Genetic Predisposition to Pass the Standard SICCT Test for Bovine
Tuberculosis in British Cattle |
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Authors: | William Amos Ellen Brooks-Pollock Ruth Blackwell Erin Driscoll Martha Nelson-Flower Andrew J K Conlan |
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Institution: | 1. Department of Zoology, Cambridge University,
Cambridge, Cambridgeshire, United Kingdom.; 2. Department of Veterinary Medicine Disease
Dynamics Unit, Cambridge University, Cambridge, Cambridgeshire, United
Kingdom.; 3. Animal Health and Veterinary Laboratories
Agency (AHVLA), New Haw, Addlestone, Surrey, United Kingdom.; University of Ottawa, Canada, |
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Abstract: | Bovine tuberculosis (bTB) imposes an important financial burden on the British
cattle industry, yet despite intense efforts to control its spread, incidence is
currently rising. Surveillance for bTB is based on a skin test that measures an
immunological response to tuberculin. Cattle that fail the test are classified
as “reactors” and slaughtered. Recent studies have identified
genetic markers associated with the reaction of cattle to the tuberculin test.
At marker INRA111 a relatively common ‘22’ genotype occurs
significantly more frequently in non-reactor cattle. Here we test the
possibility that the putative protective ‘22’ genotype does not
confer resistance but instead causes cattle that carry it to react less strongly
to the prescribed test, and hence avoid slaughter, potentially even though they
are infected. We show that, after controlling for age and breed,
‘22’ cattle react less strongly to the immunological challenge and
may therefore be less likely to be classified as a reactor. These results
highlight the potential discrepancy between infection and test status and imply
that the effectiveness of the test-and-slaughter policy may be being compromised
by selection for cattle that are genetically predisposed to react less strongly
to tuberculin. |
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