

  29. -Some are rigid, Some flexible 8. Have Cell Walls 9. Form Endospores in Harsh Conditions

  30. Distinguishing Characteristics of Bacteria • Cell wall absorb “gram’s stain”? • Gram positive – retain stain in cell walls • Gram negative – characteristic of many pathogenic strains, may not always respond to anitbiotics • Ability to release toxins – waste products from metabolism • http://www.microbelibrary.org/microbelibrary/files/ccImages/Articleimages/keen/Gramstainkeen.htm

  31. Bacteria release toxins…………not good!! • Chemical substances harmful to the normal functioning of cells • Endotoxins – parts of bacterial cells • Exotoxins – wastes from bacterial cells • _______________- disrupt the transmission of nerve impulses. Neurotoxins

  32. Bacteria divide by Binary Fission

  33. Bacteria exchange genetic information by conjugation-- no new cells are created-- leads to exchange of antibiotic genes http://www.hhmi.org/biointeractive/animations/conjugation/conj_frames.htm

  34. Bacterial Diseases 1. Anthrax - respiratory infection initially presents with cold or flu-like symptoms for several days, followed by severe (and often fatal) respiratory collapse Cutaneous Inhalation

  35. 2. Tuberculosis

  36. 3. Typhoid fever - caused by the bacteriumSalmonella Typhi. Common worldwide, it is transmitted by ingestion of food or water contaminated with feces from an infected person.

  37. 4. Diphtheria an upper respiratory tract illness

  38. 5. Botulism

  39. 6. Tetanus

  40. 7. Gonorrhea STD

  41. 8. Syphilis STD

  42. 9. Chlamydia STD

  43. Bacterial Disease Treatments ANTIBIOTICS • Inhibit growth of some bacteria – may disrupt cell walls, or other metabolism • products of fungus or competing bacteria • -- Ex: Penicillin, erythromycin, kanamycin, tetracycline…… • Bacteria can _______________to become resistant to antibiotics mutate

  44. Make milk into yogurt! Make antibiotics! Treat Wastewater! Aid Digestion! Pesticide Control! Also-- Decomposers/ Natural Cycle! Bioremediation! Food/Preservatives! Helpful Bacteria © Eric MacDicken


  46. Viruses • Microscopic in size – smaller than bacteria • Not considered to be living • Can cause serious, contagious disease • Classified by • type of tissue they invade, • appearance, • host they normally infect • Type of genetic material – DNA or RNA

  47. Virus Characteristics DNA inside Chicken Pox Human Influenza Rabies Virus HIV

  48. Viruses – Structure • Protein coat • geometric shapes • Receptor proteins to match virus with specific host cell • Genetic element • Either DNA or RNA strand

  49. Two Types of Virusesa. Lytic (virulent)b. Lysogenic (temporal) – “dormant”http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter17/animation_quiz_2.htmlhttp://www.cfoxscience.com/mrfox/apbio/Lectures/lysogenic_pathway.swf

  50. LYTIC CYCLE • Viral genetic element (DNA or RNA) becomes part of host cell DNA • Host cell produces new viruses • Cell lyses (is destroyed) thereby releasing viruses to invade other host cells

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