Presentation on theme: "Chapter 3. Sanitation and public health"— Presentation transcript:
1Chapter 3. Sanitation and public health What happens in me if I am exposed(different pathogens)Can wemanage therisks?Which are the healthTargets and guidelineProcedures?Cases and participatoryApproaches on differentCommunity levels!How am Iexposed?From where dopathogen come?How can treatmentand interventionsminimizetransmission?Caroline Schönning, Swedish Institute for Infectious Disease Control (SMI), Sweden
23.1 Exposure and effects in humans How are infectious diseases transmitted?What happens when people are exposed to pathogens?Learning objective: To know and be familiar with pathogens of concern in water and sanitation systems, including the symptoms they cause and the effect on the individuals/population
3DALYs – a general measure for health The Global Burden of Disease (GBD)Murray and Lopez, 1996Disability Adjusted Life Years (DALY)morbidity: years lived with a disabilitymortality: years lostDALY (loss of healthy lived years) = n x t x Sn = number of affected personst = the duration of the health effectS = measure of the severity of the health effect (mortality = 1)
4Hypothetical example of DALYs Quality of life Index1.0Remaining“disability”Years lost0.8Acute(infectious)illness0.4Prematuredeath by 6520406080Age
5Leading DALYs in in the world 1990 & 2020 Murray et al. (1996) Science 274:”The sanitary revolution” - the most important medical milestone since 1840 !? (BMJ, 2007)
6DALYs attributable to risk factors Water and sanitation causes a major part (9%) of GBD, that largely could be prevented. (WHO, 2008)
7PEM: protein-energy malnutrition Diseases contributing to the water-, sanitation- and hygiene-related disease burdenPEM: protein-energy malnutrition(Adapted from WHO, 2008)
8Global risk factors for disease and premature deaths (% of DALYs) Child underweigth for ageUnsafe water, sanitation, hygieneChild underweight ~7.9% Nutrition deficiencies ~7.4% Water & sanitation ~3.4% Total targeted by ”Ecosan”: ~18.6% in Sub-Saharan Africa ~7.6%854 million chronically hungry 2 billion without food security FAO, 2006Low fruit & vegetable intakeZinc deficiencyIron deficiency aaemiaVitamin A deficiencyRef: Lopez et al Global and regional burden of disease and risk factors; FAO, 2006
9Infectious diseasesFrequency of infection World´s most common – karies Commonly existing diarrhoea and food-poisoning Unusual opportunistic infections in immunocompromised individualsSymptoms None (e.g. polio) Mild diarrhoea (e.g. Staphylococcus food poisoning) Life-threatening loss of water and salts (e.g. cholera)
10The field of Epidemiology Definitions(1) The study of the relationships of the various factors determining the frequency and distribution of diseases in a human community.(2) The field of medicine that attempts to determine the exact causes of localized outbreaks of disease. (Ologies & -Isms. Copyright 2008 The Gale Group, Inc)The start in the middle of the 19th centuryCholera epidemics in London - consumption of water implied an increased risk for disease (John Snow)Established that germs or bacteria cause infectious disease (Pasteur, 1857)
11Occurrence of disease Prevalence Incidence The number of cases in a defined population at a specified point in timeIncidenceThe number of new cases arising in a given period in a specified population
12Transmission of infectious agents Direct transmissionTouchingKissingSexual intercourseOther contactAirborne, short distance via droplets, coughing, sneezingTransfusion (blood)TransplacentalIndirect transmissionVehicle-borne (contaminated food, water, towels, farm tools etc.)Vector-borne (insects, animals)Airborne, long distance via dust and dropletsParenteral (injections with contaminated syringes)
13Consequences of exposure No symptomsNo infectionExposureSymptoms of diseaseInfectionSusceptibleRecoveredDeathImmune
14Infectious dose Minimum infectious dose ID50 Probability of infection Dose-response curvesSeverity of disease depending onIngested doseThe condition of the mechanical barrierThe stability of the normal enteric floraImmunityThe nutritional status of the individual
15Immunity – vulnerable groups More vulnerable groups in the society The old (elderly)InfantsPregnant womenImmunocompromisedMalnourishedThese groups comprise about 20% of the general population and are growing
16Epidemiology - Definitions Pandemic: An epidemic (a sudden outbreak) that becomes very widespread and affects a whole region, a continent, or the world.By contrast:An epidemic affects more than the expected number of cases of disease occurring in a community or region during a given period of time.An endemic is present in a community at all times but in low frequency.(http://www.medterms.com/script/main/art.asp?articlekey=4751)
17Epidemic to endemic illnesses as detected by health surveillance Outbreak detectedThreshold for detection for an outbreakNumber of CasesUndetected outbreakSporadicEndemic rateHyperendemicTime
18Diarrhoea and sanitation 4.1% of the total DALY88% of the burden attributable to unsafe water supply, sanitation and hygieneImproved sanitation can reduce diarrhoea by ~32%391 million cases averted if MDG target metCauses ~1/5 of deaths in children <5 years (1.5 million)Has decreased, in 1980´s estimated 2/3 of deathsLess significant decrease in diarrhoeal disease in low-income countriesInfections related to water and sanitationDiarrhoea causes ~1/5 of deaths in children <5 years (1.8 million). It has decreased, in 1980´s estimated to account for 2/3 of deaths, but there has not been a significant decrease in diarrhoeal disease in low-income countries. Diarrhoeal disease alone amounts to an estimated 4.1 % of the total DALY global burden of disease and is responsible for the deaths of 1.8 million people every year (WHO, 2004). It was estimated that 88% of that burden is attributable tounsafe water supply, sanitation and hygiene and is mostly concentrated on children in developing countries.A significant amount of disease could be prevented especially in developing countries through better access to safe water supply, adequate sanitation facilities and better hygiene practices.
19Regional differences in average health burdens from diarrhoeal diseases Source: Our PlanetCurrent annual diarrhea cases in SSA:1.2 billion which lead to dead children, mostly under 5 years
20Treatment of diarrhoea Program in the 1980´s for rehydrating children – avoiding deathInfromation, campaigns by WHO, UNICEFDid not give the expected success – less use than anticipatedSymptoms are commonDo not visit a medical doctorStart treatment late or not at allWant antibiotics or medicine that stops diarrhoeaExample: Ceará in BrasilDeath from diarrhoea decreasesDecrease in incidence or better treatment?General improvement of livelihoode.g. water quality, sanitation, waste management, income, litearcy, health care, vaccinationNo single factor related to lower number of diarrhoea casesContinued studies of the real situation
21Diarrhoeal diseases – Outbreaks related to water and sanitation Cholera36 reported outbreaks from (WHO)Risk during flooding“Natural environmental” spreadTyphoid feverAlso endemicShigellosis
22Cholera epidemic Characteristics for cholera outbreaks Acute watery diarrhoea, very deadly without rapid treatmentAffects adults as much as children, especially informal caretakersHigh political profile : can be used as a political leverageCharacteristics for cholera outbreakshigh attack ratelow mortalityeconomic and social burdenFactors of spreaddensity of populationtransportation facilitiesliving conditionsenvironmental reservoirs
23“Psychological” impact Consequences of cholera outbreaksHealth Care Facilities overwhelmedMore supplies, more staffHealth impactCholera OutbreakSocial BurdenPanicMedia“Psychological” impactEconomic burdenPolitical impactWho is responsible?
24Classification of communicable diseases related to water and sanitation Water-borne diseases: caused by the ingestion of water contaminated by human or animal faeces or urine containing pathogenic bacteria or viruses or parasites; include cholera, typhoid, amoebic and bacillary dysentery and other diarrhoeal diseases.Water-washed diseases: caused by poor personal hygiene and skin or eye contact with contaminated water; include scabies, trachoma and flea, lice and tick-borne diseases.Water-based diseases: caused by parasites found in intermediate organisms living in water; include dracunculiasis, schistosomiasis and other helminths.(Other) Water-related diseases: caused by insect vectors which breed in water; include dengue, filariasis, malaria, onchocerciasis, trypanosomiasis and yellow fever.(WHO, 1996)24
25Waterborne pathogens – important in water and sanitation system BacteriaThe leading cause of gastrointestinal infections according to surveillance systemsSalmonella, Shigella, Campylobacter, E. coli (toxinprod.)EHECLegionellaOpportunistic e.g. Aeromonas hydrophilaVirusProbably the cause of many outbreaks, difficult to detectNoroviruses (Calici-, Norwalk like), rotavirus, hepatitis A
26Waterborne pathogens – important in water and sanitation system ProtozoaComplicated life cycles with resistent stages (chlorine)Giardia, Cryptosporidium, EntamoebaLow infectious doseMilwaukee (USA) 1993, individualsHelminths (worms)Varying transmission routes, e.g. soilborneAscaris, Trichuris, Schistosoma (bilharzia), hookwormA large problem in many developing countries
28Salmonella infection – Salmonellosis and Typhiod fever Salmonellosis – diarrhea, fever, and abdominal crampsCaused by a variety of serotypes, e.g. Salmonella Typhimurium and Salmonella EnteridisFoods contaminated with animal fecesAnimal origin (meat, poultry, eggs), vegetablesPets – handwashing importantParatyphoid and Typhoid fever - fever and other symptoms, life-threateningCaused by Salmonella TyphiContaminated food or waterMore common in areas with low sanitary standard
29Schistosoma Also known as bilharzia 200 million people are infected worldwideVariety of symptomsFreshwater contaminated by urine or faecesLife-cycle requires specific snail as host
30Viral gastroenteritis What is viral gastroenteritis?Inflammation of the stomach and small or large intestinesCaused by a variety of viruses that results in vomiting or diarrheaOften called ”stomach flu" (but not caused by the influenza viruses)What causes viral gastroenteritis?Many different virusesFor example: rotaviruses, adenoviruses, caliciviruses, astroviruses, Norwalk virus, and a group of Norwalk-like viruses (later called calicivirus, norovirus)
31RotavirusRotavirus is the most common cause of severe diarrhea among children Globally, rotavirus is estimated to cause 527,000 deaths in children annuallyVomiting and watery diarrhea for days, and fever and abdominal pain occur frequentlyImmunity after infection is incompleteVaccination possible but not widespread(http://www.cdc.gov/rotavirus)
32Norovirus Previously called calicivirus or Norwalk (Like) viruses TransmissionPerspn-to-personFood-borneWaterborne
33AscarisAscarisAscaris lumbricoides is one of the largest and most common parasites found in humansIt is estimated that 10% of the world's population is infected with this nematodeThe adult worms live in the small intestine and eggs are passed in the feces - a single female can produce up to 200,000 eggs each dayAscaris lumbricoides, fertilized egg. The egg is covered with a thick shell that appears lumpy approximate size = 65 µm in length.The adult worm. Adult females of this species can measure up to 18 inches long (males are generally shorter).
35Cryptosporidium Cryptosporidium is a small parasite, about 3-5 µm. It lives on the surface of the cells lining the small intestine and oocysts are passed in the feces. Transmission of the infection occurs via the oocysts. Many human infections have been traced to the contamination of drinking water with oocysts from agricultural "run-off" (i.e., drainage from pastures), so it is considered a zoonosis.
37GiardiaGiardia intestinalis (also known as Giardia lamblia or Giardia duodenalissoil, food, or water that has been contaminated with fecesCommon in both developing and developed areasGiardia lamblia trophozoites live in the small intestine of the host. Cysts, which are resistant to adverse environmental conditions, are passed in the feces of an infected host, and the next host is infected when it ingests cysts in food or water contaminated with feces.The trophozoites adhere closely to the lining of the small intestine, and in heavy infections much of the lining can be covered with trophozoites. The giardiasis symptoms range from none (in light infections) to severe, chronic diarrhea (in heavy infections).
38Features of some gastrointestinal infections (Westrell, 2004)
39Emerging pathogens Emerging diseases Zoonoses Climate change Newly recognized orIncreasing importanceZoonosesMany emerging pathogens of zoonotic originAnimal faeces contaminate waterClimate changeIncreased risks related to water and sanitationAffects food-production
40Protozoa and helminths in faecal material Faecal samples from 120 urine-diverting latrines in KwaZulu-Natal, South AfricaVarying features – water-filled to dry (normal)Analysing for presence of:parasitic protozoa Giardia and Cryptosporidiumhelminths Ascaris lumbricoides, Trichuris trichiura and Taenia sppPicture provided by Teddy Gounden(Trönnberg et al., 2010)
41Protozoa and helminths in faecal material Parasites54% positive for Giardia21% positive for CryptosporidiumHelminths59% Ascaris lumbricoides48% Trichuris trichiura18% Taenia sppIn 73% of the 120 household toilets, one or several types of helminths were foundPrevalence by family (at least one member infected)Supports theory of high prevalence in certain areasTreatment needed before use of faeces(Trönnberg et al., 2010)