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pressure and often inaccurate reporting, has been intense at some periods.
Rather curiously, the first report of spongiform encephalopathy in a cat-not a
species that is eaten-apparently had a greater effect on beef consumption m
Great Britain than the epidemic m cattle, presumably reflecting a fear that tf
one species barrier could be breached, so could others. A policy of scientific
openness, combined with independent advice from the Spongrform Encepha-
Handling the BSE Epidemic in the UK 189
lopathy Advisory Committee (SEAC), has helped to provide a more balanced
assessment of the situation and of the measures taken to protect human and
animal health. In the long term this has probably been more effective than
publicity stunts, however well intentioned.
5. The Role of Research
It has been made clear already that BSE was recognized quickly because an
effective surveillance system for new and emerging diseases existed m Great
Britam. The transmissible spongiform encephalopathies (TSEs), especially
scrapie, had been studied in great detail already, and an immediate response
was possible because of the general laboratory and epidemrological resources
of the MAFF and the specialized research staff and facilities at the Neuro-
pathogenesis Unit (NPU) of the Agriculture and Food Research Council
(AFRC). The scientists recognized the pivotal importance of transmission
experiments, which were set up before formal funding had been arranged.
The Southwood Committee perceived the importance of research and rec-
ommended that a large observational study be set up to establish whether BSE
was maternally transmitted from dam to offspring. This was done, and results
are expected m 1997. They also recommended that a further committee be set
up to review the need for research. Thus, the first “Tyrrell” committee, com-
posed of a small but diverse group of scientists with interests m the area, was
constituted in February 1989. It reviewed the questions that needed answering
and suggested experimental or other approaches, and graded the priority of
each proposal. The committee reported in June 1989, but their report was not
published until the followmg year, when sources for the required funding had
been identified. By the trme the report was published all high and medium
priority research that it identified had been started. Funds were made available
to support MAFFiNPU research and also to support a new research mitiative
by AFRC, which was open to universities and research institutes, to study
basic aspectsof TSEs. This committee was then converted mto the Spongiform
Encephalopathy Advisory Committee (SEAC), still under the chairmanship of
Dr. Tyrrell, which met every 4 mo, and more often if necessary, to review the
development of the epidemic and the results of research as they became avail-
able, and to answer questions posed by the Department of Health and the Min-
istry of Agriculture.
The government™s intention was to base its response to the epidemic on
independent scientific advice, and to be open about what was being done and
why. Previously it had been said that the work of Mmrstry scientists was not
published sufficiently freely and it was intended that there should be no delay
m implementing changes recommended as a result of any new findings. These
intentions were not always easy to put into practice. The Minister might say in
190 Tyrrell and Taylor

Parliament, “What the Tyrrell Commtttee recommends, I will do,” but despite
their sctenttfic expertise the Committee members often knew little of the detail
of farming practices or of the relevant laws and regulattons and could only
express general views and sctenttfic prmciples that had to be interpreted and
Implemented by others with appropriate expertise. Nor could the commrttee
assess how scrupulously the regulations were observed and enforced As to
openness and pubhcatton, tt was somettmes decided to report experiments that
were only partly completed, m spite of the risk that the conclustons drawn and
consequent actton taken would have to be modified when all the results came
in. Work therefore was sometimes published sooner than would have been the
case tf purely scientific edttortal crtterta had been used Although there may be
benefits m avotdmg delay, such a pohcy also carries the risk of overreactton to
an isolated finding seen out of context. The Committee generally tended to
take a “fall safe” view of experiments that had possible public safety tmphca-
tions For Instance, when unexpectedly parenteral mjectton of BSE caused
mfectton and clmtcal disease m pigs, they advtsed that the ban that already
prevented the use of specified bovine offal m human food should be extended
to prevent feeding to pigs and poultry and all other animals and birds as well,
even though there had been no evidence that a TSE had ever occurred naturally
m either pigs or poultry, despite the fact that both had consumed large quanti-
ties of rummant protein in feed. On the other hand when, earlier than expected,
mfecttvity was found m the distal ileum of calves that had been given a mas-
stve dose of BSE by mouth, then advtce was that the epidemic was declining in
response to the control measures already m place, so that any risk that ttssues
from calves under 6 mo old would expose humans to risk was “minuscule or
absent ” Despite this advice the government decided to be ultracauttous and
amend the regulations to prevent the use of intestines and thymus from cattle
of any age, rather than only applymg the ban to these tissues from cattle 6 mo
of age and older

6. Medicinal Products
The Medicines Control Agency, through the Committee on the Safety of
Medicines, also had a role m protecting the public health. If BSE was a hazard
to humans then the greatest risk would be from products given or used parenter-
ally, such as vaccmes, suture materials, and so on. This was a potentially seri-
ous problem since healthy animals might be infected, and by analogy wtth
scrapie there was no stertllzatton method that was likely to eliminate mfecttv-
tty without destroymg the product. In addmon, any risk from parenteral use
would be expected to be greater than from oral consumption. The Agency there-
fore Issued guidelines and sought mformation from all manufacturers to find
out tf bovine materials were used m then products. One attractive solution was
Handling the BSE Epldemlc In the UK 191

to source bovine materials from irreproachably BSE-free herds: The Ideal
would be from well-supervised herds in a country where neither scraple nor
BSE were present. It is impressive that industry took up thts challenge very
effectively; for instance, intestines for the manufacture of surgical catgut were
sourced from Australasia within months.
7. Spongiform Encephalopathies in Other Species
It gradually became clear that the host range of BSE was wider than that of
scraple. Exotic ungulates m zoos had been fed the same rummant-derived pro-
tem as cattle and several speciesdeveloped SEs. In due course, laboratory stud-
ies showed that the agent causing disease m these species behaved like BSE
when maculated mto a panel of genotyplcally susceptible experimental mice.
In addttion, domestic cats and great cats in zoos developed SEs and strain typ-
ing, again suggested that the agent responsible was similar to BSE. Members
of the Pet Food Manufacturers Association voluntarily had decided to exclude
specified bovine offals from then- products when the possiblhty of banning
these tissues for human consumption was first discussed m 1989, but the ban
nevertheless was extended to cover all animal species m September 1990 after
the experimental transmission of BSE to pigs by simultaneous intracerebral,
intravenous, and intraperltoneal moculatlon. There are no data to indicate the
number of other species that received the same potentially contammated feeds
as cattle, or were fed specified bovine offals before the bans were imposed, but
nevertheless did not develop a spongiform encephalopathy. It is probably far
greater than the number m which disease has been observed. No specific moni-
toring of unaffected species has been planned but if sponglform encephalopathy
is suspected as a result of laboratory examination of brain tissue from any am-
ma1species, the fact must be notified so that further official mvestlgatlons can
be undertaken.
8. CJD Epidemiology
The Spongiform Encephalopathy Advisory Committee considers that all the
measures necessary to protect public health are now m place, and that beef
produced m the United Kingdom 1ssafe to eat. The Southwood working party
considered the possibility that BSE would affect humans to be “remote,” even
if no preventative measures were taken. However, the posslblhty of human
susceptibility could not be ruled out entirely, and control measures were rec-
ommended and implemented. Heeding the historical injunction to “think it
possible that ye may be mistaken” the working party also recommended that an
earlier survey of the occurrence of CJD in England and Wales should be reac-
tivated nationally. This was done by providing a small unit m Edinburgh wrth
resources and expertise to ascertain and investigate all clmically possible cases
192 Tyrrell and Taylor

and carry out the necessary postmortem and epidemrological studies. The CJD
Surveillance Unit produces annual reports and has had to cope with the prob-
lems of publishing information about prelimmary, and thus unreliable, lind-
mgs, such as when the incidence of CJD appeared to rise the year after they
started work, and when dietary enquiries m 1992 suggested a hnk between
eating “puddmgs” (a kmd of sausage) and developing BSE Neither findmg
was repeated in the 1993 study; the number of CJD cases fell and the spurious
association with “pudding” consumption disappeared, only to be replaced by
other, equally improbable, supposed risks. The problem of recall bias makes
such studies particularly drfficult to interpret

9. Relations with the Media
It was not difficult to predict that there would be public concern about a
previously unknown and mvariably fatal disease of cattle, transmitted by con-
taminated feed and that resembled a number of known fatal diseases of humans.
Furthermore, the public was surprised to be told that there was no test that
could identify infected live animals, and that the epidemic would have to be
mvestigated, at least at first, by methods of clmical observation, histopathology,
and “shoe leather” epidemiology that had been used for 100 yr or more. The
new epidemic also took place against a background of MAFF and DoH
mvolvement m controversy over drseases such as salmonellosis and hsteriosls,
which originated from contaminated food.
The catchy, but inaccurate, name “mad cow disease” was coined and the sad
spectacle of a sick ataxic cow sinking to the ground, taken from the video
produced to educate farmers and veterinary surgeons about the new disease,
was screened and rescreened. It might, m retrospect, have been better to name
the new disease “Cattle Scrapie”-as the French did subsequently-than to
corn the scientifically correct but hard to say “bovine spongiform encepha-
lopathy.” Cases of CJD in two dairy farmers were claimed to be evidence that
BSE had been transmitted to humans, and much publicity was given to a young
woman reduced to a chronic vegetative state with a condttron that resembled
(but since she was still alive could not be confirmed as) CJD, who had eaten
hamburgers earlier in her life. Even the lack of any definitive diagnosis m the
latter case did not deter critics from claiming that the case was further “proof™
that BSE had been transmuted to humans, even though the detailed studies
made this very unlikely
In these and other ways pubhc concern was fuelled by intelligent mdtvidu-
als who questtoned the assumptions, and later the basic science, on which con-
trol measures (particularly those that protected public health) were based
Rather than using the well developed scientific fora to debate these issues, they
made It their business to express their doubts to the populatron m general
Handling the BSE Epidemic in the UK 193

through the newspapers, television, and other areas of the media, often m
apocalyptic terms and with a highly selective presentation of information. Such
confrontational tactics made excellent publicity, but did considerable dtsser-
vice to attempts to implement a rational control policy firmly based on scien-
tific evidence.
10. Effects on Farming
No epidemic involvmg the death or compulsory slaughter of more than
166,000 adult cattle over a period of more than 7 yr can fail to have an effect on
the farming industry, but this has probably not been as great as might have
been expected, and many of the problems have been caused by the mterna-
ttonal response to the UK epidemic rather than domestic circumstances.
E:ven at the peak of the epidemic, in 1992 and early 1993, only one m every
100 adult cattle were slaughtered as suspects,and two-thtrds of breeding herds
have never experienced a case of BSE. Of the herds that have had cases, 37%
have had only one, and 72% have had four or fewer. In terms of normal cullmg
and replacement these figures are msignificant, although the onset of disease
does deprive the farmer of the ability to choose which animal to cull. Compen-
sation has been generous, and except m the case of pedigree cattle there has
been little or no financial loss when a suspectanimal has been slaughtered The
costs of diagnosis and disposal also have been borne by the government, and
some &157 million (approx $240 million) has been paid already m compensa-
tion and disposal costs.
Perhaps the greatest domestic effect has been the temporary drop in beef
consumption that occurred m 1990, following the discovery of spongiform
encephalopathy m a domestic cat. Beef consumptton fell by 30%, but subse-
quently recovered over a period of about 1 yr. A handful of education authori-
ties continue to ignore scientific advice and prohibit the use of British beef m
school meals, but the great maJority either took no action m 1990, or have
rescinded the decisions they took then. UK agriculture also has been adversely
affected by the actions of other countries throughout the world m response to
the BSE epidemic.
11. International Repercussions
Relatively few countries have reported cases of BSE, and the disease has
occurred at high incidence only in the United Kingdom. Nevertheless, there
has been considerable interest in the disease, and the response to isolated cases
has often been guided by political rather than sctenttfic considerations. The
situation has not been helped by the response in some countries when a single
case of BSE has been reported m an imported animal m a country that is other-
wise free of the disease. Some countries have slaughtered the entire herd In
194 Tyrrell and Taylor
which a case occurred, and others have attempted to identify and destroy all
cattle tmported from the United Kingdom, even though most were beef cattle
and some more than IO-yr-old. Neither response IS scIentifically justified.
Both the World Health Orgamzation (WHO) and the Office International
des Eptzooties (OIE) have considered BSE and issued appropriate advice. The
latter organization has adopted a chapter m the International Animal Health
Code, together with a supportmg scientific document, which advises member
countries of the measures necessaryto allow safe trade m cattle and cattle prod-
ucts from countries where BSE occurs, or may occur, at high or low mctdence.
Although adopted unanimously the recommendations have been ignored, m
whole or in part, by most member countries, and m some cases restrictions
have been placed on the importation even of products that OIE recommends
can be imported unconditionally without risk
A number of countries have assessedthe risk of BSE occurring as an mdrge-
nous disease, but none so far has identified the same combination of factors as
existed in the United Kingdom in the early 1980s. The risk of a maJor mdtg-
enous epidemic arising m any country therefore 1sconsidered to be low, and
the application of preventative measures based on British experience could
remove any risk there is. However, sometimes tt is more dtfficult to do what 1s
necessary than to know what 1snecessary, and there may be considerable resis-
tance to the mtroduction of preventative measures against a disease that has
never been recorded in a country.
12. Continued Monitoring
The BSE epidemic m Great Britain probably has been studied and mom-
tored more intensively than any other cattle epidemic in history, and the mfor-
mation obtained from the eptdemiological study has been vital to the control of
the epidemic and m monitormg the effectiveness of control measures The long
mcubatton of the disease made a quick response to control measures impos-
sible, and until 1991 the number of casesapproximately doubled from one year
to the next. The effect of the feed ban was to remove, or at worst substantially
reduce, the risk of infection for cattle born after July 1988, but initially this
effect was more than offset by the increasing amount of mfectivity present m
feed, as a result of recycling, until July 1988. Despite official confidence in the
effectiveness of the measures that had been taken, it was a considerable relief
to observe the age distribution of casesbeginning to change, and the number of
suspect casesbeing reported (and placed under restriction) reaching a peak and
then declining (see Fig. 2).
The accelerating decline m the epidemic does not, however, obviate the need
for continued careful momtormg. Although much has been discovered, and the
effectiveness of the measures taken to control the epidemic been demonstrated,
f
196
there ts still much to be learned Continued momtormg 1s necessary to see
whether there is any change in the pattern of the disease or how it is transmn-
ted, and to check that new strains of the agent, perhaps with different charac-
tenstics, do not evolve. The continued flow of mformatton obtained from
monitoring, and from research, will enable the control program to be adjusted
expedrtiously if necessary, and its publicatron wrll provide the mformatron
necessary for any other country to prevent an outbreak occurrmg, and to con-
trol an outbreak that does.
13. Conclusion
The UK response to BSE has provided a model of how to deal effecttvely
wtth a previously unknown disease, basmg the lmmedtate response on sound
scientific prmcrples and arrangmg and funding the research needed to build on

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