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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

The relationship between cattle herds breakdown risk and badger culling intensity, modelled using splines. Herds exposed to culling are generally higher risk herds relative to herd away from culled areas. Risk declines with increased culling intensity in Counties Cork, Kilkenny and Monaghan, whereas risk increases with culling intensity in Co. Donegal.
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Fig3: The relationship between cattle herds breakdown risk and badger culling intensity, modelled using splines. Herds exposed to culling are generally higher risk herds relative to herd away from culled areas. Risk declines with increased culling intensity in Counties Cork, Kilkenny and Monaghan, whereas risk increases with culling intensity in Co. Donegal.

Mentions: Cattle herd breakdown risk was lower for farms in previous removal areas relative to reference areas (OR: 0.53; P < 0.001) and relative to non-treatment farms (OR: 0.53; P < 0.001). There was no significant difference in risk between farms in reference and non-treatment areas (OR: 1.00; P = 0.976). A history of bTB breakdowns (OR: 2.40; P < 0.001) and increasing herd size (OR: 1.92; P < 0.001) increased the risk of herd breakdown. Overall, there was a significant declining trend in herd risk across the study population during the study period (fitted linear trend: odds ratio 0.89 per year; p < 0.001). However, the effect of PD on herd risk varied significantly depending on year (PD*YEAR: P < 0.001). Early in the study there was an increased risk of bTB breakdown with increasing PD (Figure 2A); similarly, the reduction in risk over time was mainly gained from reducing the risk in high badger density areas (Figure 2B). The effect of targeted badger culling on herd breakdown risk had a curvilinear form (see Additional file 2), with significant increased risk of breakdown risk for herds exposed to culling relative to herds without culling (CULL spline 1: OR: 3.220). There was a significant interaction between the second spline of CULL and county; resulting in decreased risk in Monaghan, Kilkenny and Cork but an increased risk in Donegal (overall CULL spline 2*COUNTY: P < 0.001; Table 6; Figure 3).Figure 2


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)

The relationship between cattle herds breakdown risk and badger culling intensity, modelled using splines. Herds exposed to culling are generally higher risk herds relative to herd away from culled areas. Risk declines with increased culling intensity in Counties Cork, Kilkenny and Monaghan, whereas risk increases with culling intensity in Co. Donegal.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig3: The relationship between cattle herds breakdown risk and badger culling intensity, modelled using splines. Herds exposed to culling are generally higher risk herds relative to herd away from culled areas. Risk declines with increased culling intensity in Counties Cork, Kilkenny and Monaghan, whereas risk increases with culling intensity in Co. Donegal.
Mentions: Cattle herd breakdown risk was lower for farms in previous removal areas relative to reference areas (OR: 0.53; P < 0.001) and relative to non-treatment farms (OR: 0.53; P < 0.001). There was no significant difference in risk between farms in reference and non-treatment areas (OR: 1.00; P = 0.976). A history of bTB breakdowns (OR: 2.40; P < 0.001) and increasing herd size (OR: 1.92; P < 0.001) increased the risk of herd breakdown. Overall, there was a significant declining trend in herd risk across the study population during the study period (fitted linear trend: odds ratio 0.89 per year; p < 0.001). However, the effect of PD on herd risk varied significantly depending on year (PD*YEAR: P < 0.001). Early in the study there was an increased risk of bTB breakdown with increasing PD (Figure 2A); similarly, the reduction in risk over time was mainly gained from reducing the risk in high badger density areas (Figure 2B). The effect of targeted badger culling on herd breakdown risk had a curvilinear form (see Additional file 2), with significant increased risk of breakdown risk for herds exposed to culling relative to herds without culling (CULL spline 1: OR: 3.220). There was a significant interaction between the second spline of CULL and county; resulting in decreased risk in Monaghan, Kilkenny and Cork but an increased risk in Donegal (overall CULL spline 2*COUNTY: P < 0.001; Table 6; Figure 3).Figure 2

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