Dáil Éireann Debate, Thursday - 2 March 2023
317. Deputy Jackie Cahill asked the Minister for Agriculture, Food and the Marine the number of TB lesions that were cultured in 2022; the percentage of these lesions that were from reactor animals; the percentage that were from post-mortems in factories; if he will provide a ratio of positive to negative cultures; and if he will make a statement on the matter. [10695/23]
View answerWhen cattle are slaughtered as reactors under the TB eradication programme, it is because they have tested positive for infection with TB. It is not routine to culture all TB reactors.
In 2022, 23,393 (provisional figure) cattle have been slaughtered as reactors under the TB eradication programme, as they are deemed to be infected with the TB disease agent. The test specificity is estimated at 99.98%, meaning the number of false positives to the skin test is estimated at one animal in 5,000 tested.
However, the skin test has an estimated sensitivity of 80% which means that approximately one in five animals infected with TB will not be identified by the test, on average. This means that false negatives are much more problematic for the TB programme than false positives.
Visual inspection of reactor carcasses at post-mortem finds that, on average, approximately 30% of such reactors have visible lesions of tuberculosis, meaning the infection has progressed to a stage where the disease process has caused such significant tissue damage that it can be seen with the naked eye.
If a reactor does not have visible disease lesions, it does not mean it is not infected; visual inspection cannot detect the presence of microscopic lesions and bacteria within the tissues of such animals.
Separately from the slaughter of TB reactors, all non-TB reactor cattle routinely slaughtered in Ireland are subjected to a post-mortem veterinary inspection which includes surveillance for lesions suspected to be caused by TB.
In 2022, approximately 4,600 such suspect lesions were identified and of these, approximately 55% are subsequently found by laboratory testing (combination of histological examination and/or culture) to have been caused by TB. The herds from which those animals came are then subjected to follow-up testing to identify any other undetected infected cattle.
