David ramsey daniel o brien rick smith melinda cosgrove james averill stephen schmitt brent rudolph
Download
1 / 41

Spatial model of bTB in WTD in DMU452 - PowerPoint PPT Presentation


  • 74 Views
  • Uploaded on

Management of on-farm risk to livestock from bovine TB in white-tailed deer within Deer Management Unit 452: Predictions from a spatially-explicit model. David Ramsey, Daniel O’Brien, Rick Smith , Melinda Cosgrove, James Averill , Stephen Schmitt, Brent Rudolph.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Spatial model of bTB in WTD in DMU452 ' - teddy


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
David ramsey daniel o brien rick smith melinda cosgrove james averill stephen schmitt brent rudolph

Management of on-farm risk to livestock from bovine TB in white-tailed deer within Deer Management Unit 452:Predictions from a spatially-explicit model

David Ramsey, Daniel O’Brien, Rick Smith, Melinda Cosgrove, James Averill, Stephen Schmitt, Brent Rudolph


Spatial model of btb in wtd in dmu452
Spatial model of bTB in WTD in DMU452 white-tailed deer within Deer Management Unit 452:

  • Recent development of a spatial model of TB in WTD has examined the efficacy of management options for DMU452 [Ramsey et al. 2014. J. Wildl. Manage 78(2):240-254.]

  • Modelled scenarios included

    • Increase in harvest

    • Vaccination

    • Increase in harvest + vaccination

    • The effect of baiting

  • All scenarios were examined as to their efficacy to eradication of TB from WTD within 30 years


  • Findings from the deer tb model
    Findings from the deer TB model white-tailed deer within Deer Management Unit 452:

    • Current MDNR management is unlikely to eradicate TB over the next three decades

    • Eradication is possible within three decades, but is likely to require substantial increases in current harvest and/or vaccination

    • TB establishment in a previously TB-free region is ~8 times more likely if baiting occurs during the hunting season

    • In the meantime, cattle on farms within DMU 452 continue to be at-risk of TB infection from WTD


    The way forward
    The way forward? white-tailed deer within Deer Management Unit 452:

    • If complete eradication of TB from WTD is too difficult, should focus change to risk mitigation for livestock?

    • Acceptable management options may exist that will minimize risk of on-farm transmission from WTD to livestock

    • Extend current spatial model to include transmission of TB from WTD to livestock


    Modelling livestock transmission
    Modelling livestock transmission white-tailed deer within Deer Management Unit 452:

    • A spatial “livestock” layer was created for the existing model using records from the Michigan Department of Agriculture & Rural Development

      • Farm location

      • Area of cleared pasture

      • Stocking rate

    • Data on the TB cattle herd infection (aka breakdown) rate 2003 – 2012 was also collated and used to calibrate transmission

    • TB transmission dependent on stocking rate and contact rate with infected WTD


    Dmu 452 farm locations their relative areas
    DMU 452, farm locations & their relative areas white-tailed deer within Deer Management Unit 452:


    Mean cattle herd infection rate year vs predicted
    Mean cattle herd infection rate/year vs predicted white-tailed deer within Deer Management Unit 452:


    On farm risk by location no mitigation
    On-farm risk by location (no mitigation) white-tailed deer within Deer Management Unit 452:

    High risk

    Mod risk

    Low risk


    Effect of management on transmission to livestock
    Effect of management on transmission to livestock white-tailed deer within Deer Management Unit 452:

    • Evaluate effects of various management options on the risk of transmission to livestock (herd infections/breakdowns)

    • Management of WTD within DMU452

      • Increasing harvest rate

      • Vaccination

      • Increase harvest + vaccination

    • On-farm management practices

      • Restricting contact between WTD and cattle on farms

      • Local WTD control in the vicinity of farms

    • Scenarios examined with and without baiting



    Increasing harvest rates

    100 infection rates on farms

    80

    60

    40

    20

    0

    Antlered

    Antlerless

    Increasing harvest rates

    2x

    2x

    Multiple of current harvest

    Harvest rate

    1.5x

    1.25x

    3x

    current

    2x

    1.5x

    1.25x

    current

    3

    1

    2

    4

    1

    2

    3

    4

    Scenarios


    Effects of increasing harvest on hb with baiting
    Effects of increasing harvest on HB (with baiting) infection rates on farms

    Antler

    Antlerless

    1.25x 1.25x

    1.5x 1.5x

    2.0x 2.0x

    2.0x 3.0x


    Effects of increasing harvest on hb no baiting
    Effects of increasing harvest on HB (no baiting) infection rates on farms

    Antler

    Antlerless

    1.25x 1.25x

    1.5x 1.5x

    2.0x 2.0x

    2.0x 3.0x


    Harvest 90 vaccinated annually with baiting
    Harvest + 90% vaccinated annually (with baiting) infection rates on farms

    Antler

    Antlerless

    1.25x 1.25x

    1.5x 1.5x

    2.0x 2.0x

    2.0x 3.0x


    Harvest 90 vaccinated annually no baiting
    Harvest + 90% vaccinated annually (no baiting) infection rates on farms

    Antler

    Antlerless

    1.25x 1.25x

    1.5x 1.5x

    2.0x 2.0x

    2.0x 3.0x


    Vaccination only with baiting
    Vaccination only (with baiting) infection rates on farms


    Vaccination only no baiting
    Vaccination only (no baiting) infection rates on farms


    Effect of on-farm management infection rates on farms


    Restriction of contact between wtd and cattle
    Restriction of contact between WTD and cattle infection rates on farms

    • Baseline model assumes unrestricted contact between WTD and cattle on farms

    • Examined the effect of restricting contact on cattle herd infections

    • Practically this can be achieved (for example) by

      • Improved fencing

      • Restricting access to food sources


    On farm contact reduction
    On-farm contact reduction (%) infection rates on farms

    No reduction

    High risk

    Mod risk

    Low risk


    On farm contact reduction1
    On-farm contact reduction (%) infection rates on farms

    20% reduction

    High risk

    Mod risk

    Low risk


    On farm contact reduction2
    On-farm contact reduction (%) infection rates on farms

    50% reduction

    High risk

    Mod risk

    Low risk


    On farm contact reduction3
    On-farm contact reduction (%) infection rates on farms

    80% reduction

    High risk

    Mod risk

    Low risk


    On farm contact reduction4
    On-farm contact reduction (%) infection rates on farms

    90% reduction

    High risk

    Mod risk

    Low risk


    Local control of wtd
    Local control of WTD infection rates on farms

    • Manage WTD in the vicinity of farms only

    • Less expensive option than management of deer across the entire DMU

    • What size buffer would be adequate to achieve significant reduction in herd infections?





    An aside if prevalence in deer has gone down why are cattle herds still getting infected
    An aside: If prevalence in deer has gone down, why are cattle herds still getting infected?

    • Speculation that because cattle herds are still becoming infected, there must be some wild species (other than deer) infecting cattle

    • At least two existing lines of evidence argue against such speculation

      • Modelling

      • Spatial variations in deer prevalence


    Effects of increasing harvest on hb with baiting1
    Effects of increasing harvest on HB (with baiting) cattle herds still getting infected?

    Antler

    Antlerless

    1.25x 1.25x

    1.5x 1.5x

    2.0x 2.0x

    2.0x 3.0x

    Deer prevalence:

    ~0.7%

    ~4 years

    ~4 years

    Figure 3A, Ramsey et al., 2014, J. Wildl. Mgt. 78(2):245.


    Effects of increasing harvest on hb with baiting2
    Effects of increasing harvest on HB (with baiting) cattle herds still getting infected?

    Antler

    Antlerless

    1.25x 1.25x

    1.5x 1.5x

    2.0x 2.0x

    2.0x 3.0x

    Deer prevalence:

    ~0.6%

    ~8 years

    ~8 years

    Figure 3A, Ramsey et al., 2014, J. Wildl. Mgt. 78(2):245.


    Effects of increasing harvest on hb with baiting3
    Effects of increasing harvest on HB (with baiting) cattle herds still getting infected?

    Antler

    Antlerless

    1.25x 1.25x

    1.5x 1.5x

    2.0x 2.0x

    2.0x 3.0x

    Deer prevalence:

    ~1.1%

    30 years

    Figure 3A, Ramsey et al., 2014, J. Wildl. Mgt. 78(2):245.


    Effects of increasing harvest on hb with baiting4
    Effects of increasing harvest on HB (with baiting) cattle herds still getting infected?

    Antler

    Antlerless

    1.25x 1.25x

    1.5x 1.5x

    2.0x 2.0x

    2.0x 3.0x

    Deer prevalence:

    ~0.05%

    ~18 years

    ~18 years

    Figure 3A, Ramsey et al., 2014, J. Wildl. Mgt. 78(2):245.


    Tb prevalence in deer varies locally
    TB prevalence in deer varies locally cattle herds still getting infected?

    2003

    29N 6E: 3.0%

    DMU452: 1.7%


    Tb prevalence in deer varies locally1
    TB prevalence in deer varies locally cattle herds still getting infected?

    2003

    29N 6E: 3.0%

    DMU452: 1.7%

    2006

    31N 5E: 3.1%

    DMU452: 2.3%

    2006

    30N 5E: 4.9%

    DMU452: 2.3%


    Tb prevalence in deer varies locally2
    TB prevalence in deer varies locally cattle herds still getting infected?

    2003

    29N 6E: 3.0%

    DMU452: 1.7%

    2006

    31N 5E: 3.1%

    DMU452: 2.3%

    2006

    30N 5E: 4.9%

    DMU452: 2.3%

    2012

    27N 5E: 5.6%

    DMU452: 1.7%


    The future predicting local variations in tb prevalence
    The future: predicting local variations in TB prevalence cattle herds still getting infected?


    Conclusions dmu wide control
    Conclusions (DMU wide control) cattle herds still getting infected?

    • Compared with TB control in WTD directly, management aimed at reduction of cattle herd infections requires much less effort ($)

    • But… management needs to continue in perpetuity as TB remains in the wider deer population

      • Gains will be rapidly lost once management ceases (e.g. lifting of baiting bans)

    • A 25% increase in harvest and no baiting would halve the rate of cattle herd infections within 3-5 years and reduce it by 95% within 15 years

    • Vaccination each year achieving 50% coverage would also achieve the same result


    Conclusions farm level control
    Conclusions (farm level control) cattle herds still getting infected?

    • Substantial reduction in the risk of herd infections is achieved if contact between WTD and cattle on farms is reduced by at least 80%

    • Local control measures can also be effective

      • Vaccinating at least 50% of WTD within 5 km of farms will reduce the cattle herd infection rate by 95% within 13 years

      • Culling 50% of deer in addition to harvest within the 5 km buffer would reduce the herd infection rate by 95% within 10 years


    Conclusions
    Conclusions cattle herds still getting infected?

    • That cattle herd infections continue to occur annually despite reductions in TB in deer is expected, and consistent both with modeled predictions and what we already know about TB in deer

    • Results suggest that without effective wildlife risk mitigation, TB prevalence in deer at the DMU452 scale will need to be maintained well below 1% before cattle herd infections do not consistently occur every year, and well below 0.1% before there is a high probability of having no annual cattle herd infections


    Thank you
    Thank you cattle herds still getting infected?


    ad