510 likes | 929 Vues
3rd MICROBIOLOGY SEMINAR. Sanitary Microbiology. Current issues facing the developed and developing world. Dr Gavin Collins Microbial Ecology Lab (3783) Environmental Change Institute (5047). Sanitary Microbiology. WATER…. … is responsible for, by some estimates, approximately. 80%.
E N D
3rd MICROBIOLOGY SEMINAR Sanitary Microbiology Current issues facing the developed and developing world Dr Gavin Collins Microbial Ecology Lab (3783) Environmental Change Institute (5047)
Sanitary Microbiology WATER… … is responsible for, by some estimates, approximately 80% of all infectious disease - not just waterborne diseases, but any disease where water plays a role… WATER ASSOCIATED DISEASES
There are waterborne diseases, such as cholera, typhoid, bacillary dysentery, infectious hepatitis; 1 Water-washeddiseases, such as trachoma, scabies, dysentery, louse-borne fever; 2 Water-based diseases, such as schistosomiasis, and Guinea worm; 3 And water-related diseases (involving an insect vector) such as malaria, sleeping sickness, or onchocerciasis. 4
H2O can act as a vector for the transmission of bacterial, viral and protozoan agents which cause a variety of diseases (mainly intestinal) It can also be linked to worm invasions and viral/protozoan diseases transmitted by insects (aquatic hosts or insect breeding in H2O - indirect) Water-associated diseases can be classified under 4 different categories: -
1. Water-borne diseases Mainly enteric diseases resulting from the ingestion of faecally-contaminated H2O (man, animal and bird excreta) In developed countries, classical H2O -borne diseases are mostly low infective dose infections - cholera and typhoid fever (rare), leptospirosis (rare); viral infections; Campylobacter (bacterium) and Giardia and Cryptosporidium (protozoa) infections - becoming more common in Ireland
In developing countries (or as a result of the breakdown of sanitary services in developed countries - earthquakes, war etc.), a variety of other, high-infective dose diseases can be transmitted via H2O - infectious hepatitis, Vibrio (bacterial) infections; bacillary dysentery; other viral infections etc. (human and/or animal origin All water borne diseases can also be transmitted by other routes that permit ingestion of faecal matter - e.g. contaminated food
2. Water-washed diseases • Diseases linked to H20 scarcity and resultant poor personal hygiene • Obviously more common in tropical, 3rd world countries where H2O supplies may be scarce • Intestinal and non-intestinal infections • Intestinal: Shigella (dysentery); typhoid; cholera; Campylobacter; Giardia; Cryptosporidium; viruses
Non-intestinal: Infections of the skin and mucous membranes - bacterial skin sepsis; scabies; fungal infections such as ring-worm; fungal mouth ulcers etc.
3. Water-based diseases • Diseases caused by pathogens that have a complex life-cycle which involves an intermediate aquatic host • All of these diseases are caused by worms, e.g. Schistosomiasis caused by the Schistosoma worm which uses aquatic snails as an intermediate host, also the Guinea worm (Dracunculus medimensis) which uses a small crustacean as an intermediate host
4. Water-related diseases Diseases caused by pathogens carried by insects that live near H2O and act as mechanical vectors Very difficult to control and diseases are very severe
Examples: • Yellow fever (viral disease) is transmitted by the mosquito Aedes spp.; • Dengue (viral) carried by the mosquito Aedes aegypti (breeds in water); • Malaria is caused by a protozoan (Plasmodium spp.) and is also spread by a mosquito (Anopheles spp.); • Trypanosomiasis (Gambian sleeping sickness) is also caused by a protozoan transmitted by the riverine Tetse fly (Glossina spp.)
Increasing Crises Worldwide Population growth Pollution with increased flooding leads to breakdown of sanitary infrastructure and further spread of disease Climate change Engineered systems (such as water treatment and distribution systems) Population susceptibility (increasing numbers of elderly & immuno-suppressed people)
Methane (CH4) from anaerobic digestion Greenhouse effect Bovine generated CH4 CO2 from industry ANAEROBIC DIGESTION Urbanisation Complex molecules Globalisation Simpler molecules Biogas (CH4 & CO2) Celtic Tiger economy Wealth & Wastefulness Kyoto treaty
The diseases that result from flooding vary according to geographic region. Typical ones include cholera, typhoid, dengue, Rift Valley fever, malaria, hepatitis A, AGI [acute gastro-intestinal illness], and ARI [acute respiratory illness]. Flooding
Problems involved in getting clean, safe water to people in the developing world • Water supplies in communities highly susceptible to municipal, agricultural, and industrial contamination. • e.g., in India, huge numbers of people live in slums sited in low-lying points, and at end-of-pipe sites.
CASE STUDY Hyderabad, India • Water has maximum "residence time" in deteriorating distribution systems. Uses antiquated British water treatment technology designed for a much smaller population, only supplies water for 2 hours per day. The remaining time, 22 hours per day, water sits stagnant in the distribution system. In addition to pathogens in drinking water, slums tend to be sited near standing water.
Moreover, children routinely play in this water - both fouling it and further exposing themselves to disease. Standing water is a major problem in malaria and other vector-borne diseases. Cholera, giardiasis, hepatitis, shigellosis, typhoid, and AGI Other infections such as legionellosis, cryptosporidiosis, and mycobacterial infections occur, but are seldom diagnosed.
Absence of Sanitary Infrastructure Often in the developing world gastroenteritis and other infections cause unnecessary mortality • e.g. Massai in Kenya each year the current infant mortality rate is 20% for children < 5 years old from diarrhoeal infections - Campylobacter/E. coli
Treatment for these infections does not need expensive drugs or antibiotics (self-limiting infections) • Needs only water and salt to balance loss - but if available water is contaminated?? • Diarrhoea kills 15000 < 5 year olds every day, 5.5m/annum • Treatable at the cost of <10 cent per child
WBD’s in a developed world context • Growing problem in Ireland primarily due to deterioration of ground and surface water quality • Massive volume of wastes produced in intensive agriculture can contaminate a water supply if not managed correctly
General causes of WBDOs include: 1) No treatment 2) Breakthrough at treatment plant 3) No disinfectant residual 4) Direct sewage contamination through pipe leakage, breakage, back-siphoning, and cross-connections
Where the problems arise Corrosion of pipe networks allowing contamination during distribution 30% of rivers polluted; 50% of group water supplies contaminated with E. coli formation leads to: Biofilm • biofouling; • foul odour, smell, colour, and the general impression of "dirty water”; • biocorrosion; • survival and proliferation of pathogens; disinfection resistance; • transfer of antibiotic and virulence factors
Problems with Microbiological Monitoring Current indicator organisms may not be adequate for the following reasons: The presence of coliforms in water only reflects sewage contamination - not potential pathogens like Legionella Coliform behaviour and die-off is not comparable to the behaviour of viruses and protozoa Die-off rates of faecal coliforms have been demonstrated to vary enormously
Problems with Microbiological Methods (cont’d) Techniques used to identify indicators rely on growth and culture - many organisms can be viable in the environment but unculturable using current methods(‘Plate-count anomaly’) Molecular methods based on DNA probes and PCR still not adequate
Challenges for the future: controlling Legionella and other organisms Legionella pneumophila an emerging pathogen - first recognized in the 1970s Example of how creation of a unique environment in our water systems that has lead to a "new" or newly recognized disease. Incidence of Legionnaires' disease in the U.S.: approximately 1,000 cases annually Estimated that over 25,000 cases of the illness occur each year, causing more than 4,000 deaths.
Legionella is one of the top three causes of sporadic, community-acquired pneumonia. Difficult to distinguish, many cases go unreported. For growth Legionella requires the following: stagnation; temps between 20° and 50°C (optimal growth range is 35° - 46°C); pH between 5.0 and 8.5; Microbes incl algae, flavobacteria, and Pseudomonas, which supply essential nutrients or harbor the organism (protozoa)
Optimal conditions created for Legionella growth in many modern buildings: Domestic hot-water systems with water heaters that operate below 60°C; centralized hot water systems [common in eastern European countries] Cooling towers, and fluid coolers that use evaporation; humidifiers and decorative fountains that create a water spray; spas and whirlpools.
Giardia and Cryptosporidium Protozoa and common causes of GI infections Used to be rare in Ireland, incidence now increasing Form oocysts as part of the life-cycle These oocysts are resistant to chlorination which is the only method used to disinfect water in Ireland
No detection methods for these organisms at the moment Use of conventional indicators meaningless How many of the 350,000 cases of food/water borne illnesses in Ireland last year caused by these organisms??
Conclusions • Partial solutions to the problems of maintaining clean safe water for all include: 1. Active surveillance 2. Population surveys 3. Low-cost solutions to treatment 4. Waste-water reclamation
5. Appropriate valuation of the resource 6. Assessments of impacts of engineered "ecosystems” 7. Monitoring of antibiotic resistance and changing virulence • Tighter regulation guided by precautionary principles
Further Info http://www.doh.ie/ http://www.who.int http://www.cdc.gov/health/ http://www.cfsan.fda.gov/~mow/intro.html http://www.epa.ie/ http://www.aem.org