Transcript Document

The epidemiology of E. coli O157 in Scotland – tip of
the iceberg?
Kevin Pollock
Health Protection Scotland
"to improve the health of the Scottish population
by providing the best possible information and
expert support to practitioners, policy-makers and
others on infectious and environmental hazards."
www.hps.scot.nhs.uk
Why am I here?
• Central Scotland E. coli O157 outbreak (1996)
– 512 cases (279 lab-confirmed)
– 34 cases of HUS
– 17 deaths
• E coli O157 Task Force report
• Creation of a surveillance system for E. coli O157
and HUS to include both children and adults
What is surveillance?
‘the ongoing systematic collection, analysis and
interpretation of appropriate data, and the timely
dissemination of the resultant information to those
who need to know’
adapted from: Langmuir AD. The surveillance of communicable
diseases of national importance. New England Journal of Medicine,
1963, vol 268, pp 182-192
Factors which affect surveillance
• Laboratory testing policies
• Notification vs reporting
– Anthrax vs Campylobacter
• Clinician bias to pathogens
• Enhanced surveillance
Epidemiology
“The study of the distribution and determinants of healthrelated states or events in specified populations and the
application of this study to control health problems”
1. Human disease does not occur at random
2. Human disease has causal and preventive factors that
can be identified through systematic investigation of
different populations or subgroups of individuals within a
population in different places or at different times
Laboratory Surveillance
Appears in
national surveillance
Organisms identified
Specimens sent
Cases presenting
Cases of illness
Cases of infection
Lab reports and under-ascertainment
The study of IID in England (1996) showed factor is:
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3.8 for salmonella
10.3 for campylobacter
22.5 for rotavirus
315 for norovirus
i.e.
if there were 1400 reported cases of norovirus in 2005
then Scotland experienced 315 x 1400 = 441,000
cases
E. coli O157
• Gram (-) rods, usually sorbitol-fermenting, part of the
VTEC family
• Reservoir – cattle/livestock/humans
• Can exist in a VBNC state – problems with detection
• Abdominal cramps, bloody diarrhoea, afebrile
• May develop into the haemolytic uraemic syndrome in
10-15% of cases resulting in kidney failure and possible
death
• Patients should not be treated with antibiotics
E.coli O157: NHS Board of
Reporting Laboratory 2007
Shetland 0.0
Orkney 15.4
Western Isles 0.0
0 - 2.5
Highland 0.9
2.6 - 5.0
> 5.0
Grampian 9.0
Tayside 3.6
Argyll & Clyde 4.6
Greater Glasgow 0.8
Lanarkshire 1.4
Ayrshire & Arran 3.8
Fife 2.0
Forth Valley 2.1
Lothian 2.8
Borders 8.2
Dumfries & Galloway 9.5
Scotland 3.4
E.coli O157: rates per 100,000 population 1984-2007
12
Cases per 100,000 population
10
Scotland
England & Wales
N Ireland
Ireland
8
6
4
2
0
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
Data from outwith Scotland courtesy of Health Protection Agency Belfast & London
and Health Protection Surveillance Centre Dublin (2007 figures are provisional)
2006
E. coli O157/HUS in children
E. coli O157/HUS in adults
Progression of E. coli O157 (VTEC)
Tarr et al. 2005, Lancet; 365: 1073-1086.
How important?
Of 200-300 reported cases per year in Scotland:
• ~ 2-3 die
• 80-85% are sporadic infections
• 70% have bloody diarrhoea
• 50% are admitted hospital
• 20% are in hospital for over a week
• 10-15% have HUS (20-35 cases)
• 90% of HUS cases are under 16
• Potential for devastating outbreaks…….
Recent selected outbreaks
• 1996, Scotland, butcher
– 512 cases, 17 deaths
• 1996, Japan, school meals
– 10,000 cases, 11 deaths
• 2000, Canada, mains water
– 1300 cases, 6 deaths
• 2005, Wales, school meals
– 158 cases, 1 death
The Microbiological Safety of Food
Part II 1991
“We see poultry and their
products as the most important
source of human gastrointestinal
infections arising from food.”
Spinach outbreak, USA, 2006
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Cases of E. coli O157 in 26 different states in USA reported
eating fresh spinach (95% of cases)
– 183 cases
– 92 hospitalised
– 29 had HUS
– 1 person died
E. coli O157 with a PFGE pattern matching the outbreak strain
isolated from three open packages of fresh spinach consumed
by cases (1 from New Mexico, 1 from Utah, and 1 from
Pennsylvania)
Spinach grown in California was implicated in the outbreak –
same strain found in feral swine nr spinach fields
Jay et al. Emerg Infect Dis. 2007 Dec;13(12):1908-11.
The power of PFGE
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Pulsed field gel electrophoresis
PulseNet
Standardized molecular sub-typing
(or “fingerprinting”) of foodborne
disease-causing bacteria
Allows for rapid comparison of
patterns and identifies foodborne
diseases early
Importance of stool testing and
food testing
Helps FSA identify areas where
implementation of new measures
are likely to increase the safety of
our food supply
Morrison’s outbreak, Paisley - 2007
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9 cases associated with meat delicatessen
All cases confirmed phage type 2
1 fatality - 66-year old female
No other cases associated with consumption of cold
cooked meats from Morrison’s UK-wide
• Hypothesis - cross-contamination of various cold cooked
meats at the particular delicatessen
• Fatal accident enquiry
Aberdeen outbreak, 2007
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9 confirmed cases associated with hotel and social club
1 case hospitalised
EHOs investigated kitchen and routines
Microbiological sampling of foodstuffs including cold
cooked meats, coleslaw, salad leaves
All samples negative for E. coli O157
7 out of 10 people from club consumed cold meat platter
Descriptive epidemiology estimates salad part of platter
as being suspect vehicle – previously washed in salted
water – now washed in disinfectant solution
PFGE not used hence descriptive
Unpasteurised cheese
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Precedent of Listeria in Lanark Blue
Are all unpasteurised cheeses labelled so?
Cheese boards in restaurants – labelling?
Cluster of cases of haemolytic uraemic
syndrome due to unpasteurised cheese
– Deschenes et al. (1996) Pediatr Nephrol, 10
How are the VTECs being transmitted?
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50% of cases unknown transmission
EHO reports of farm contact (p< 0.001)
EHO reports of person-person spread (p< 0.001)
Small no. of reports of food as source of infection
(pre-2007) – not statistically significant
• Private water supplies – theoretical but actual?
Haemolytic uraemic syndrome (HUS)
• Characterised by microangiopathic haemolytic
anaemia with red blood cell destruction and fever
• Variable neurological involvement
• Variable renal impairment
• Acute onset, often fatal and difficult to diagnose
• 85-90% cases associated with VTEC
Aims of ENSHURE
• Clinically driven system
• Combines info on short-term and long-term outcomes, clinical
management and treatment of HUS/TTP
• Provides data to enable future prevention and management
including
» Epidemiology
» Clinical parameters
» Social outcomes of infection
Clinical markers for HUS and TTP
Clinical markers
HUS
TTP
Significance
14 +/- 1.5
21 +/- 3
P< 0.02
Lactate Dehydrogenase
(LDH)
4864 +/- 588
2411 +/- 512
P= 0.006
Serum albumin
27.4 +/- 0.9
32.7 +/- 1.7
P= 0.017
C-reactive protein (CRP)
56.3 +/- 9.2
80 +/- 25.4
P= 0.305
Neutrophil count
14.9 +/- 1.0
12.2 +/- 1.2
P= 0.238
White blood cell (WBC)
count
19.8 +/- 1.1
14 +/- 1.1
P= 0.021
Anuria (days)
10.4 +/- 2.5
8.1 +/- 1.6
P= 0.692
Length of stay in hospital
(days)
Treatment and initial outcomes of HUS
• Treatment of HUS cases with NSAIDs sig. associated with
renal impairment and death (p< 0.001)
• Treatment of HUS cases with antibiotics sig. associated
with dialysis dependence (p< 0.03)
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71% ‘recovered’
14% had renal impairment
- half of these are dialysis-dependent
8% had neurological impairment
7% deaths
How did the illness affect
patients/relatives?
How did the illness affect patient/relatives?
Recurring Themes (Initial/1 year follow Up)
Emotions
Confusion
Stress
Anxiety
Paranoia
Exclusion
Positivity of care
Reassurance
Blame
Panic
Guilt
Hope
Relief
Depression
Behaviour Changes
Seeking Answers
Physically exhausting Association
between syndrome
V strict toilet regime
and reasons why
Eating habits change developed
Child has OCD
White coat syndrome
Moved to urban area
Wary about hygiene
Inability to absorb
information
Diagnosis of illness
and explanations
Psycho.
Status
Information Given
Psychological Want written info at
trauma
time of HUS – verbal
info not taken in due to
Mentally
trauma
exhausting
Something on hard
Psychological
copy
and
emotional
More info on HUSH
impact on
charity
mother
GPs should have more
Coping levels info
stretched
Conclusions
• VTEC/HUS surveillance less artefactual – enhanced
system
• Farm/rural contact important mode of transmission of
VTEC
• Foodborne E. coli O157 still poses a public health threat
• Ready-to-eat produce unlikely source of infection
• Severity of HUS illness and psychological effects upon
family are devastating
• Vigilance over potential sources for testing - PFGE
Patient presents with diarrhoea
No
Yes
No
Almost certainly not
E coli O157
Is it likely to be infectious?
Yes
Consider sending stool and enquire
about associated cases and biologically
plausible exposures
No
Is it grossly bloody?
Probably not E coli
O157
Yes
Send stool and report to PHPU
Is the patient:
• Under 15 years of age
No
• Over 60 years of age
Unlikely to result in HUS
but observe for 24 hours
• Suffering severe abdominal pain
• Contact of a likely case
Yes
Consult with ID physician/paediatrician
over risk of HUS developing
No
Has the ID physician/paediatrician
advised admission?
Yes
Admit to hospital
Follow consultant
advice