control measures for infectious diseases
DESCRIPTION
Control Measures for Infectious Diseases. Personal behavior Vaccination Vector control Disinfection Removal Inactivation. Prevention or Cure. Personal behavior. Exposure avoidance Handwashing Skin protection Respiratory protection Prophylactic treatment. The body’s defenses. - PowerPoint PPT PresentationTRANSCRIPT
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Control Measures for Infectious Diseases
• Personal behavior
• Vaccination
• Vector control
• Disinfection– Removal– Inactivation
Prevention or Cure
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Personal behavior
• Exposure avoidance
• Handwashing
• Skin protection
• Respiratory protection
• Prophylactic treatment
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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)
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Cells of the Immune SystemBone Marrow Stem Cells
Blood lineage
Red Blood Cells
Platelets
GranulocytesEosinophils, Neutrophils, Basophils
Monocytes
Macrophages
Lymphoid lineage (lymphocytes)
NK Cells
Pre-B Plasma cells
Memory B-cells
Pre-T(thymus)
T-helper cellsT-suppressor cells
Memory T cells
Cytotoxic T cells
Delayed hypersensitivity T cells
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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
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Some examples
• Smallpox
• Flu
• “Childhood diseases”– Measles, chickenpox
• Rotavirus
• Bacterial diseases ?– Tetanus– Anthrax
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Routes of Transmission
• Person-to-person: Physical contact• Indirect person-to-person
– Aerosol– Fomites
• Vehicle-borne– Food, water
• Vector-borne– Insects
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Vector-borne cycle of infection
• Disease agent is a microorganism
• Reproduces in a reservoir or host
• Is transmitted by a vector
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Vector-borne cycle of infectionExample: West Nile
Flavivirus
Disease agentTarget organisms Reservoirs
?Vector
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Vector control
• Vector-borne diseases– E.g. West Nile, malaria
• Identify vectors, reservoirs– Information on vector life-cycles
• Eradicate vectors, reservoirs– How ?
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Mosquitos
• Pesticides
• Larvaecides
• Malathion
• Naled (an OP)
• Synthetic pyrethroids
• Mosquito traps
• Drain water pools
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Insecticides
• Chlorinated hydrocarbons• Organophosphates• Carbamates
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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
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Is vaccination an option ?
• Vaccinate vectors ?
• Reservoirs ?
• Target species ?
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Attack disease agent directly
• Inside host – antibiotics ?
• In transmission media– Fumigation, sanitization, sterilization
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Disinfection
• Physical– Heat, pasteurize, autoclave– Time/temperature dependence
• Biological– Predation, competition
• Chemical– Destroy versus prevent reproduction
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Water disinfectants
• Chlorine
• Chlorine dioxide
• Chloramines
• Ozone
• UV light
• Effectiveness differs with type of organism
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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
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Chlorine Dioxide
• Weaker oxidizing agent
• More effective at higher pH
• Poor residual
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Chloramines
• Monochloramine, NH2Cl
• Need chlorine and ammonia gas, generated on-site
• Weaker oxidizing agent
• Fewer THMs
• Less offensive taste/odor
• Poor residual
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Ozone
• O3
• Generated on-site
• Strong oxidizing agent
• Effective against Giardia
• Odor/taste not offensive
• Poorly water-soluble, no residual
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Ultra-violet light• UVA, UVB, UVC
• Attacks nucleic acids
• Less effective in opaque/colored waters
• No residual
100 290 320 400 nmUVAUVBUVC
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Physical Hazards
• Heat• Cold• Trauma
• Radiation– Ionizing radiation
(radioactivity)– Non-ionizing radiation
• X-rays• UV• Infrared• Microwave• Radio• Electromagnetic