Risk factors for visible lesions or positive laboratory tests in bovine tuberculosis reactor cattle in Northern Ireland

Abstract

An observational case-control study was conducted to investigate risk factors for

Risk factors for failure to detect bovine tuberculosis in cattle from infected herds across Northern Ireland (2004–2010)

“…However, our findings are not directly comparable with O'Hagan et al (2015), as for our animals to survive within our cohort to older ageclasses, they have to remain SCITT negative throughout their life, but gaining potential time at risk. All animals studied in O'Hagan et al (2015) were SCITT reactors, which would have been culled at the point of detection. Therefore, it is possible that the two studies focus on differing cohorts, each with potentially differing selective pressures.…”

“…O'Hagan et al (2015) found that for reactor animals in NI there was reduced risk of having bTB confirmed with increasing age (O'Hagan et al, 2015). However, our findings are not directly comparable with O'Hagan et al (2015), as for our animals to survive within our cohort to older ageclasses, they have to remain SCITT negative throughout their life, but gaining potential time at risk. All animals studied in O'Hagan et al (2015) were SCITT reactors, which would have been culled at the point of detection.…”

“…However, dairy herds have been found to be a risk factor for herd bTB breakdown and the risk of recurrence in Northern Ireland (Doyle et al, 2014), and of increased risk of disclosing a LRS in the Republic of Ireland (Olea-Popelka et al, 2008). O'Hagan et al (2015) looked at the probability of SCITT positive animals being confirmed with bacteriology in NI, and found that dairy herds were significantly more likely to be confirmed than non-diary. This indicates that the dairy herds may be particularly vulnerable to having SCITT tests that underperform both in their ability to detect true positives and false negatives (O'Hagan et al, 2015).…”

“…O'Hagan et al (2015) looked at the probability of SCITT positive animals being confirmed with bacteriology in NI, and found that dairy herds were significantly more likely to be confirmed than non-diary. This indicates that the dairy herds may be particularly vulnerable to having SCITT tests that underperform both in their ability to detect true positives and false negatives (O'Hagan et al, 2015). This problem of non-detection of truly infected dairy animals may be a partial explanation for the shorter times to breakdown observed in such herds in NI, as it may represent within-herd residual infection (Doyle et al, 2014;Lahuerta-Marin et al, 2015).…”

Modelling the variation in skin-test tuberculin reactions, post-mortem lesion counts and case pathology in tuberculosis-exposed cattle: Effects of animal characteristics, histories and co-infection

“…Co‐factors investigated in our models are presented in Table . We hypothesized that these variables could be influential in the antemortem test variability, confirmation or pathology, and previous research suggested that they may be important (e.g., Humblet, Boschiroli, & Saegerman, ; O'Hagan et al., ; Broughan et al., ; Downs et al., ; Shittu, Clifton‐Hadley, Ely, Upton, & Downs, ). We generated two variables to capture the movement histories of animals over their lifetime: (i) the number of herds an animal was recorded residing within over its lifetime (LOG_NUM_HERDS) and (ii) the total number of trade moves (known as market moves within the APHIS data set; LIFETIME_MARKET_MOVES) recorded for an animal over its life.…”