Risk to public health associated with private water supplies. Dr Emmanuel Okpo

Transcription

1 Risk to public health associated with private water supplies Dr Emmanuel Okpo Private Water Supply Workshop October 2013

2 Outline Water quality standards/drivers Contaminants (pathogens, chemicals) Population at Risk Health Risk An example- E coli O157 outbreak in Grampian

3 Private water Quality Standards The Private Water Supply (Scotland) regulations 2006 Drinking Water Directive 98/83/EC. to protect human health from the adverse effect of any contamination of water intended for human consumption by ensuring that it is wholesome and clean

4 Other Quality drivers The Water Quality (Scotland) Regulations 2010 WHO Guidelines on Drinking Water Quality 4th edition E coli O157 Task Force Report 2001 To provide clean and wholesome water to rural communities in Scotland

5 Contaminants Quality of private supplies variable depending on the source Main contaminants: micro-organisms i.e. bacteria, protozoa, parasites and viruses (s) and Chemicals- Lead, Nitrates, Iron, Arsenic, manganese Pesticides & by products

6 Sources of contamination Direct or indirect faecal contamination Domestic and farm animals-defecating in or near watercourses Wildlife and humans Run off from agricultural land after slurry spreading or grazing Leakage of stored manure/pesticides Leakage or poorly functioning septic tanks Environment

7 Population affected Over 150,000 in Scotland Lots more on holiday campsites, Bed and Breakfast, holiday lets In 2012, 19,916 registered PWS (2,434-type A & 17,482 -Type B)- 39% in Aberdeenshire -7,676 registered PWS 32,000 people in Grampian Mostly in Aberdeenshire (13% of popln on PWS)

8 Risk to public health Contaminated water can cause severe illness & outbreak of diseases Illness -immediate/long term 10 x more likely to become ill (HPS) Children under 4X likely to suffer diarrhoea than others

9 Pathogens E Coli O157 Health Risks Definition & Health effect Some E coli harmless or cause mild disease Verocytotoxic E coli severe disease Diarrhoea, bloody diarrhoea, abdominal pain HUS, acute renal failure and death Very low infective dose Incubation period 2-5 days (1-14 days) Also O111, O26, O103, O145 Europe Cryptosporidium Single-celled protozoan parasite- C. parvum and C. hominis found in lakes and rivers -contaminated with sewage and animal waste. Low infective dose 10 oocysts- (Calves/ lambs-oocysts 10 9 oocysts/day) resistant to chlorine, can survive for months- Bacteria not good indicator Acute, self limiting GI illness up to 4 weeks Severe in immuno-compromised patients- Can be fatal Incubation period 7-10 days (1-28 days) Need physical barrier-filtration, coagulation, sedimentation

10 Pathogens Health Risks Definition & Health effect Campylobacter Commonest cause bacterial gastro-enteritis Low infective dose Diarrhoea, abdominal pain and vomiting Short lived illness but can be serious Reactive arthritis, Guillain-Barre and HUS Incubation period 2-5 days (1-10 days) Giardia Lamblia lives in the intestine of infected humans or animals found on surfaces or in soil, food, or water that has been contaminated with the faeces from infected humans or animals Cyst resistant to chlorine Need physical barrier e.g. filtration, sedimentation Low infectivity dose- GI illness Viruses (enteric) Intestine of infected humans or animals Polioviruses x3, coxsackieviruses, echoviruses, and other enteroviruses, Coxsackie A viruses, Coxsackie B viruses, echoviruses, Gastroenteritis -rotavirus and norovirus meningitis echovirus, myocarditis -Coxsackie B.

11 Health Risks Chemicals Definition & Health effect Lead Toxic metal, household plumbing-pipes, solder, fixtures and faucets (brass), and fittings- Soft water dissolves lead from pip Nitrate Infants and children- delays in physical or mental development deficits in attention span and learning abilities. Adults long term mainly kidney problems or high blood pressure Septic tank, animal manure, fertilizers, pesticides, erosion of natural deposits Babies & infants- Blue-baby syndrome Arsenic Erosion of natural deposit, runoff from industrial waste (glass/electronic) skin damage, problems with their circulatory system, increased risk of cancer.

12 Waterborne outbreaks Scotland (Benton et al 1989) 57 waterborne outbreaks 21 (37%) private supplies affecting 9362 people (Lamb et al 1998) More recently

13 . Outbreaks of Infectious Intestinal Disease (Main mode of transmission- waterborne ) Year Organism Location Total ill Total ill and positive Source 2008 E.coli O157 Private houses PWS 2008 E.coli O157 & Farm 3 2 PWS Non O157 E.coli 2010 E.coli O157 Holiday PWS 2012 Campylobacter & Cryptosporidium accommodation Hospital 27 3 PWS Source: ObSurv - Health Protection Scotland 2013

14 Locking M. et al Private water supplies in Scotland- Still an important source of E Coli O157 outbreak?

15 An Outbreak of E.coli O157 infection in Aberdeenshire

16 The Setting

17 Friday 22 August Case 1 notified and interviewed Private water supply Initially 10 households Eventually dropped to 8 households Aberdeenshire over 7500 supplies, serves more than properties 3 Others on PWS with similar illness identified and interviewed

18 Monday 25 August All households on PWS interviewed except 1 2 further positive cases notified by ARI Labs Outbreak declared OCT convened

19 No. in age group Epidemiology residents in 8 properties male, 14 female = age < symptomatic 2 6 male (15 60) 1 9 female (5 42) 5 = age <

20 Epidemiological investigation 15 symptomatic 15 asymptomatic 12 symptomatic E.Coli O157 +ve 3 asymptomatic E.Coli O157 +ve 15 symptomatic 15 cases E.coli O asymptomatic 3 symptomatic E.Coli O157 -ve 12 asymptomatic E.Coli O157 -ve All isolates E.coli O157 phage type 32 - indistinguishable

21 Control measures Boil notice issued on 22 August Case finding 9 households interviewed Human sampling started 22 August Infection control advice hand washing and environmental hygiene Exclusion in accordance with NHS Grampian Exclusion Policy total of 9 individuals excluded

22 Water Supply Borehole Good condition, well sealed & housed, pumps submerged 30 metres deep Storage tank stainless steel, good condition Mud & stagnant water around base No fencing around tank Cattle nearby Pipeline Wet areas but no leaks identified

23 Environmental Investigation Houses Animal trough Borehole Animal trough

24 Environmental Investigation 2 Animal trough - adjacent Borehole 1 Storage tank 4 3 Animal trough new 1. One way valve not working -? Backflow into borehole 2. Valve controlling water supply not functioning 3. Similar valve to no 2 4. No treatment before houses? Back flow into supply

25 Environmental results Results Kitchen tap - E.coli O157 phage type 32 Storage tank E.coli O157 phage type 32 Animal trough 2 E.coli O157 phage type 32 Animal trough 1 - E.coli O157 phage type 14 Borehole and samples around storage tank negative. Borehole negative X3 then positive suggesting ongoing faecal contamination from cattle in field PFGE human and animal E.coli O157 phage type 32 cultures indistinguishable

26 Improvements Storage tank & borehole fenced off Cattle troughs supplied from storage tank Faulty valves at troughs replaced Chlorinated X 2 8 point of entry ultraviolet filters for houses Relevant person given advice

27 Conclusion Outbreak of E.coli O157 infection epidemiologically, environmentally and microbiologically linked to contaminated private water supply Limited severity of disease but high attack rate seen Potentially preventable with risk assessment and treatment on supply Highlights the need for treatment on these water supplies Need to raise awareness of advice and financial assistance

28 Thank you for listening