TB PREVALENCE - DEFRA'S BADGER ROAD TRAFFIC ACCIDENT SURVEY
3 Aug 2005 01:15 PM
Data from Defra's badger Road Traffic Accident survey (RTA), covering
the three years 2002 - 2004, has been published today.
The study was based on TB tests carried out on road kill badgers
collected from seven counties. It found that, on average, around one
in seven was diseased.
The RTA survey, carried out on the advice of, and supervised by, the
Independent Scientific Group on Cattle TB (ISG), was designed to
establish whether the level of bovine TB infection in dead badgers,
collected from road accidents, reflected disease prevalence in the
badger population in the area. This was done by comparing data with
findings from the Randomised Badger Culling Trial (RBCT).
The survey was carried out in the RBCT counties of Cornwall, Devon,
Gloucestershire, Herefordshire, and Worcestershire. Shropshire and
Dorset were also targeted as comparison counties.
The data collected can be used to estimate prevalence at county
level. In general, the prevalence of M. Bovis infection in badgers
was higher in the northern group of counties involved
(Gloucestershire, Herefordshire, Shropshire and Worcestershire) than
those in the southern group (Cornwall, Devon and Dorset).
However, not enough badgers were collected through the RTA survey to
allow parish-level prevalence estimates to be made. This is a clear
limitation of the RTA survey. Even at a county level, for reasons
such as the imprecise nature of diagnostic tests and the limited
number of badgers collected, the ISG advises it is best to interpret
the prevalence estimates relatively rather than absolutely.
Animal Health Minister Ben Bradshaw welcomed the publication of the
data. He said: "These findings show that even in those parts of the
country worst affected by bovine TB, most badgers test negative for
the disease. They also show no clear correlation between the levels
of TB in cattle and badgers.
"These latest findings will be used alongside other research and
advice from the UK and abroad to develop policy on tackling bovine
TB."
NOTES FOR EDITORS
1. The data reported here only included badgers found dead by the
roadside in the seven specific counties. Data from other badgers
collected e.g. those found dead on farms away from roads but within
Randomised Badger Culling Trial (RBCT) areas, or in RBCT areas
outside the seven counties, were excluded from the analysis used to
produce these results.
2. The most recent figures show an overall prevalence of M. Bovis in
the RTA badgers of 0.17 in 2002 (95% Confidence Interval (CI) of 0.14
to 0.21), 0.13 in 2003 (95% CI: 0.10 to 0.15) and 0.15 in 2004 (95%
CI: 0.13 to 0.18).
3. The results of the analysis of 2002 - 2004 RTA data can be found
at:
http://www.defra.gov.uk/animalh/tb/index.htm
http://www.defra.gov.uk/animalh/tb/publications/index.htm#rta
http://www.defra.gov.uk/animalh/tb/isg/publicationlist.htm#rta
Note that some map symbols may appear on top of each other and
therefore it is difficult to estimate regional prevalence precisely
by eye; for prevalence, see the ISG data referred to above.
4. The ISG has advised that it is a fundamental principle of
scientific trials that data must not be released prematurely since
that could compromise the subsequent integrity of the trials and that
no data should be released from the RBCT trial areas which could
discourage farmers' willingness to participate in the RBCT, or
encourage either illegal killing of badgers or interference with RBCT
operations. For this reason, data on results of culture for M. Bovis
from individual badgers in trial areas have not been released.
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