Inaction ‘not an option’

Rural Water News Spring 2008
Assessing the Cryptosporidium Risk
The challenge facing the GWS sector
One of the biggest challenges
facing group water
schemes and local authorities
is identifying if their
supply is at risk of infection
by the parasitic organism
Cryptosporidium and, in
particular, if there is an
associated health risk.
The good news is that all of
the challenges we are currently
facing regarding the
potential risk of Cryptosporidium
have been faced
by others over the past 20
years. The question is, what
can we learn from their experiences?
Interestingly, the only
countries in the world that
have implemented mandatory
risk assessment and monitoring
for Cryptosporidium in
drinking water supplies are
countries that have suffered
major outbreaks – namely the
USA, Australia, New
Zealand, Japan and the UK.
Dr Colin Fricker
When researching these outbreaks
and the actions that
were taken, I discovered one
common remedial factor and
that factor was Dr Colin
Fricker.
Originally employed as
Head of Microbiology at
Thames Water in England –
during which time he advised
the Drinking Water
Inspectorate (through the
Standing Committee of
Analysts) and the United
States Environmental
Protection Agency on matters
pertaining to
Cryptosporidium detection –
Dr Fricker was appointed
Senior Scientific advisor to
the New South Wales Inquiry
into the Sydney water crisis
in 1998.
Since 1999 he has consulted
water providers and others on
In January, the EPA issued a Cryptosporidium risk
assessment pack to all local authorities, with a clear
message that immediate steps must be taken to protect
the security of drinking water supplies. Based
on the Scottish model of risk assessment, the EPA
acknowledges that this is less than perfect.
Welcoming the environmental agency’s focus on
this issue, Dr Malcolm Bell of Technopath provides
an alternative view on how risk assessment might be
addressed in the context of rural water supplies.
aspects of Cryptosporidium
including treatment, laboratory
testing and media relations
in Africa, Asia,
Australia, Europe and North
and South America.
It is hugely significant,
therefore, that Dr Fricker has
agreed to become involved as
part of a joint initiative
between Technopath and the
National Centre for
Freshwater Studies in DkIT
[see story on facing page].
The objective of this partnership
is to develop a model
of risk assessment suitable
for group water schemes.
Scottish model
For historic and geographical
reasons the Scottish model
for Cryptosporidium risk
assessment – developed to
determine the frequency at
which sampling should be
undertaken – was adopted in
Ireland and has since been
modified on several occasions.
However, it was never
intended to be a model of
health risk. In our opinion
there are still aspects to determination
of risk that are not
addressed by either the original
Scottish model, or any of
its modifications.
So what exactly is Cryptosporidium? It is a waterborne parasite (pictured
above with a green stain) that causes the disease cryptosporidiosis.
Symptoms of the disease are vomiting, diarrhea, abdominal cramps, and
fever usually lasting one to two weeks. In immuno-suppressed individuals,
the disease can be fatal. Chlorine disinfection will not kill it.
Several factors
In using risk assessment to
understand the level of risk,
several important factors
need to be considered.
First and foremost, the contribution
of contamination
from a variety of sources,
including both animal and
human faecal material, needs
to be assessed.
Where semi-quantitative
risk assessments are performed,
the relative risk associated
with the different
sources needs to be
addressed.
This should include a variety
of factors such as the amount
of faecal material produced,
the likelihood of oocysts that
are infectious for human
beings being present and the
“mobility” of the faecal
material.
Treatment plants
Assessment of treatment
plants is also of paramount
importance when developing
a risk-based approach to
dealing with water supplies.
It is simply not adequate to
determine the risk reduction
based upon the type of treatment
present.
The performance indicators
of treatment need to be considered
and any risk reduction for
treatment needs to assess how
well the plant is performing
and, in particular, the consistency
of performance. This is
often ignored in risk assessment
studies.
Source of contamination
Any approach to determining
the risk must take into
account the specific sources
of contamination and the
likelihood of that contamination
containing oocysts that
are infectious for humans.
Much of this information has
only become available in the
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