1. Control Measures for Infectious Diseases Personal behavior Vaccination Vector control Disinfection –Removal –Inactivation Prevention or Cure

2. Personal behavior Exposure avoidance Handwashing Skin protection Respiratory protection Prophylactic treatment

3. The body’s defenses Skin (passive) Non-specific immune responses –Inflammation (cytokines, macrophages, activated lymphocytes), fever –Phagocytosis by macrophages –Antibody response: IgA, IgM Specific immune responses –Antibody production: IgG specific to target –Memory cells (B-lymphocytes)

4. Cells of the Immune System Bone Marrow Stem Cells Blood lineage Red Blood Cells Platelets Granulocytes Eosinophils, Neutrophils, Basophils Monocytes Macrophages Lymphoid lineage (lymphocytes) NK Cells Pre-B Plasma cells Memory B-cells Pre-T (thymus) T-helper cells T-suppressor cells Memory T cells Cytotoxic T cells Delayed hypersensitivity T cells

5. Vaccination Develop antibodies – attenuate disease Personal or public health measure ? Need to have “critical mass” vaccinated to achieve control of epidemic Practical considerations: cost, side- effects, duration of immunity

6. Some examples Smallpox Flu “Childhood diseases” –Measles, chickenpox Rotavirus Bacterial diseases ? –Tetanus –Anthrax

7. Routes of Transmission Person-to-person: Physical contact Indirect person-to-person –Aerosol –Fomites Vehicle-borne –Food, water Vector-borne –Insects

8. Vector-borne cycle of infection Disease agent is a microorganism Reproduces in a reservoir or host Is transmitted by a vector

9. Vector-borne cycle of infection Example: West Nile Flavivirus Disease agentTarget organisms Reservoirs ? Vector

10. Vector control Vector-borne diseases –E.g. West Nile, malaria Identify vectors, reservoirs –Information on vector life-cycles Eradicate vectors, reservoirs –How ?

12. Mosquitos Pesticides Larvaecides Malathion Naled (an OP) Synthetic pyrethroids Mosquito traps Drain water pools

13. Insecticides Chlorinated hydrocarbons Organophosphates Carbamates

14. Animal Reservoirs Cryptosporidium parvum Single host, eg Beef, calves Oocyst Oocyst excysts, releases 4 sporozoites Sporozoites invade intestinal epithlial cells Sporozoites replicate asexually, differentiate into microgametes and macrogametes Sexual replication More oocysts

15. Cryprosporidium life-cycle

16. Is vaccination an option ? Vaccinate vectors ? Reservoirs ? Target species ?

17. Attack disease agent directly Inside host – antibiotics ? In transmission media –Fumigation, sanitization, sterilization

18. Disinfection Physical –Heat, pasteurize, autoclave –Time/temperature dependence Biological –Predation, competition Chemical –Destroy versus prevent reproduction

19. Water disinfectants Chlorine Chlorine dioxide Chloramines Ozone UV light Effectiveness differs with type of organism

20. Chlorine Strong oxidizing agent Chlorine gas, dissolved in water > hypochlorous acid HOCl at low pH, most effective form Maintains residual Formation of THMs Offensive taste/odor

21. Chlorine Dioxide Weaker oxidizing agent More effective at higher pH Poor residual

22. Chloramines Monochloramine, NH 2 Cl Need chlorine and ammonia gas, generated on-site Weaker oxidizing agent Fewer THMs Less offensive taste/odor Poor residual

23. Ozone O 3 Generated on-site Strong oxidizing agent Effective against Giardia Odor/taste not offensive Poorly water-soluble, no residual

24. Ultra-violet light UVA, UVB, UVC Attacks nucleic acids Less effective in opaque/colored waters No residual