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EpidemiologyEpidemiology• Study of the distribution and Study of the distribution and
causes of disease in populationscauses of disease in populations– how many people or animals have a how many people or animals have a
diseasedisease– the outcome of the disease the outcome of the disease
(recovery, death, disability, etc.)(recovery, death, disability, etc.)– the factors that influence the the factors that influence the
distribution and outcome of the distribution and outcome of the diseasedisease
Epidemilogical TriadEpidemilogical TriadEnvironmentEnvironment
VectorVector
AgentAgent
HostHost
Types of HazardsTypes of Hazards•Biological HazardsBiological Hazards
–These are living organisms or their products that are harmful to humans
Biological HazardsBiological Hazards•Water-borne diseasesWater-borne diseases
– Transmitted in drinking waterTransmitted in drinking water•Disease organisms shed into Disease organisms shed into water in feceswater in feces
•Can produce illness in those who Can produce illness in those who consume untreated, contaminated consume untreated, contaminated waterwater
Biological HazardsBiological Hazards•Water-borne diseasesWater-borne diseases
– municipal water treatment municipal water treatment facilities are usually able to facilities are usually able to purify water purify water •removing these agents by removing these agents by filtrationfiltration
•killing them by disinfectionkilling them by disinfection
Biological HazardsBiological Hazards•Water-borne diseasesWater-borne diseases
– Examples Examples •Polio virusPolio virus•Hepatitis A virusHepatitis A virus•SalmonellaSalmonella•CholeraCholera
Waterborne Waterborne BacteriaBacteria
Escherichia coliBarbara E. Moore, Ph.D., Department of Biology, University of Texas at San Antonio
• Disease symptoms usually are Disease symptoms usually are explosive emissions from either explosive emissions from either end of the digestive tractend of the digestive tract
Waterborne Waterborne ProtozoansProtozoans
Giardia sp.**P. Darben
Barbara E. Moore, Ph.D., Department of Biology, University of Texas at San Antonio
• Disease symptoms are usually Disease symptoms are usually explosive emissions from either explosive emissions from either end of the digestive tractend of the digestive tract
Waterborne Waterborne Human Human VirusesViruses
Hepatitis A virus Hepatitis E virus
Norwalk virus* Rotavirus**F. Williams
Barbara E. Moore, Ph.D., Department of Biology, University of Texas at San Antonio
Eradicating Eradicating DracunculiasisDracunculiasis
Water and Sanitation – Critical Elements in Development - Mike Lee CSU @ HaywardWater and Sanitation – Critical Elements in Development - Mike Lee CSU @ Hayward
http://www.youtube.com/watch?v=Qwk-THcjmlI
http://www.youtube.com/watch?v=omudJzeX4q0&feature=related
http://www.youtube.com/watch?v=8FYgQFSrZDE&feature=related
Biological HazardsBiological Hazards•Food–borne diseasesFood–borne diseases
– To protect against food-borne To protect against food-borne diseasedisease•local health departments local health departments
– inspect inspect »food service establishments food service establishments (restaurants) (restaurants)
»retail food outlets (supermarkets)retail food outlets (supermarkets)»processing plantsprocessing plants
–verify that foodverify that food»stored stored »handled properlyhandled properly
Biological HazardsBiological Hazards•Food-borne diseasesFood-borne diseases
– Examples Examples •SalmonellaSalmonella
–Eggs or undercooked chickenEggs or undercooked chicken–ReptilesReptiles
•Escherichia coli 0157:H7Escherichia coli 0157:H7–SpinachSpinach–Undercooked meatUndercooked meat
»Jack in the BoxJack in the Box
Biological HazardsBiological Hazards•Vector-borne diseasesVector-borne diseases
– Transmitted by insects, Transmitted by insects, other arthropods and other arthropods and other animals including other animals including humanshumans
– Improper environmental Improper environmental management can cause management can cause vector-borne disease vector-borne disease outbreaksoutbreaks
Biological HazardsBiological Hazards•Vector-borne diseasesVector-borne diseases
– Examples Examples •MosquitoesMosquitoes
–MalariaMalaria–West Nile VirusWest Nile Virus
•FleasFleas–Bubonic plague Bubonic plague
3. Mosquito injects Plasmodium sporozoites into human host
2. Plasmodium develops in mosquito
1. Female mosquito bites infected human, ingesting blood that contains Plasmodium gametocytes
4. Parasite invades blood cells, causing malaria and making infected person a new reservoir
Anopheles mosquito (vector)in aquatic breeding area
eggslarva
pupaadult
Fig. 16.10, p. 409
Areas in which malaria hasdisappeared, been eradicated,or never existed
Areas with limited risk
Areas where malariaTransmission occurs
Biological HazardsBiological Hazards•Vector-borne diseasesVector-borne diseases
– Examples Examples •HumansHumans
–SARSSARS–Tuberculosis Tuberculosis –HIVHIV–STDsSTDs
Deaths per100,000 people
<2.5
2.5-10
10-35
35-70
70-100
100+
Tuberculosis epidemic, kills about 2 million people a year.
Biological HazardsBiological Hazards•Vector-borne diseasesVector-borne diseases
– Greatest viral health Greatest viral health threat to human life are threat to human life are virulent flu strainvirulent flu strain•1918 Swine Flu1918 Swine Flu
–Killed 20 – 30 millionKilled 20 – 30 million•Today flu kills Today flu kills
–1 million per year worldwide1 million per year worldwide–20,000 in the U.S.20,000 in the U.S.
Spread of DiseasesSpread of Diseases• Increases international travelIncreases international travel• Hunger and malnutritionHunger and malnutrition• Accidental introduction of insect Accidental introduction of insect
vectorsvectors• FloodingFlooding
Reducing Spread of Reducing Spread of DiseasesDiseases
• Reduce poverty and malnutritionReduce poverty and malnutrition• Improve drinking waterImprove drinking water• Reduce unnecessary use of antibioticsReduce unnecessary use of antibiotics• Educate people on taking antibioticsEducate people on taking antibiotics• Reduce antibiotic use in livestockReduce antibiotic use in livestock• Careful hand washing by medical staffCareful hand washing by medical staff
Hazardous Hazardous ChemicalsChemicals
•Methods to determine threatMethods to determine threat– Case StudiesCase Studies
•MD with actual patient recordMD with actual patient record– EpidemiologyEpidemiology
•Health officials investigating case Health officials investigating case studies studies
–Laboratory InvestigationsLaboratory Investigations•Substances that are fatal to more Substances that are fatal to more than 50% of the test animals (LD50) than 50% of the test animals (LD50) at a given concentrationat a given concentration
ToxicityToxicityToxicity LD50 Lethal Dose Examples
Super < 0.01 less than 1 drop dioxin, botulism
Extreme <5 less than 7 drops heroin, nicotine
Very 5-50 7 drops to 1 tsp. morphine, codeine
Toxic 50-500 1 tsp. DDT, H2SO4, Caffeine
Moderate 500-5K 1 oz.-1 pt. aspirin, wood alcohol
Slightly 5K-15K 1 pt. ethyl alcohol, soaps
Non-Toxic >15K >1qt. water, table sugar
(LD50 measured in mg/kg of body weight)
Dose-Response Dose-Response CurvesCurves
Nonlineardose-response
Lineardose-response
Thresholdlevel
Eff
ect
Eff
ect
DoseDose
Nonlineardose-response
Lineardose-response
No thresholdNo threshold
Eff
ect
Eff
ect
ThresholdThreshold
DoseDose
Fig. 16.6, p. 401
Chemical HazardsChemical Hazards•Hazardous ChemicalsHazardous Chemicals
•MutagensMutagens– Chemicals (and ionizing Chemicals (and ionizing
radiation) that changes DNA or radiation) that changes DNA or RNA in cellsRNA in cells
Chemical HazardsChemical Hazards•Hazardous ChemicalsHazardous Chemicals•MutagensMutagens
–TeratogensTeratogens•Chemicals, radiation, or viruses Chemicals, radiation, or viruses that cause birth defects while the that cause birth defects while the human embryo is gestating, human embryo is gestating, especially in the first three monthsespecially in the first three months
TeratogensTeratogens•Examples:Examples:
– RubellaRubella– Mercury in waterMercury in water– Fetal alcohol syndromeFetal alcohol syndrome– Crack found in babiesCrack found in babies– MethamphetamineMethamphetamine
Chemical HazardsChemical Hazards•Hazardous ChemicalsHazardous Chemicals•MutagensMutagens
– TeratogensTeratogens
–CarcinogensCarcinogens
CarcinogensCarcinogens•Causative agentsCausative agents
– Chemicals – Tobacco smokeChemicals – Tobacco smoke– Radiation – Pilots and cosmic Radiation – Pilots and cosmic
radiationradiation– Viruses – HPV and cervical cancerViruses – HPV and cervical cancer
•Promote growth of malignant Promote growth of malignant tumorstumors
CarcinogensCarcinogens•Latent PeriodLatent Period
– Long time lapse between Long time lapse between exposureexposure•SmokingSmoking•EatingEating•Lifestyle choices – laying in sunLifestyle choices – laying in sun
– SymptomsSymptoms•Lung cancerLung cancer•MelanomaMelanoma
Chemical HazardsChemical Hazards•Hazardous ChemicalsHazardous Chemicals•MutagensMutagens
– TeratogensTeratogens– CarcinogensCarcinogens
•Hormonally Active Hormonally Active AgentsAgents
Hormonally Active Hormonally Active AgentsAgents
•Estrogen-like chemicalsEstrogen-like chemicals– Alter developmentAlter development
•Early pubescenceEarly pubescence•Low sperm countLow sperm count•Runts in wildlifeRunts in wildlife
– Examples of hormone mimicsExamples of hormone mimics•BPABPA•Organophosphates pesticidesOrganophosphates pesticides•Industrial solventsIndustrial solvents
Precautionary Precautionary PrinciplePrinciple
•BioaccumulationBioaccumulation–An increase in An increase in concentration of a concentration of a chemicals in specific chemicals in specific organs or tissues in organs or tissues in organisms organisms
Precautionary Precautionary PrinciplePrinciple
•BiomagnificationBiomagnification– Increase in concentration in Increase in concentration in organismsorganisms•DDTDDT•PCBPCB•Slowly degradable, fat-soluble Slowly degradable, fat-soluble chemicalschemicals
– At successively higher trophic At successively higher trophic levels of food chains or in fatty levels of food chains or in fatty tissuetissue
DDT in fish-eatingDDT in fish-eatingbirds (ospreys)birds (ospreys)
25 ppm25 ppm
DDT in largeDDT in largefish (needle fish)fish (needle fish)2 ppm2 ppm
DDT in smallDDT in smallfish (minnows)fish (minnows)0.5 ppm0.5 ppm
DDT inDDT inzooplanktonzooplankton0.04 ppm0.04 ppm
DDT in waterDDT in water0.000003 ppm,0.000003 ppm,Or 3 ppmOr 3 ppm