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Risk of tuberculosis cattle herd breakdowns in Ireland: effects of badger culling effort, density and historic large-scale interventions.

Byrne AW, White PW, McGrath G, O'Keeffe J, Martin SW - Vet. Res. (2014)

Bottom Line: In the present study, we revisit these areas to assess if there were any residual area effects of this former intervention a decade on (2007-2012).Badgers were culled in areas with higher cattle bTB risk (targeted culling).Culling badgers is not seen as a viable long-term strategy.

View Article: PubMed Central - PubMed

Affiliation: Centre for Veterinary Epidemiology and Risk Analysis, School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland. ecologicalepidemiology@gmail.com.

ABSTRACT
Bovine tuberculosis (bTB) continues to be a problem in cattle herds in Ireland and Britain. It has been suggested that failure to eradicate this disease is related to the presence of a wildlife reservoir (the badger). A large-scale project was undertaken in the Republic of Ireland during 1997-2002 to assess whether badger removal could contribute to reducing risk of cattle herd breakdowns in four areas. During the period of that "four area" study, there was a significant decrease in risk in intensively culled (removal) areas relative to reference areas. In the present study, we revisit these areas to assess if there were any residual area effects of this former intervention a decade on (2007-2012). Over the study period there was an overall declining trend in bTB breakdown risk to cattle herds. Cattle herds within former removal areas experienced significantly reduced risk of breakdown relative to herds within former reference areas or herds within non-treatment areas (OR: 0.53; P < 0.001). Increased herd breakdown risk was associated with increasing herd size (OR: 1.92-2.03; P < 0.001) and herd bTB history (OR: 2.25-2.40; P < 0.001). There was increased risk of herd breakdowns in areas with higher badger densities, but this association was only significant early in the study (PD*YEAR interaction; P < 0.001). Badgers were culled in areas with higher cattle bTB risk (targeted culling). Risk tended to decline with cumulative culling effort only in three counties, but increased in the fourth (Donegal). Culling badgers is not seen as a viable long-term strategy. However, mixed policy options with biosecurity and badger vaccination, may help in managing cattle breakdown risk.

No MeSH data available.


Related in: MedlinePlus

Mean temporal trends from a model of cattle herd breakdown risk in areas within a former large-scale badger cull trial in four counties in Ireland. Reference areas composed of farms with limited or no culling during 1997–2002; Removal areas composed of farms with intensive proactive culling during 1997–2002.
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Fig1: Mean temporal trends from a model of cattle herd breakdown risk in areas within a former large-scale badger cull trial in four counties in Ireland. Reference areas composed of farms with limited or no culling during 1997–2002; Removal areas composed of farms with intensive proactive culling during 1997–2002.

Mentions: The first model we developed concentrated on herds with land within treatment areas, using an approach similar to Griffin et al. [3]. Univariable models suggested significant associations between herd breakdown risk and all predictors (p < 0.05). Separate univariate models for the effect of former treatment on herd breakdown risk in each county found negative associations in Kilkenny (p = 0.001), Monaghan (p = 0.001) and Cork (p = 0.124), but a non-significant positive association in Co. Donegal (p = 0.922). However, in the final multivariable model, no interaction terms were significant (p > 0.1). In the final model, herds within a former removal area had 0.53 the odds of having a bTB breakdown in a given year than a herd within a former reference area (P < 0.001; Table 3). Given the very low probability of herd breakdown in Donegal, it was difficult to detect an effect (Figure 1). Cattle herd breakdown risk fluctuated significantly (Table 3) over the study period, with an overall declining trend in risk over time (Fitted linear trend: odds ratio 0.87 per year; p = 0.004). Herd risk was significantly increased for herds that had a previous herd breakdown in comparison with herd that didn’t (OR: 2.250; p < 0.001), and with increasing herd size (log(herdsize) OR: 2.034; p < 0.001). Kilkenny herds had the overall greatest risk of having a breakdown, followed by Cork, Monaghan, and Donegal (Figure 1; Table 3).Table 3


Risk of tuberculosis cattle herd breakdowns in Ireland: effects of badger culling effort, density and historic large-scale interventions.

Byrne AW, White PW, McGrath G, O'Keeffe J, Martin SW - Vet. Res. (2014)

Mean temporal trends from a model of cattle herd breakdown risk in areas within a former large-scale badger cull trial in four counties in Ireland. Reference areas composed of farms with limited or no culling during 1997–2002; Removal areas composed of farms with intensive proactive culling during 1997–2002.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4230509&req=5

Fig1: Mean temporal trends from a model of cattle herd breakdown risk in areas within a former large-scale badger cull trial in four counties in Ireland. Reference areas composed of farms with limited or no culling during 1997–2002; Removal areas composed of farms with intensive proactive culling during 1997–2002.
Mentions: The first model we developed concentrated on herds with land within treatment areas, using an approach similar to Griffin et al. [3]. Univariable models suggested significant associations between herd breakdown risk and all predictors (p < 0.05). Separate univariate models for the effect of former treatment on herd breakdown risk in each county found negative associations in Kilkenny (p = 0.001), Monaghan (p = 0.001) and Cork (p = 0.124), but a non-significant positive association in Co. Donegal (p = 0.922). However, in the final multivariable model, no interaction terms were significant (p > 0.1). In the final model, herds within a former removal area had 0.53 the odds of having a bTB breakdown in a given year than a herd within a former reference area (P < 0.001; Table 3). Given the very low probability of herd breakdown in Donegal, it was difficult to detect an effect (Figure 1). Cattle herd breakdown risk fluctuated significantly (Table 3) over the study period, with an overall declining trend in risk over time (Fitted linear trend: odds ratio 0.87 per year; p = 0.004). Herd risk was significantly increased for herds that had a previous herd breakdown in comparison with herd that didn’t (OR: 2.250; p < 0.001), and with increasing herd size (log(herdsize) OR: 2.034; p < 0.001). Kilkenny herds had the overall greatest risk of having a breakdown, followed by Cork, Monaghan, and Donegal (Figure 1; Table 3).Table 3

Bottom Line: In the present study, we revisit these areas to assess if there were any residual area effects of this former intervention a decade on (2007-2012).Badgers were culled in areas with higher cattle bTB risk (targeted culling).Culling badgers is not seen as a viable long-term strategy.

View Article: PubMed Central - PubMed

Affiliation: Centre for Veterinary Epidemiology and Risk Analysis, School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland. ecologicalepidemiology@gmail.com.

ABSTRACT
Bovine tuberculosis (bTB) continues to be a problem in cattle herds in Ireland and Britain. It has been suggested that failure to eradicate this disease is related to the presence of a wildlife reservoir (the badger). A large-scale project was undertaken in the Republic of Ireland during 1997-2002 to assess whether badger removal could contribute to reducing risk of cattle herd breakdowns in four areas. During the period of that "four area" study, there was a significant decrease in risk in intensively culled (removal) areas relative to reference areas. In the present study, we revisit these areas to assess if there were any residual area effects of this former intervention a decade on (2007-2012). Over the study period there was an overall declining trend in bTB breakdown risk to cattle herds. Cattle herds within former removal areas experienced significantly reduced risk of breakdown relative to herds within former reference areas or herds within non-treatment areas (OR: 0.53; P < 0.001). Increased herd breakdown risk was associated with increasing herd size (OR: 1.92-2.03; P < 0.001) and herd bTB history (OR: 2.25-2.40; P < 0.001). There was increased risk of herd breakdowns in areas with higher badger densities, but this association was only significant early in the study (PD*YEAR interaction; P < 0.001). Badgers were culled in areas with higher cattle bTB risk (targeted culling). Risk tended to decline with cumulative culling effort only in three counties, but increased in the fourth (Donegal). Culling badgers is not seen as a viable long-term strategy. However, mixed policy options with biosecurity and badger vaccination, may help in managing cattle breakdown risk.

No MeSH data available.


Related in: MedlinePlus