Northern Ireland farm-level management factors for prolonged bovine tuberculosis herd breakdowns.

Publication history: Accepted - 16 September 2020; Published online - 28 September 2020This study determined farm management factors associated with long-duration bovine tuberculosis (bTB) breakdowns disclosed in the period 23 May 2016 to 21 May 2018; a study area not previously subject to investigation in Northern Ireland. A farm-level epidemiological investigation (n = 2935) was completed when one or more Single Intradermal Comparative Cervical Test (SICCT) reactors or when one or more confirmed (positive histological and/or bacteriological result) lesion at routine slaughter were disclosed. A case-control study design was used to construct an explanatory set of management factors associated with long-duration bTB herd breakdowns; with a case (n = 191) defined as an investigation into a breakdown of 365 days or longer. Purchase of infected animal(s) had the strongest association as the most likely source of infection for long-duration bTB herd breakdowns followed by badgers and then cattle-to-cattle contiguous herd spread. However, 73.5% (95% CI 61.1–85.9%) of the herd type contributing to the purchase of infection source were defined as beef fattening herds. This result demonstrates two subpopulations of prolonged bTB breakdowns, the first being beef fattening herds with main source continuous purchase of infected animals and a second group of primary production herds (dairy, beef cows and mixed) with risk from multiple sources

Effect of selective removal of badgers (Meles meles) on ranging behaviour during a ‘Test and Vaccinate or Remove’ intervention in Northern Ireland

Publication history: Accepted - 23 April 2021; Published online - 7 May 2021The role of the Eurasian badger (Meles meles) as a wildlife host has complicated the management of bovine tuberculosis (bTB) in cattle. Badger ranging behaviour has previously been found to be altered by culling of badgers and has been suggested to increase the transmission of bTB either among badgers or between badgers and cattle. In 2014, a five-year bTB intervention research project in a 100 km2 area in Northern Ireland was initiated involving selective removal of dual path platform (DPP) VetTB (immunoassay) test positive badgers and vaccination followed by release of DPP test negative badgers (‘Test and Vaccinate or Remove’). Home range sizes, based on position data obtained from global positioning system collared badgers, were compared between the first year of the project, where no DPP test positive badgers were removed, and follow-up years 2–4 when DPP test positive badgers were removed. A total of 105 individual badgers were followed over 21 200 collar tracking nights. Using multivariable analyses, neither annual nor monthly home ranges differed significantly in size between years, suggesting they were not significantly altered by the bTB intervention that was applied in the study area.This research was funded by the Department of Agriculture, Environment and Rural Affairs for Northern Ireland

Bovine tuberculosis in Northern Ireland : Surveillance, Biosecurity and Farmers' Attitudes

Bovine tuberculosis (bTB), caused by Mycobacterium bovis, has a global distribution and is one of the most important infectious diseases affecting the cattle industry in Northern Ireland. Although it primarily affects cattle, other mammals including humans can be infected as well. A compulsory eradication programme based on testing and removal of positive animals has been in place since 1959 in Northern Ireland. However, bTB still persists in the cattle population due to a variety of reasons including residual infection within the herd, recurrent infection of herds and persistence of infection in the locality. This thesis aimed to address some of these problems focussing on surveillance, biosecurity and farmers’ attitudes in relation to bTB control. The main issues considered included: the imperfect sensitivity of the currently available diagnostic tests the little sense of ownership by farmers in relation to bTB control the nature of the farming industry in Northern Ireland the presence of a wildlife reservoir (European badger, Meles meles) Surveillance for bTB in Northern Ireland is mainly based on a combination of the single intradermal comparative cervical tuberculin (SICCT) test and routine post-mortem examination. Estimation of diagnostic test characteristics showed that both tests were found to have a near perfect specificity but the reported sensitivity was not for either test resulting in the potential of leaving infected animals behind. Residual infection was found to be linked to the number of SICCT test reactors disclosed during the bTB breakdown with breakdowns with multiple reactors especially being a risk factor for future bTB breakdown regardless of the confirmation status of the breakdown. Focusing on post-mortem inspection, potential risk factors that affect the development of visible bTB lesions in SICCT test reactors were evaluated and disclosed creating more vigilance during the post mortem examination of animals in specific categories. In Northern Ireland and the rest of the British Isles, all aspects of the bTB eradication programme are currently controlled by Government resulting in a lack of direct involvement of the farming industry. This thesis sets a baseline level as to what farmers’ current attitudes are towards bTB control and bTB related biosecurity in Northern Ireland. There was a lack of adoption of bTB related biosecurity measures by farmers, especially in relation to badgers. Furthermore risk factors for bTB breakdown at the farm management level were disclosed including the presence of accessible badger setts, the observation of live badgers on the farm and feeding magnesium supplement and meal on top of the silage. The potential for nose-to-nose contact and therefore bTB transmission between cattle of neighbouring herds was also found to be cause for concern. In conclusion, bTB in cattle is a complex disease with many challenges still to be faced. However, this thesis has aimed to address some of these difficulties, which are hoped to contribute, along with further research, to further control and ultimately eradication of bTB in Northern Ireland

Bovine tuberculosis in Northern Ireland : Surveillance, Biosecurity and Farmers' Attitudes

Bovine tuberculosis (bTB), caused by Mycobacterium bovis, has a global distribution and is one of the most important infectious diseases affecting the cattle industry in Northern Ireland. Although it primarily affects cattle, other mammals including humans can be infected as well. A compulsory eradication programme based on testing and removal of positive animals has been in place since 1959 in Northern Ireland. However, bTB still persists in the cattle population due to a variety of reasons including residual infection within the herd, recurrent infection of herds and persistence of infection in the locality. This thesis aimed to address some of these problems focussing on surveillance, biosecurity and farmers’ attitudes in relation to bTB control. The main issues considered included: the imperfect sensitivity of the currently available diagnostic tests the little sense of ownership by farmers in relation to bTB control the nature of the farming industry in Northern Ireland the presence of a wildlife reservoir (European badger, Meles meles) Surveillance for bTB in Northern Ireland is mainly based on a combination of the single intradermal comparative cervical tuberculin (SICCT) test and routine post-mortem examination. Estimation of diagnostic test characteristics showed that both tests were found to have a near perfect specificity but the reported sensitivity was not for either test resulting in the potential of leaving infected animals behind. Residual infection was found to be linked to the number of SICCT test reactors disclosed during the bTB breakdown with breakdowns with multiple reactors especially being a risk factor for future bTB breakdown regardless of the confirmation status of the breakdown. Focusing on post-mortem inspection, potential risk factors that affect the development of visible bTB lesions in SICCT test reactors were evaluated and disclosed creating more vigilance during the post mortem examination of animals in specific categories. In Northern Ireland and the rest of the British Isles, all aspects of the bTB eradication programme are currently controlled by Government resulting in a lack of direct involvement of the farming industry. This thesis sets a baseline level as to what farmers’ current attitudes are towards bTB control and bTB related biosecurity in Northern Ireland. There was a lack of adoption of bTB related biosecurity measures by farmers, especially in relation to badgers. Furthermore risk factors for bTB breakdown at the farm management level were disclosed including the presence of accessible badger setts, the observation of live badgers on the farm and feeding magnesium supplement and meal on top of the silage. The potential for nose-to-nose contact and therefore bTB transmission between cattle of neighbouring herds was also found to be cause for concern. In conclusion, bTB in cattle is a complex disease with many challenges still to be faced. However, this thesis has aimed to address some of these difficulties, which are hoped to contribute, along with further research, to further control and ultimately eradication of bTB in Northern Ireland