Question
(4) how many cattle herds were tested for bovine tuberculosis in the last 12 months for which figures are available; and in what percentage of those herds at least one cow tested positive.
Answer
[holding answer 5 July 2010]: An effective TB testing audit process has already been drawn up and used to audit Animal Health staff engaged in TB testing. Consideration is currently being given as to how best to extend the audit process to all TB testers on an ongoing basis.The tuberculin skin test has a specificity of 99.9%, which means that when applied to cattle without TB in Great Britain, there is a one in 1,000 chance that a non-infected animal will be wrongly classified as a reactor. The probability of false positives is therefore 0.1%.A failure to detect lesions of TB through post-mortem inspections or to culture M.bovis (the causative organism of the disease) in the laboratory does not imply that a test reactor was not infected with bovine TB. In the early stages of the disease it is not always possible to observe lesions during post-mortem examination and, due to the fastidious nature of this organism it is very difficult to isolate it from tissue samples without lesions. The primary purpose of post mortem inspections and culture is not to establish the presence or absence of disease, but rather to identify the severity and strain of infection. It is therefore not possible to say what percentage of cattle slaughtered following positive bovine tuberculosis tests are found to be free of tuberculosis when tested after slaughter.During the last 12 months 42,262 cattle herds that were not under movement restrictions were tested for bovine Tuberculosis in England. Of these herds 7.9% had at least one animal test positive."Notes:""Data from Vetnet is produced three months in arrears and the latest report available is for March 2010. Therefore data cannot be provided for the last three months.""Data from Vetnet is provisional and subject to change as more data becomes available.""Source:""Vetnet—Animal Health Database"