MANY parts of Britain are closed to visitors. The tourist industry is losing
millions every week. The general election may be postponed. And over a million
perfectly healthy cattle, sheep and pigs are being slaughtered in a desperate
bid to end the epidemic of foot and mouth disease.
As the carcasses pile up, some experts are questioning the no-vaccination
policy of most developed countries. The relentless rise in international trade
and tourism means preventing such outbreaks is getting harder and harder, while
new vaccines and tests mean there鈥檚 no reason why countries that vaccinate
shouldn鈥檛 export, they say. The policy may now be more an excuse to bar cheap
meat imports than it is sound science.
The Netherlands already plans to use emergency vaccination if its outbreak
gets out of control. This means inoculating all animals within 3 kilometres of
an outbreak and then slaughtering them later. There are hints that Britain might
follow suit.
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But Belgium and the Netherlands want to go much further. They are asking the
European Union to let them use vaccines routinely. Most EU countries say no. The
big problem with vaccination is that some vaccinated animals only become weakly
immune. This means they can still be infected and possibly pass the disease to
other animals yet not show any obvious symptoms. This is why disease-free
countries won鈥檛 buy animals, meat, embryos or semen from countries that
vaccinate.
Stopping vaccination, in contrast, makes it easy to tell if animals are
disease-free, as any stray pathogen will trigger full-blown disease. 鈥淚f you
don鈥檛 stop vaccinating, you never know if your animals are infected,鈥� says Jim
Pearson, head of the scientific department at the OIE, the world organisation
for animal health in Paris.
Gareth Davies, former chief epidemiologist at Britain鈥檚 ministry of
agriculture, was one of the architects of the EU decision to abandon FMD
vaccination in 1991. At the time, the vaccines were part of the problem.
Standard vaccines are made from killed virus. But not all the viruses were being
destroyed, so vaccines were actually causing most of Europe鈥檚 outbreaks, while
infection came from elsewhere only occasionally. The same was true for classical
swine fever. 鈥淥n the whole,鈥� says Davies, 鈥渢he benefits of non-vaccination
outweighed the costs.鈥�
Global travel may be moving the goalposts, though. 鈥淣ow anyone can fly in
from anywhere carrying infected material,鈥� says Davies. The EU is the biggest
single destination for international travellers, with arrivals growing by 4 per
cent a year. Travel to the US grew by 19 per cent between 1998 and 2000. And all
it takes to start an epidemic is a carelessly discarded sandwich containing meat
from an infected animal.
Accidental introduction isn鈥檛 the only threat. Brazil blames sabotage for an
FMD outbreak last year. And the US is so worried about bioterrorist attacks on
its livestock industry it has just spent $40 million on upgrading its
secure research facilities for animal disease on Plum Island, New York.
Davies now thinks vaccination is worth considering again鈥攂ut only as an
emergency measure. The Netherlands plans to do this because it believes
vaccination would have eased the nightmare of its 1998 swine fever outbreak.
However, the country will only regain FMD-free status several months after it
slaughters vaccinated animals.
Then it can sell meat to FMD-free North America and Japan again. Meat from
vaccinated animals is unacceptable there because of the risk of sub-clinical
infection鈥攂ecause officially, you can鈥檛 tell vaccinated and infected
animals apart.
Except you can. The current FMD vaccine consists of dead viruses. Animals
given this vaccine make antibodies to the virus鈥檚 protein coat, but will never
be exposed to the other viral proteins made when the virus infects a cell. In
1999, the European Commission鈥檚 scientific committee on animal health concluded
that tests for non-coat proteins would distinguish vaccinated from infected
animals 90 per cent of the time.
Other researchers have even developed specific 鈥渕arker vaccines鈥� designed to
make this task easier. For example, Rob Moormann of the Dutch Institute for
Animal Science and Health in Lelystad has created a marker vaccine for classical
swine fever.
An accuracy of 90 per cent cannot guarantee that each animal tested is clear.
But the European Commission has said that it is good enough to declare a herd
uninfected鈥攊f 90 per cent of animals are clear, then the rest probably
don鈥檛 have the disease. Despite this, the Commission decided against using
either vaccine.
This makes Moormann angry. 鈥淟ook at the cost of these recent outbreaks. It
would be better to do routine prophylactic vaccination, then good surveillance
for infection.鈥� He says slaughterhouses could routinely test for these
infections along with BSE. Such tests should soon get a lot quicker and cheaper.
The US military is already developing 鈥渂iochips鈥� to detect biological weapons,
for example.
Routine testing for 20 diseases on one chip could bridge the gap in
veterinary surveillance that let Britain鈥檚 FMD outbreak spread for weeks before
it was spotted. More to the point, says Moormann, farmers could vaccinate their
livestock and still pick up any stray infection. 鈥淚t would cost a lot less to
speed the development of this technology than to pay for more big
辞耻迟产谤别补办蝉.鈥�
The EU Court of Auditors agrees. In a scathing review last year of swine
fever management, it wrote: 鈥淭he Community鈥檚 non-vaccination policy . . . is
called into question by the development of marker vaccines, and the very high
costs associated with the 1997-8 epidemic. The Commission should update its
cost-benefit analysis.鈥�
Mirjam Nielen, an animal health economist at Wageningen University in the
Netherlands, is doubtful, though. 鈥淵ou would have to pay a lot for surveillance,
and you would have to convince your trade partners you really are disease-free,鈥�
she says. Convincing disease-free countries such as the US to accept imports
from countries that vaccinate livestock won鈥檛 be easy.
And there is also one big, unspoken benefit of not vaccinating. Under its
current policy, says Nielen, 鈥渢he EU can keep out imports from a lot of
countries. That probably keeps out lots of odd diseases鈥�. It also means EU
producers face less competition.
Over 78 per cent of the EU鈥檚 meat is sold internally. If the EU started
vaccinating against diseases such as swine fever and FMD, it could no longer
refuse to import meat from Russia, much of Africa and South America. That might
explain why the EU is at such pains to hang on to its disease-free status
although the main benefit, at least officially, is that the EU can export meat
products to North America and Japan. Yet even in 1999, before beef exports were
banned, only 5 per cent of the EU鈥檚 sales were to these countries.
鈥淐ountries will only go back to vaccinating if the costs of not vaccinating
look really enormous,鈥� says Nielen. Many farmers and businesses in Britain think
the costs are already too high.
