'Hedges not cull' for cattle TB
08 March 2006 - BBC News
By Richard Black
- Environment correspondent, BBC News
website
Simple
changes in farming practice could stem the spread of tuberculosis in
cattle, new research suggests.
Writing in the UK scientific journal Biology Letters, researchers
say herds on farms with hedges and ungrazed land are less likely to
become infected.
They suspect hedges keep cattle away from badgers, which carry
TB.
A government consultation on TB plans ends this week, and the
researchers say it is "extraordinary" that ministers should be
considering a badger cull.
"It is extraordinary based not only on my work but on the
evidence they collected," said Dr Fiona Mathews, from the Wildlife
Conservation Research Unit at Oxford University.
Their own advisers have put out a report saying a cull could be
counter-productive or have limited effects," she told the BBC News
website, "and still it's being put forward as an option."
The main evidence on culling came from a £35m government-funded
study known as the "Krebs Trial".
It
concluded that culling could be effective if run intensively over
large areas; but a less intensive or scattered operation could
increase disease spread.
Other research has found that cattle movements are the single
biggest factor in TB transmission.
The new study compares 30 randomly selected British farms that
experienced TB outbreaks between 1994 and 1999 against 30 more which
were disease-free.
Scientists used statistical methods to identify issues which
differed between the two groups.
Not surprisingly, outbreaks were more likely where cattle on
nearby farms had already contracted the disease.
But the analysis also threw up several issues of farm management,
with hedges being particularly prominent.
TB was markedly less likely in farms with abundant hedgerows and
ungrazed strips of land along fences; but markedly more likely where
hedges had lots of gaps.
Dr
Mathews calculates that "hedge-poor" farms are 60% more likely than
"hedge-rich" ones to experience an outbreak.
Why hedges and ungrazed strips of land should lower TB incidence
is not clear.
It may be that they keep badgers and cattle apart, preventing
transmission of bacteria; alternatively it could be that either
badgers or cattle living on ecologically managed farms are
healthier, raising their immunity.
However, Professor Christl Donnelly, a member of the government's
Independent Scientific Group on Cattle TB (ISG), cautioned against
reading too much into the results. She said the Oxford team had not
proven a causal link, just a correlation. "The results are interesting, but the key thing is to realise
there aren't any messages about potential disease control options
coming out of this study," the Imperial College London researcher
told the BBC News website.
"Habitat could influence disease transmission; but you wouldn't
want to go out now and tell people to grow longer hedgerows."
Fiona Mathews agrees that more research is needed - and says the
government should pay for it.
"We can't demonstrate that if farmers changed farming practices
they would bring TB down," she said, "but we can demonstrate there
are relationships between farming practice and TB rates, and these
deserve further investigation."
This current study, which was partially funded by Defra, cost a
mere £12,000.
"They
spent millions each year on the Krebs trial," said Dr Mathews. "And
we sat in meeting after meeting with them and asked 'what is the
Plan B if culling doesn't work?'"
She also said Defra blocked access to data gathered since the
Krebs trial began - data which could have led to a firmer
conclusion.
After its consultation period closes on Friday, the government
will develop a strategy to address the spread of bovine TB. It now
costs Britain about £90m a year, a figure which the National
Farmers' Union (NFU) estimates will more than double in the next
five years.
The government has received more than 10,000 submissions.
In December, the government confirmed it was considering a cull
among a number of other options.
But in January, ISG chairman Sir John Bourne cautioned against
culling, say it could lead to an increase in transmission. The RSPCA and other wildlife organisations have been vocal in
their opposition, while the NFU is among groups which support the
idea in principle.
However, it is concerned by reports that the government is
considering giving responsibility to farmers and landowners rather
than managing the cull itself.
A Defra spokesman told the BBC News website: "We will use this
[new research] as part of the science base when making a decision on
whether to introduce a policy which allows the culling of badgers to
control bovine TB in cattle in high incidence areas.
"No decisions have yet been made," he added.
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