Climate change and Climate change and microbial risk:microbial risk:

Observations from Observations from AustraliaAustralia

Dr David CunliffeDr David CunliffePrincipal Water Quality Adviser Principal Water Quality Adviser

SA HealthSA Health

EventsEvents

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 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 factorsAssociated 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 systemo 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 Cases studies

Milwaukee 1993o 403,000 cases of Cryptospordiosiso preceded by heavy spring rains and stormwater run-offo contamination of source water overwhelmed the filtration sysytem o led to changes in filtered water turbidity regulations

Walkerton 2000o 2300 illnesses and 7 deaths from Campylobacter, E.coli 0157o Preceded by heavy spring rain washing cattle manure into a groundwater

supplyo System poorly treated and managed

Sydney 1998o 3 boil water notices over several weekso heavy rain in catchment increased turbidity and washed livestock waste

into source waters. o contamination attributed to Cryptosporidium

High temperaturesHigh 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 Case study – Naegleria fowlerifowleri

Naegleria fowleri:o causative agent of primary amoebic meningitis (rare but almost always

fatal)o exposure requires forcing water into the nasal passageso naturally occurring amoeba with a resistant cyst stageo 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 - Case study - CryptosporidiumCryptosporidium

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 of Cryptosporidium infection by day of onset1/1/2007 to 21/4/2007

02

46

810

1214

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

Cases

Cryptosporidium infections by age group and sex

0

10

20

30

40

50

60

0..4 10..14 20..24 30..34 40..44 50..54 60..64 70..74 80+

Age group & sex

numb

er of

notifi

cation

s

MALES

FEMALES

Waterborne transmission ?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 - cyanobacteriaCase 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 growtho 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

SummarySummary 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 supplieso public education and health promotion