Bovine TB Risk in Britain:
Past and Present
Badgers may not be the sole cause of TB in cattle
What led to the spread of tuberculosis in cattle and badgers in Britain? This podcast narrated by Paul Ging includes a highly informative interview with Professor Peter Atkins who led two recent studies on the subject with PhD student Philip Robinson from the Department of Geography at Durham University.
While the controversial badger cull to be implemented once again this summer by government
has led to a polarised debate between securing the welfare of the country’s
badgers and protecting farmers’ cattle, research led by Atkins provides
historical insights that could help better inform policy in preventing the
spread of TB.
An interesting point to note is that the Randomised Badger Culling Trial, which
is often referred to as evidence that culling badgers will control bovine
tuberculosis, came to the following overall conclusion, which appears
inconsistent with assertions made by government today:
10.92 Our overall conclusion is that after careful consideration of all the RBCT
and other |
REFERENCES:
‘Bovine tuberculosis and badgers in Britain: relevance of the past’.
Epidemiology and Infection. doi:10.1017/S095026881200297X
‘Coalition culls and zoonotic ontologies’. Environment and Planning A.
See the transcript of the podcast below:
(Narration)
Paul Ging:
Tuberculosis in animals and in humans has a long history in the UK.
Recently it’s been especially troubling for farmers and their cattle in the West
and Southwest of England. Tuberculosis or TB is an airborne infectious disease
caused by a bacterium that attacks the lungs and other parts of the body. It’s
widely known to be carried by certain species of animals known as wildlife
reservoirs, of which the European Badger is one.
More recently the risk of cattle contracting TB has gained widespread attention
as large numbers of cattle infected with the disease have been reported.
According to Defra, the UK Department for Environment, Food and Rural Affairs,
twenty-six thousand cattle were slaughtered in 2011. TB control in England cost
taxpayers 500 million pounds in the last 10 years.
Some farmers and scientists point their fingers at the badger as the cause of
the recent outbreak, but the view that the badger is responsible for the recent
spread of TB in cattle has been highly controversial amongst researchers and
also with the public. Policy to enact a badger cull in attempt to control the
spread of TB was passed by government last year, but the cull has been held off
until this summer.
The plan to cull England’s badgers has been met with outrage from interest
groups such as the Badger Trust and animals rights activists throughout the
country. The National Farmers Union and scientists with Defra say culling the
badgers would reduce the spread of TB in cattle. But are badgers really solely
to blame for the recent spread of bovine tuberculosis?
Professor Peter Atkins is from the Department of Geography and Institute of
Hazard, Risk and Resilience at Durham University. He has investigated the spread
of TB in cattle in England in new research, and he doesn’t think it’s quite that
simple. TB has a long history in the UK, especially in cattle where the disease
has spread quite quickly throughout the country over the past decades and has
shown resilience to several government attempts at eradicating it.
(Interview)
Prof Peter Atkins:
Bovine tuberculosis has been around for almost several
hundred years, we certainly have evidence of this in the early 19th century,
both in Britain and in other continental countries, but it seems to have been
concentrated especially in Britain because of the intensive cattle breeding and
capital-intensive agriculture in this country from the 18th century onwards.
So if you had one animal that was infected it was quite likely that the other
animals would become infected as well. And what tended to happen was is that the
disease spread through the air, so if you keep your cattle confined in a cattle
shed without in terms of too much in terms of ventilation then the disease
spreads. So we think the peak of bovine tuberculosis probably was in the middle
or late 19th century.
(Narration)
Paul Ging:
Prior to 1960, bovine tuberculosis was concentrated in the counties
with the most intensive dairy farming especially in the Northwest, but also the
West Midlands, the Southwest and parts of Wales and Scotland. In order for
farmers to test their cattle for bovine tuberculosis they used what is called
the ‘tuberculin skin test’ where a small amount of the TB bacterium is injected
into the animals’ skin, causing an allergic reaction if they are infected. The
test revealed that a large proportion of England’s cattle were infected with TB.
(Interview)
Prof Peter Atkins:
The skin test in the early 20th century showed the figure was
sometime like 40 or 50 percent but almost certainly it was higher than that
because firm farmers in Cheshire weren’t putting their cattle forward to be
tested if they knew that they were diseased. So we think the figure might have
been 60, 70 even 80 percent of cattle. Which is a very high figure indeed.
After the Second World War the British government attempted to eliminate bovine
tuberculosis by slaughtering all cattle in the country that tested positive for
the disease. Any cattle showing the smallest sign of TB were killed leading to
the slaughter of entire herds of cattle. The rate of TB dropped dramatically in
the 1950s and by 1960 the country’s cattle herds were TB free.
And it seems very likely there would have been other animals having the disease
as well. So I’m thinking of the wildlife reservoir which includes badgers and
some deer species as well. But we don’t have any direct evidence of that until
1971 that’s the first evidence of a carcass of a badger which was proven to have
bovine tuberculosis and almost immediately after that, the farmers, the farming
lobby began to associate the risk of the disease, the threat of the disease with
the wildlife reservoir. Where as previously we had thought it had been cattle to
cattle transfer now people thought it was very likely to be badger to cattle
transfer.
(Narration)
Paul Ging:
After the carcasses of badgers left from road accidents tested
positive for TB, the badger was blamed for the spread of tuberculosis in cattle
in England. After protective legislation was passed in 1973 and again in the 80s
and 90s the badger population surged, particularly in the southwest of England
where before it was kept down by gamekeepers and farmers. In the meantime TB was
kept in check in the northwestern counties where the worst outbreaks had
occurred.
(Interview)
Prof Peter Atkins:
Bovine tuberculosis was completely eliminated from Cheshire
and from the northwestern counties which do have badger populations. So that
elimination took place in the 1950s. And what you’d expect according to the
traditional badger ecology is that bovine tuberculosis would have stayed in the
badgers which obviously weren’t culled at that time if there is an association
between the two species, but the road traffic accident data shows that that
wasn’t the case, in fact only one animal out of I think it’s 400 that were
collected over two decades in Chesire was infected with the disease, which
doesn’t suggest it was endemic in that particular county.
(Narration)
Paul Ging:
Cattle to cattle transfer of TB is still suspected to this day. In
2001 Britain was dealing with ‘foot and mouth disease’, which also led to the
massive slaughter of the country’s cattle causing farmers to bring cattle in
from elsewhere inadvertently increasing the risk of TB infection in healthy
cattle.
(Interview)
Prof Peter Atkins:
Farms needed to re-stock with fresh animals and very often
they bought those animals from the southwest which is a traditional cattle
breeding area so in County Durham for instance where quite a lot of cattle,
where slaughtered as a result of foot and mouth disease cattle were brought in
and it’s been shown that actually on several occasions those cattle brought
bovine tuberculosis with them into areas which previously hadn’t had it so this
was rather ironic. Almost certainly a proportion of the increase in bovine
tuberculosis after 2001 is the result of that restocking after foot and mouth
disease.
(Narration)
Paul Ging:
But bovine tuberculosis had spread much differently than in previous
years leading to a major outbreak in the southwest that continues to this day.
(Interview)
Prof Peter Atkins:
If you look at the European distribution of badgers they tend
to be concentrated in well the British Isles has quite a high proportion, but
especially the southwest of England has one of the highest densities of badgers
in the whole of Europe. So this spatial correlation has been made between the
tuberculosis in badgers and the tuberculosis in cattle. So there’s that debate
then between the degree of responsibility of badgers and cattle.
(Narration)
Paul Ging:
Culling badgers has recently been promoted as a means of preventing
the spread of TB, but could potentially worsen the problem if badgers are the
main carrier.
(Interview)
Prof Peter Atkins:
What was originally thought was that you’d cull the badgers
and that would prevent the spread of tuberculosis, but in fact what seems to
have happened is the exact opposite because when they are disturbed, for
instance, when they’re shot, or gassed or trapped, they seem to know something’s
going on. As a result of which is that they escape from that particular area and
move a maybe kilometre or more than a kilometre away to join other badger
groups. A likely solution to Britain’s TB problem lies in vaccination to prevent
cattle from spreading the bacterium that causes the disease in the first place,
but unfortunately vaccinating cattle for TB is forbidden by EU rules as it would
render the skin test ineffective this is because all vaccinated cattle would
then test positive for TB.
(Narration)
Paul Ging:
The search for an adequate TB vaccine for cattle continues, but
badgers can be vaccinated now to help prevent the spread of TB, an alternative
to culling. Prof Atkins recommends government take a more comprehensive approach
in controlling TB, something they have failed to do for the past century. It may
be time to learn from history.
(Interview)
Prof Peter Atkins:
Because I have historical interests and I always look at the
emergence of diseases over long periods of time my recommendation to government
would be that they should at least take note of the long history of bovine
tuberculosis and the failure of successive governments to actually intervene
successfully.
The concentration of the disease originally was in the northwest of England and
now it’s shifted to the southwest. I think that the ecology of the assumption
that badgers are always responsible for the cattle disease has got to be
reviewed.
Feb 13 2013
The more detailed report ‘Bovine tuberculosis and badgers in Britain: relevance of the past’ can be downloaded by clicking the image above.
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