BIOLOGY OF DISEASE

1. BIOLOGY OF DISEASE jrmg 2009

2. What is a Disease? • any change (other than an injury) that interferes with the normal body function • refers to conditions that impair normal tissue function

3. INFECTIOUS DISEASE • caused by infectious agents • can be acquired: • contact with someone carrying the infectious agent • contaminated objects, food, air or water

4. INFECTIOUS DISEASE • spread quickly or at a slow rate • E.g. Polio virus (contagious but not virulent)‏ • Ebola hemorrhagic fever (virulent but not contagious)‏

5. IS DISEASE SYNONYMOUS WITH INFECTION?

6. Disease VSInfection • results from the invasion and growth of a pathogen • tissue function is impaired • results when a pathogen invades and begins growing within a host • bodily function: normal

7. TYPES OF DISEASE • Can be: • Genetic • Cystic fibrosis • Hemophilia

8. TYPES OF DISEASE • Because of aging • e.g. Atherocslerosis, osteoporosis

9. TYPES OF DISEASE • Infectious • German measles • Chicken pox • Malaria

10. WHAT are Pathogens? • microorganisms that are capable of causing disease • infectious agent that causes disease in virtually any susceptible host

11. Opportunistic Pathogens • potentially infectious agents • But….. (healthy immune systems)‏ • Found on… • elderly (immuno suppressed)‏ • cancer patients* (immuno- compromised)‏ • people who have AIDS or are HIV-positive (immuno- compromised)‏

12. Types of Infectious Agents • Viral infections • e.g. colds, influenza, measles, chicken pox, West Nile virus, hepatitis, AIDS

13. Types of Infectious Agents • Bacterial infection • e.g. pneumonia, strep throat, boils, acne, streptococcal infection, bubonic plague, and anthrax

14. OTHER EXAMPLES • Salmonella typhi - typhoid fever, and Yersiniapestis- bubonic plague • Staphylococcus aureus-causes skin, respiratory, and wound infections • Clostridium tetani, which produces a toxin that can be lethal for humans • Staphylococcus epidermidis- acne

15. Types of Infectious Agents • Protozoan infections • e.g. Malaria, amoebiasis and Diarrhea

16. EXAMPLES • Diarrhea: Giardialamblia and Cryptosporidium parvum • Malaria: Plasmodium vivax • Wuchereriabancrofti • Brugiamalayi, or Brugiatimori

18. Types of Infectious Agents • Fungal infections • e.g.yeast infections, ringworm and athlete's foot

19. Candida genus • opportunistic pathogens • vaginal yeast infections and thrush (a throat infection)

20. Types of Infectious Agents • Helminthes Infection • simple, invertebrate animals, some of which are infectious parasites • e.g. Schistosomiasis Liver fluke disease

22. HOW DO THESE INFECTIOUS AGENTS HARM THE HOST???

23. Manner of Inflicting/ Causing Harm to the HOST • entrance the host body • adhere to specific host cells • invade and colonize • multiply between host cells or within body fluids • cause tissue damage • production of toxins or destructive enzymes

24. SO… Infectious agents work… • By… 1. become so numerous that they interfere with normal bodily functions 2. destroys body cells and tissues 3. produce toxins

25. HOW DID THEY FIND OUT THE CAUSE OF THE DISEASE????

26. Studying Infectious Disease • GERM THEORY • states that microorganisms can cause diseases • infectious disease is caused by an infectious agent

27. Studying Infectious Disease • ROBERT KOCH • discovered: • Bacillus anthracis, Mycobacterium tuberculosis , Vibrio cholera • Developed: • use of agar as solid medium. • invented nutrient broth and nutrient agar • KOCH’s POSTULATE • sequence of experimental steps for directly relating a specific microbe to a specific disease

28. KOCH’s POSTULATE • suspected pathogenic organism • present in all cases of disease • absent for healthy animals • suspected organism should be grown in cultures, in vitro but can also be in vivo (in animals)‏ • cells from a culture of suspected organism should cause disease in healthy animals • organisms should be re-isolated and shown to be the same as original

30. Modes of Infection • Direct contact- infected by contact with the reservoir • i.e. touching an infected person • ingesting infected meat • being bitten by an infected animal or insect. • includes inhaling the infectious • engaging through intimate sexual contact

31. Modes of Infection • Indirect contact • when a pathogen can withstand the environment outside its host for a long period of time before infecting another individual • Inanimate objects that are contaminated by direct contact with the reservoir • The fecal-oral route of transmission

32. Modes of Infection 2. Air- borne (droplet infection)‏ • e.g. colds, flu, sinus infections, German measles, pneumonia, meningitis, TB and SARS

33. Modes of Infection 3. Contact • e.g. chicken pox, small pox, syphilis, gonorrhea

34. Modes of Infection 4. Vectors- carry disease through other animals (e.g. insect bites)‏ • e.g. typhus, rabies, H- fever, malaria, dengue

35. How do our body defend us from diseases? • Nonspecific mechanisms A. Structural Defense • Skin, mucous membranes • perspiration (salts and fatty acids)‏ • tears (contain lysozyme which can break down bacterial cell wall)‏ • acid secretion in stomach (HCl)‏ • B.Cellular • Phagocytosis • e.g. leucocytes in WBC • FEVER

36. How do our body defend us from diseases? • Specific mechanisms of host resistance • white blood cells called lymphocytes: • T-cells (produced from lymphocytes that matured in the thymus gland)‏ • B-cells (produced from lymphocytes that matured in the bone marrow).