Risk to public health associated with private water supplies Dr - - PowerPoint PPT Presentation

Risk to public health associated with private water supplies

Dr Emmanuel Okpo

Private Water Supply Workshop October 2013

Outline

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

Grampian

Private water Quality Standards

The Private Water Supply (Scotland) regulations 2006 ‘…. 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’ Drinking Water Directive 98/83/EC

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

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

Sources of contamination

• Direct or indirect faecal contamination
• Domestic and farm animals-defecating in
• r 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

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)

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

Health Risks

Pathogens Definition & Health effect E Coli O157

• 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 109 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

Health Risks

Pathogens 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.

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

• 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

Nitrate

• 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.

Waterborne outbreaks

• Scotland 1945 – 1987 (Benton et al 1989)

– 57 waterborne outbreaks – 21 (37%) private supplies affecting 9362 people (Lamb et al 1998)

More recently ………

Year Organism Location Total ill Total ill and positive Source 2008 E.coli O157 Private houses 15 12 PWS 2008 E.coli O157 & Non O157 E.coli Farm 3 2 PWS 2010 E.coli O157 Holiday accommodation 15 10 PWS 2012 Campylobacter & Cryptosporidium Hospital 27 3 PWS

Source: ObSurv - Health Protection Scotland 2013

Outbreaks of Infectious Intestinal Disease (Main mode of transmission- ‘waterborne’) 2008-2012

.

Locking M. et al 2010. Private water supplies in Scotland- Still an important source of E Coli O157 outbreak?

An Outbreak of E.coli O157 infection in Aberdeenshire

The Setting

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 11000 properties

• 3 Others on PWS with similar illness

identified and interviewed

Monday 25 August

• All households on PWS interviewed except 1
• 2 further positive cases notified by ARI Labs
• Outbreak declared
• OCT convened

Epidemiology

• 30 residents in 8 properties

– 16 male, 14 female – 11 = age <16 – 15 symptomatic – 6 male (15 – 60) – 9 female (5 – 42) – 5 = age <16

1 2 3 8 . 8 . 8 9 . 8 . 8 1 . 8 . 8 1 1 . 8 . 8 1 2 . 8 . 8 1 3 . 8 . 8 1 4 . 8 . 8 1 5 . 8 . 8 1 6 . 8 . 8 1 7 . 8 . 8 1 8 . 8 . 8 1 9 . 8 . 8 2 . 8 . 8 2 1 . 8 . 8 2 2 . 8 . 8 2 3 . 8 . 8 2 4 . 8 . 8 2 5 . 8 . 8

1 2 3 4 5 6 7 0-4 5-9 10- 14 15- 19 20- 24 25- 29 30- 34 35- 39 40- 44 45- 49 50- 54 55- 59 60- 64

• No. in age group

Epidemiological investigation

15 symptomatic 15 asymptomatic 3 symptomatic E.Coli O157 -ve 12 symptomatic E.Coli O157 +ve 3 asymptomatic E.Coli O157 +ve 12 asymptomatic E.Coli O157 -ve 15 symptomatic 15 asymptomatic 15 cases E.coli O157

All isolates E.coli O157 phage type 32 - indistinguishable

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

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

Water Supply

Environmental Investigation

Borehole Animal trough Animal trough Houses

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

Animal trough - adjacent

Storage tank

Animal trough – new Borehole 1 3 4 2

Environmental Investigation

Results

Environmental 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

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

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

Thank you for listening