|
|
BRIAN
DEER: MATTHEW AND THE BURGER BUG Page 3
By
this time, the investigation of the Morecambe
cluster had enlisted the big guns of science. As
Telford's technicians confirmed each case as an
O157 infection, a sample was posted to the
government's Central Public Health Laboratory in
Colindale, north London, and an e-mail was fired
weekly to the Communicable Disease Surveillance
Centre, which is based at the same site. The
central laboratory, which was founded in 1946,
has an annual budget of £10m and employs some
400 staff. It is the nerve centre for tackling
infectious diseases, such as Aids, tuberculosis
and meningitis.
The
lab's scientists have published cutting-edge
research on E-colis of every description. The
core of these bacteria are minute tube-like
cells, which have been classified through
proteins in their skin (so-called "O"
antigens) into 173 different sorts. Radiating
from these cells are little tails, or flagella,
which in turn are classified by another antigen
("H"), of which 55 have so far been
found. Going a stage further, the O157:H7
organism, involved in the recent British
outbreaks, has been sorted into around 80
different types, and the most modern technologies
can go even deeper and fingerprint its DNA into
thousands of individual strains.
Compared
with other infectious agents, O157:H7 is not that
common, but it is causing anxiety among
scientists because it is incomparably nastier
than most. It is astonishingly resilient: able to
live in the kind of conditions that would kill
other bugs. On farmland, it can survive in the
soil for up to six months, while in kitchens it
can cling to cool, dry surfaces and shrug off
many household cleaners. Unlike infections such
as salmonella and campylobacter, which require
millions of bacteria to cause human sickness, as
few as a dozen of the new E-coli are needed. And
when it strikes old people, or children of
Matthew's age, it can leave them in a critical
state.
Rachael's
sons' samples, along with the other children's,
were sent to Colindale for what is called
"phage typing", which can give clues
for investigating outbreaks. Using a
handle-cranked contraption on a second-floor
laboratory bench, technicians stamp dishes of
E-coli with 16 viruses which attack bacteria. By
later reading which viruses attacked what, the
organism in the dish is given a rough-and-ready
type. In the Lanarkshire outbreak, for example,
where cross-contaminated ham had been sold by the
local butcher, Scotland's equivalent lab, at
Aberdeen, identified each patient's specimen as
containing a type 2 E-coli bug.
But
Colindale's typing of the Morecambe cluster
produced a startling result. Matthew's and Tom's
specimens, along with the 11-year-old boy's, came
up as type 2. The six-year old girl's, however,
was typed 8. The girl aged 14 months who had been
abroad was apparently infected by type 34. And
there was a 21 and a 32 as well. Since an
outbreak should involve bugs of the same type, it
seemed that, whatever the source of Rachael's
sons' infection, it was not the same as all of
the others, despite the links of place, time and
age. It looked as if the cluster was only a
bizarre coincidence.
The
environmental health officers took this as good
news: there was no Lanarkshire-style outbreak on
their patch. Brownjohn and Mann felt that nothing
further would be gained by carrying out any more
inquiries. No food or other samples were taken
from Rachael's home. The nearby allotment, where
the children picked apples, was not investigated
for infected manure. And, although both she and
her boys regularly mixed with other children and
parents, no contact-tracing was done to check the
possibility of person-to-person spread. Even in
the face of Matthew's deteriorating condition,
the investigation was brought to an close.
But,
far from being grounds for confidence, the hidden
story of the Morecambe cluster may have been more
disturbing than even the Scottish crisis. It is
hardly credible that an infection judged to be so
rare that doctors, laboratory staff and
environmental health officers give it scant
attention should strike eight children in one
place and at the same time without any
explanation. It is possible that either the phage
typing was wrong - and insiders say it often is -
or, if they were infected with different types,
then that suggests there is more E-coli around
than has so far been acknowledged. In short, that
Morecambe was the tip of some iceberg of hidden,
unreported, infections.
The
clue that there may have been more to know is
found in statistics compiled at Colindale by the
Communicable Disease Surveillance Centre. During
the week that Matthew became ill, these showed a
dramatic and unexplained leap in O157 reports. In
the week before the first day of his illness
there were 24 notifications in England and Wales
- more or less last year's weekly average. In the
week beginning the Monday after, Day 8, during
which he was admitted to hospital as an
emergency, there were more: 52 reports. But
during the seven days between - the week ending
September 19 1997 - the numbers pouring in from
labs such as Telford's totalled a staggering 103.
What
this spike in the graph points to may have been a
national outbreak which was not so connected by
geographic location to come to local authorities'
attention. With foodstuffs often transported
hundreds of miles from central processors and
packagers, Rachael's boys may have been connected
to many others by exactly the kind of
"low-level contamination" which the
Morecambe investigators had suspected. "We
felt we were seeing a local aspect to a national
problem," says a member of the local team.
"Intuitively, we felt that was the best
bet."
A
review of the evidence stacked up so far supports
this intuition. Most infections in healthy adults
produce no or only minor symptoms. Most hospital
labs do not routinely test for E-coli, so its
true incidence is unknown. No statistics are
compiled on e coli-related disease. And the
number of deaths cannot be calculated because
certificates rarely cite the infection. With the
bug's resilience and ability to trigger illness
in extreme low doses, it could easily have got
into a mass-market product last year, been
distributed throughout the UK during September
and caused apparently unconnected sickness in
children from Land's End to John O'Groats.
If
Matthew was the victim of such events, the
central laboratory could expose the fact. But
again the child was let down by a system that
undervalues the E-coli threat. Although
Colindale's phage typing sounds impressive and is
carried out on all samples received at public
health laboratory's labs, it is a cheap, quick,
crude and virtually clapped-out technology,
devised half a century ago to classify
salmonella. More than one third of all O157
strains are lumped together in this system as
type 2 - far too big a group to track through the
food chain. And although the more sophisticated
DNA fingerprinting technique is available at
Colindale, it is not routinely used, on grounds
of cost.
Once
more it was question of the priority for E-coli -
and whether the specialists and authorities that
are charged with fighting it are doing everything
that the public would expect. "Everybody has
limited funds," says Tom Cheasty, a senior
researcher at the central laboratory. "The
way we are financed and staffed, we couldn't do
all the work that would be needed to be done on
everything. We wouldn't have enough hours in the
day. If people spent more time looking at this
bug they would have to spend less time looking at
some of the others."
But
the new fingerprinting technique (called
"pulsed-field gel electrophoresis")
could have analysed the DNA in Matthew's and
Tom's samples and not only matched the precise
strain of the organism present against the other
Morecambe children's, but also against those
involved in all of the other infections reported
to north London that week. Each family affected
could have been interviewed as Rachael was and
common sources readily identified, wherever in
Britain they might be.
To
fingerprint all of that week's 103 samples might
take a technician three months and cost £6000,
but such DNA testing combined with new methods of
detecting the organism in foodstuffs and bar-code
tracing of products through the food chain, could
transform the response to E-coli. Not only could
rogue producers or packagers be nailed, but also
bad practices at abattoirs, dangerous activities
such as spraying animal remains and cattle faeces
on farmland, and the continued sale of high-risk
milk, could all be swiftly tackled. Some
scientists believe there would be the long-term
chance of eliminating the bug altogether.
Although
Colindale cites the pressure of other work, the
main beneficiaries of not using the new
technologies may not be other research
priorities, but the giant food and farming
enterprises whose lapses may remain undetected.
If tests linked disparate cases of illness such
as the Morecambe victims' with batches of common
products, such as, say, ham or milk, public
opinion could force severe government action, as
it did over BSE. And after the wholesale
slaughter of cattle brought about by inquiries
into two dozen human deaths from new variant CJD,
business could be forced into another round of
costly remedies to clean up its act.
But
if the winner is business, the loser is the
consumer - leaving parents such as Rachael to
think that illness must be due to something in
the home. On the day that Brownjohn called and
interviewed her, the things that stuck in her
mind most strongly were questions about her
habits. Which shelf in the refrigerator do you
put cooked meats on? Do you always clean knives
after cutting? Could you show me, please, how you
wash your hands? Let me look at the kitchen
again.
Brownjohn
left her thinking that she was to blame for the
state of her little boy's health.
*****
This
report is copyright, Brian Deer. Responses,
information and other feedback concerning this
resource on e-coli o157 food poisoning are
appreciated - via the briandeer.com homepage.
|
|
