Attachment 7
THE MOST IMPORTANT GASTROINTESTINAL INFECTION
VERO CYTOTOXIN-PRODUCING ESCHERICHIA COLI O157 (VTEC O157)
PUBLIC HEALTH
IMPORTANCE
Since it was first discovered to be a pathogen
in the late 1970s, Vero cytotoxin-producing Escherichia coli
(VTEC) have made their presence felt world-wide. Large outbreaks
in the United States of America, central Scotland, Japan and,
most recently, in Canada highlight the morbidity and mortality
associated with this organism. In the United Kingdom the predominant
pathogen is VTEC O157 and over 1,400 cases were confirmed by the
PHLS Laboratory of Enteric Pathogens (LEP) and the Scottish E.coli
O157 Reference Laboratory in 1999. The principle reservoir of
infection is in cattle and the majority of human cases (>80
per cent) are sporadic (ie are not associated with outbreaks).
The public health importance of VTEC O157 is
manifested by:
— The substantial morbidity and
mortality associated with infection. Severe complications
of VTEC O157 infection include haemolytic uraemic syndrome (HUS),
which mainly affects children, and thrombotic thrombocytopoenic
purpura (TTP), particularly in adults. Both these complications
carry significant mortality. For children developing HUS who survive
a substantial proportion suffer long term kidney and/or brain
damage.
— The fact that infection is not
treatable. Therapeutic options are very limited. The mainstay
of therapy includes correcting and maintaining fluid and electrolyte
balance and monitoring patients for the development of HUS. A
recent cohort study from the United States lends further evidence
that antibiotic treatment might do more harm than good.
— The range of modes of transmission
and low infectious dose. Although VTEC O157 infection was
first recognised as food-borne, evidence accumulated from outbreak
investigations and from studies of sporadic cases demonstrates
several modes of transmission from the animal reservoir (food,
water, environment and animal to person). Person-to-person transmission
has also been demonstrated in outbreaks in households, nurseries,
hospitals and nursing homes. Spread of infection by any of these
means is facilitated by the fact that the infectious dose is,
apparently, so small.
— The enormous cost in social and
economic terms. The economic consequences of VTEC O157 are
considerable with the cost of a single (large) outbreak having
been estimated at £11.9 million over 30 years.
DANGERS OF
NOT ACTING
Transmission to humans will continue to occur
via contaminated food, water, environment and animals. The current
waterborne outbreak of VTEC O157 infection in Canada 2,000 cases
is a salutary reminder of the consequences of inaction.
ORGANISATIONAL ARRANGEMENTS
A variety of professionals/agencies is involved
in tackling VTEC O157:
— at the level of individual patient
care; GPs, hospital staff, health and local authority staff, the
Public Health Laboratory Service;
— at population level; health and local
authorities, the Public Health Laboratory Service, the Veterinary
Laboratories Agency; and
— at national policy level; the Public
Health Laboratory Service, the Veterinary Laboratories Agency,
the Food Standards Agency, the Department of Environment, Transport
and the Regions (Drinking Water Inspectorate), the Ministry of
Agriculture, Fisheries and Food, the Department of Health, the
Health and Safety Executive and the various territorial departments
in Scotland, Wales and Northern Ireland.
CURRENT ORGANISATIONAL
ISSUES
At national policy level the responsibility
for VTEC O157 is split across government departments according
to mode of transmission. The PHLS is the only organisation which
has a complete overview of the public health implications of VTEC
O157 in England, Wales and Northern Ireland. In Scotland the same
applies to the Scottish Centre for Infection and Environmental
Health (SCIEH). Collaboration between the PHLS and SCIEH is very
strong. However, the government departments involved north and
south of the Scottish border might respond differently as has
been witnessed this week by the formation, in Scotland, of a Task
Force to combat VTEC O157. It is understood that there are no
such plans for England, Wales or Northern Ireland.
POTENTIAL SOLUTIONS
Primary prevention of VTEC O157 is, at the moment,
the only option for reducing the human toll of morbidity and mortality.
This requires a wide range of activities targeted at several modes
of transmission. There is an opportunity to develop a UK solution
to what is undoubtedly a UK problem. The Task Force concept, involving
all the key players, should be taken forward on a UK basis.
CONCLUSION
Given the seriousness of human VTEC O157 infection,
the lack of therapeutic options and the apparent lack of control
measures for the animal reservoir, blocking transmission pathways
is essential for reducing the morbidity and mortality from this
serious disease. This requires a genuinely collaborative response
right across the spectrum and including industry (farming, food,
catering, water etc.) "Joined up" government needs to
be just that.
Prepared by Drs Sarah O'Brien, Goutam Adak,
Robert Mitchell, Henry Smith, Frederick Bolton. Public Health
Laboratory Service.
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