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| March
2, 2001 |
| Cold
Spell Link to Foot-and-Mouth |
By the
BBC's science and technology correspondent Christine McGourty
BBC News
 | | Freezing
weather conditions are not helping the epidemic |
The
cold weather may be contributing to the rapid spread of the foot-and-mouth outbreak,
according to scientists.
They believe the original source may be in meat
illegally imported from a country where the disease is endemic, perhaps in Asia,
South Africa or South America.
The virus is one of the most infectious
found in any animal.
"If the virus infects a cell, within a couple of
hours that cell can be changed from a normal one to something that bursts open,
releasing about 100,000 virus particles," said Professor David Stuart of Oxford
University.
"This means you can get spread from one animal to another
in a herd very rapidly. By the time the disease appears in one cow, it's likely
that the whole herd will have got the disease."
Professor Philip Duffus
of Bristol Veterinary School said the weather conditions were not helping.
'Likes
the cold'
"The problem with this virus actually is it quite likes
the cold, so the weather at the moment is not conducive to its termination.
"What
it doesn't like is being dried and it hates ultraviolet light, so sunlight will
very quickly kill this virus as will heat."
It is thought that in an outbreak
in the Isle of Wight in 1981, the virus was borne on the wind from Brittany, France.
But this time, scientists say it is unlikely to have arrived from any
of England's near neighbours.
A more likely source is in cheap meat illegally
imported from one of the countries affected by the disease.
Professor
Duffus said: "The 1967 outbreak was traced back to a leg of lamb from Argentina
- which was brought in with the virus in its bone marrow, eventually fed to pigs,
and bam!
"That's traditionally how the outbreaks in this country happen
and I would bet that's how this outbreak happened."
He believes that once
the current outbreak is under control, questions will have to be raised about
the globalisation of the meat trade.
Country to country
It was
"crazy", he said, to import meat and meat products from countries where foot-and-mouth
disease is endemic.
Scientists should be able to trace the source of the
virus.
It evolves quite rapidly as it moves from country to country, so
studying its genetic make-up ought to reveal the country of origin.
Though
one problem is that a number of countries do not admit to having the disease and
do not send samples to the experts at Britain's Institute for Animal Health, who
have been studying the viruses involved.
At the institute, scientists
have already discovered the virus is almost identical to one that has been causing
a pandemic disease throughout much of Asia for the last few years.
"For
instance, there was an outbreak of foot-and-mouth disease in Japan last year -
it was the first time they'd had it for 70 years," said Professor Stuart.
"The
virus spread to South Africa and South America so this is a very virulent form
of the virus."
Antibodies
Vaccines do exist against the
disease, but they bring their own problems.
A vaccinated animal produces
antibodies in its blood system that protect it against the disease.
But
an infected animal produces the same antibodies.
So a country testing
imported animals would not easily be able to tell if they had the disease of if
they had simply been vaccinated.
That problem could be overcome, said
Professor Stuart, but it would take time.
It also takes several weeks
for the vaccine to become effective in an animal, he said.
And as the
virus spreads so quickly, the whole of the UK herd would have to be vaccinated
immediately for it to be useful.
Finally, though the virus does not cause
disease in vaccinated animals, it can still produce a persistent infection, which
can sit latent in an animal for up to a year.
'No quick fix'
"If
the animal is subjected to stress, transported around perhaps, then the disease
can come to the surface again and that animal would then be the potential starting
point for another outbreak of the disease," said Professor Stuart.
Professor
Duffus agrees that vaccination is no quick fix.
"Once we start vaccinating,
in my opinion, in terms of animal products we almost become third world.
"No-one
is going to want our products, no-one is going to want our live animals and no-one
is going to want our breeding stock.
"This country still has a great tradition
in producing high quality animals, we can't throw this away." |
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