Transcript Water Quality – An Ounce of Prevention

Climate change and
microbial risk:
Observations from Australia
Dr David Cunliffe
Principal Water Quality Adviser
SA Health
Events
 Three types of climate driven events have been associated with
increased risk of waterborne disease:
o Extreme rain
o High temperature
o Changeable weather
 Evidence of increased risk in the absence of catastrophic failure
 Causes may be:
o direct, through consumption of contaminated drinking water
o direct through non-drinking exposure
o Indirect due to changes in behaviour
Heavy rainfall
 A recurring theme with drinking water outbreaks in intact systems is
the influence of heavy rain (or snow-melt).
 Outbreaks have been associated with a wide range of microbial
agents e.g. Cryptosporidium, Giardia, Toxoplasma Enteroviruses,
Norovirus, Hepatitis A, E.coli 0157, Campylobacter and Salmonella
 Analysis of acute gastroillness in Wisconsin, USA showed that
rainfall was associated with an 11% increase in acute gastrointestinal
illness (Drayna et al 2010)
 Analysis of outbreaks in the USA (1948-1994) showed that:
o 51% of outbreaks were preceded by rainfall events above the 90th%ile
o 68% were preceded by events above the 80th%ile
o surface water outbreaks associated with rainfall during the same month
o groundwater outbreaks associated with a 2 month lag
o Curriero et al (2001)
Associated factors
 Rainfall alone does not cause outbreaks – in the case of drinking
water contaminated water needs to get to consumers.
 Sources of organisms:
o sewage (viruses, protozoa, bacteria)
o livestock (protozoa and bacteria)
o native animals (incuding birds) (primarily bacteria but occasionally
organisms such as Toxoplasma, Cryptosporidium)
o naturally occurring organisms (e.g. Burkholderia pseudomallei)
 Entry to system
o surface water – across-land flow into waterbodies
o groundwater – across land flow directly into bore or transport through
aquifers from primary source
o treatment failure (lack of treatment, breakdown, incomplete)
o distribution system failure (ingress of sewage overflows, bird/small
animal faeces in storage tanks)
Cases studies
 Milwaukee 1993
o 403,000 cases of Cryptospordiosis
o preceded by heavy spring rains and stormwater run-off
o contamination of source water overwhelmed the filtration sysytem
o led to changes in filtered water turbidity regulations
 Walkerton 2000
o 2300 illnesses and 7 deaths from Campylobacter, E.coli 0157
o Preceded by heavy spring rain washing cattle manure into a groundwater
supply
o System poorly treated and managed
 Sydney 1998
o 3 boil water notices over several weeks
o heavy rain in catchment increased turbidity and washed livestock waste
into source waters.
o contamination attributed to Cryptosporidium
High temperatures
 Favours growth of naturally occurring pathogens and harmful
organisms e.g. Naegleria fowleri, Legionella, Cyanobacteria)
 High temperatures can change behaviours influencing the level of
risk
 Impacts can be exacerbated by drought
 Transmission can be through a number of routes including ingestion
and inhalation; secondary transmission could be exacerbated
Case study – Naegleria fowleri
 Naegleria fowleri:
o causative agent of primary amoebic meningitis (rare but almost always
fatal)
o exposure requires forcing water into the nasal passages
o naturally occurring amoeba with a resistant cyst stage
o infectious form is sensitive to chlorine and chloramines (preferred
choice).
 Water is the only known source of infection. Drinking water supplies
implicated as an initial source (to swimming pools, garden hoses etc)
 Organism is thermophilic and grows at temperatures to 45OC. Cases
in Australia typically associated with extended periods of air
temperatures exceeding 35OC
 Higher temperatures increase growth and threaten barriers
(persistent residual) and also likelihood of exposures (increased use
of hoses, swimming pools, paddling pools)
Case study - Cryptosporidium
 Often see increased cases of GI illness in summer e.g. Salmonella,
Campylobacter. Generally considered food-borne. A number of
factors including hygiene (i.e. water role)
 In the summer of 2007 Sth Australia recorded increased infections
with Salmonella, Campylobacter and Cryptosporidium
 The Cryptosporidium outbreak was unusual – not typically
associated with foodborne disease oubreaks.
 Outbreak in summer of 2007 (400 cases in 3-4 months compared to
typical annual rate of 100-120)
Cases
Cases of Cryptosporidium infection by day of onset
14
12
10
8
6
4
2
0
1/1/2007 to 21/4/2007
1/1/2007 13/1/2007 25/1/2007 6/2/2007 18/2/2007 2/3/2007 14/3/2007 26/3/2007 7/4/2007 19/4/2007
Day of Onset
Cryptosporidium infections by age group and sex
number of notifications
60
MALES
50
FEMALES
40
30
20
10
0
0..4
10..14
20..24
30..34
40..44
50..54
Age group & sex
60..64
70..74
80+
Waterborne transmission ?
 Drinking water not the source – cases supplied from many different
sources
 But water was involved
o A high proportion had used swimming pools (40%). About 60 pools
involved
o Many reports of multiple cases within families. A number of reports of
children sharing bathwater (for water saving)
o It was hot and there were reports of infected children using undisinfected
paddling pools with other children
o Paddling pools not being emptied regularly (water saving)
Case study - cyanobacteria
 Decreased water flows in surface water bodies and increased
temperatures can produce conditions that are favourable for growth
of cyanobacteria
 In the last 2-3 years (drought and high temperaures) there has beeen
evidence of changed patterns of growth
o blooms at different times of the year (two blooms in the River Murray late
in the summers of 2009 and 2010)
o changes in species. The subtropical/tropical species Cylindrospermopsis
is becoming more common in temperate Australia (Murray-Darling)
 Drought reduces the availability of alternative sources of water
Summary
 There is evidence that the impacts of climate change will provide
greater challenges to drinking water supplies and increase risk from
enteric pathogens (faecal organisms) and environmental organisms
(Naegleria, Burkholderia, cyanobacteria).
 Increased risks could be associated with direct impacts from
contaminated water or indirect impacts from compromised hygiene.
 In both cases there are multiple impacts that will influence outcomes.
These include:
o awareness of operators of water supplies
o management and treatment of water supplies
o public education and health promotion