Transcript ppt
3.2 Environmental transmission of pathogens Learning objective: to become familiar with environmental transmission routes for pathogens, especially in relation to water and sanitation. Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Infectious disease outbreak among 100 persons Interviews showed that all had eaten e.g. raw lettuce What brought EHEC to the lake? Grass on the grazing fields had EHEC Why were the cows not sick? From where did this At the lab: these bacteria strain come? EHEC bacteria were also found in samples of irrigation water At the lab: isolation of bacteria - and also in a stream in the patients stool and proved to be the same- EHEC! Cows were infected, but without symptoms From where did cows get infected by EHEC? 100 persons in a small community were affected by severe diarrhoea, ten of whom were hospitalised etcetera Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden : An example of zoonosis i.e. transmission from-animal-to-human 3. Irrigation of lettuces (no requirement for analysis of the water) 1. Run-off from agricultural land grazed by cattle infected with EHEC 4. The lettuce was consumed by a large number of individuals – resulted in 100 cases (some 10 hospitalised) 2. Manure runoff to river water At the lab: isolating and comparing bacteria in samples from patients and in water samples Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Transmission by animals Zoonoses Transmission humans animals May cause symptoms or not in animal Vectors Insects, rodents, birds – mechanical transport Birds, wild and domestic animals infected without symptoms Intermediate host Animal necessary for lifecycle of pathogen, e.g. malaria, schistosomiasis Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Features of excreta hygiene Microorganisms in -excreta Urine Sterile in body Naturally containing some bacteria after excretion Few diseases transmitted by urine Low risk to handle Faeces Naturally containing high amounts of bacteria Many diseases transmitted by faeces (faecal-oral) May contain pathogenic bacteria, viruses, protozoa or helminths Significant risk to handle Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden The ”F-diagram” - main routes for the spread of diarrhoea (Esrey et al. 1998) Transmission routes for pathogens in human excreta Excreta from humans & animals 1 Land Runoff 3 Sewage 2 Solid Waste 4 Landfills Oceans and Estuaries 5 Rivers and Lakes 6 Groundwater 7 Shellfish 8 Recreation 9 10 Water Supply Crops Irrigation 11 12 Aerosols 13 Humans Adapted from Gerba et al. 1975 Pathogens in faeces May contain bacteria, viruses, parasitic protozoa and helminths that cause infections Diarrhoeal disease is the main concern Faeces should be considered a health hazard Need to be treated before use as a fertiliser Easier to handle and treat if diverted from other waste fractions Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Sources of faecal indicator bacteria Origin Birds and other animals Agricultural runoff and effluent Recreational use Domestic sewage Industrial effluent Stormwater and surface water Leachate Sea Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Microorganisms in urine Urine is sterile in the bladder Freshly excreted urine contains <10 000 bacteria/ml Urinary tract infections - not transmitted through the environment Leptospira interrogans - low prevalence Salmonella typhi, Salmonella paratyphi - developing countries, faecal-oral transmission more common Schistosoma haematobium - fresh water snail needed for development low risk for transmission of infectious diseases through urine Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Origin of pathogens in wastewater - contribution from different waste fractions Faeces Urine e.g. laundry, washing diapers, from food stuffs Industry only a few diseases transmitted through urine Greywater the main source of pathogens that cause enteric infections abattoir, food industry (plant pathogens) Storm water e.g. surface run-off – animal faeces Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Ecological Alternatives in Sanitation Contamination of groundwater Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Contamination of drinking water Drinking water quality Contaminated surface- or groundwater Wastewater outlet, latrines, run-off Contamination during distribution Heterotrophic bacteria, E. coli, metals, nitrate (other aspects are smell, colour) Growth in pipes, intrusion of wastewater Contamination of finished water During storage and handling, e.g. reservoirs, vendors Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Health risks related to untreated wastewater Local environmental pollution High risk of down-stream pollution Exposure from e.g. swimming and intended household use Pollution of drinking water sources Accidental exposure Surface run-off and ground water infiltration Contamination of irrigated crops Exposure during irrigation and at consumption Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Excretion of pathogens in faeces Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Pathogens in urine and importance of urine as a transmission route Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Pathogens in mixed wastewater Small volumes of faeces contaminates large volumes of clean water Collection from a large number of persons – pathogens continuously present Smaller systems – higher concentration of a specific pathogen Treatment not optimized for killing pathogens 10% of wastewater is treated (developing countries) 20 million ha (?) irrigated with wastewater Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Pathogens in greywater Lower concentrations of pathogens here than in faeces Faecal origin of pathogens (bathroom and laundry) Pathogens from food stuffs (kitchen sink) Shower and bath, washing clothes, washing diapers Faecally contaminated vegetables (e.g. from irrigation with wastewater or application of animal manure), soil Contaminated meat (e.g. chicken) Health risk from disposal or reuse Contamination of nearby surroundings Contamination of drinking and recreational water Irrigation of crops Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Typical concentrations of microorganisms in sludge (EC, 2001) [per g wet weight] Bacteria 6 E. coli 10 Salmonella 10 -10 Virus Enterovirus 10 -10 Protozoa Giardia 10 -10 Helminths Ascaris 10 -10 Toxocara 10-10 Taenia 5 2 3 2 4 2 3 2 3 2 When treating wastewater, pathogens are being concentrated in the sludge – not in the effluent Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Possible transmission routes for pathogens from organic fertilisers (e.g. faeces) Handling on site • The handling and reuse of all types of waste products with human or animal origin involve hygienic risks Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Contamination of food Contaminated seeds, uptake of pathogens? Organic fertilisers – human excreta, wastewater, animal manure Irrigation – wastewater, contaminated surface water Handling and storage Cooking Storing of cooked food, growth of pathogens Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden Waterborne diseases and sanitation Waterborne diseases are caused by: - ingestion of water contaminated by human or animal faeces or urine containing pathogenic bacteria or viruses. - they include cholera, typhoid, amoebic and bacillary dysentery and other diarrhoeal diseases. Sanitation system that involve reuse need to prevent disease transmission, mainly by: - protecting ground- and surface water - safe handling and use of the waste products in agriculture Caroline Schönning, Swedish Institute for Communicable Disease Control, Solna, Sweden