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ANNEX 3 (b) Epidemiological scenarios results
Table 3.1. Proportion (%) of replicates for which there was an increase in the number of infected holdings.
- Results are based on one hundred replicates of the model for each incursion/control scenario.
- The results show the proportion (%) of replicates for which there was any increase in the number of infected holdings, not just major outbreaks.
- Within each incursion scenario there were no significant ( P>0.05) differences between control scenarios in the proportion of replicates for which there was an increase in the number of infected holdings.
Incursion Scenario Control Scenario | a. Northwards spread - July 08 | b. Northwards spread - Sept. 08 | c. Northwards spread - April 09 | d. Animal import - Sept. 08 | e. Animal import - April 09 |
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1. do nothing beyond the minimum requirements | 50 | 3 | 8 | 28 | 17 |
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2. vaccinate 100% of holdings in a border PZ | 40 | 4 | 14 | 30 | 12 |
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3. vaccinate 80% of holdings in a PZ to the Highland B/F line | 52 | 5 | 9 | 24 | 14 |
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4. vaccinate 50% of holdings in a PZ comprising the whole of Scotland | 54 | 5 | 11 | 18 | 9 |
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5. vaccinate 80% of holdings in a 100km PZ around the first affected holding (only if the incursion occurs above the Highland B/F line) | NA | NA | NA | 22 | NA |
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Table 3.2. Mean, 2.5th and 97.5th percentiles for the cumulative number of infected holdings at the end of year two of the simulations.
- Results are based on one hundred replicates of the model for each incursion/control scenario.
- The first number gives the mean and the numbers in brackets give the 2.5th and 97.5th percentiles for the cumulative number of infected holdings at the end of year two of the simulations.
Incursion Scenario Control Scenario | a. Northwards spread - July 08 | b. Northwards spread - Sept. 08 | c. Northwards spread - April 09 | d. Animal import - Sept. 08 | e. Animal import - April 09 |
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1. do nothing beyond the minimum requirements | 874.3 (1-8816) | 45.9 † (1-39.5) | 303.8 (1-3728.5) | 1117.0 (1-10522) | 1447.3 (1-14353) |
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2. vaccinate 100% of holdings in a border PZ | 19.8 (1-46) | 3.9 (1-21) | 3.5 (1-16) | 35.6 (1-357.5) | 3.1 (1-25.5) |
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3. vaccinate 80% of holdings in a PZ to the Highland B/F line | 25.5 (1-89) | 12.0 (1-25.5) | 3.2 (1-11) | 33.3 (1-467.5) | 3.2 (1-23) |
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4. vaccinate 50% of holdings in a PZ comprising the whole of Scotland | 21.5 (1-103) | 7.9 (1-19.5) | 3.2 (1-14.5) | 17.7 (1-186) | 2.5 (1-22.5) |
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5. vaccinate 80% of holdings in a 100km PZ around the first affected holding (only if the incursion occurs above the Highland B/F line) | NA | NA | NA | 2.1 (1-168.5) | NA |
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† the high mean (relative to the 97.5th percentile) for this scenario is a consequence of one large outbreak (4064 infected farms)
Table 3.3. Proportion (%) of replicates for which infection had died out within the two-year time period of the simulations.
- Results are based on one hundred replicates of the model for each incursion/control scenario.
- This table includes only those replicates for which there was an increase in the number of infected holdings (see Table 3.1).
- Within each control scenario there were no significant ( P>0.05) differences amongst incursion scenarios in the proportion of replicates dying out. However, the proportion of replicates dying out was significantly ( P<0.05) higher for all vaccination strategies (control scenarios 2-5) compared with that in which only the minimal requirements were implemented (control scenario 1).
Incursion Scenario Control Scenario | a. Northwards spread - July 08 | b. Northwards spread - Sept. 08 | c. Northwards spread - April 09 | d. Animal import - Sept. 08 | e. Animal import - April 09 |
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1. do nothing beyond the minimum requirements | 46.0% | 33.3% | 25.0% | 42.9% | 17.6% |
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2. vaccinate 100% of holdings in a border PZ | 100.0% | 100.0% | 100.0% | 96.7% | 100.0% |
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3. vaccinate 80% of holdings in a PZ to the Highland B/F line | 98.1% | 100.0% | 100.0% | 100.0% | 100.0% |
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4. vaccinate 50% of holdings in a PZ comprising the whole of Scotland | 100.0% | 100.0% | 100.0% | 100.0% | 100.0% |
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5. vaccinate 80% of holdings in a 100km PZ around the first affected holding (only if the incursion occurs above the Highland B/F line) | NA | NA | NA | 95.5% | NA |
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Figure 3.2. Changes in the number of affected holdings over time for different incursion/control scenarios. ( a, b) Incursion via northwards spread in July 2008 with: ( a) minimal control; and ( b) reactive vaccination of all farms in a border protection zone ( PZ). ( c, d) Incursion via animal import in September 2008 with: ( c) minimal control; and ( d) reactive vaccination of 80% of farms in a 100km radius PZ. ( e, f) Incursion via animal import in April 2009 with: ( e) minimal control; and ( f) prophylactic vaccination of 50% of farms in a PZ comprising all of Scotland. Lines in each figure represent the results of individual replicates.
Figure 3.3. Incursion via animal import in April 2009 with either minimal control (left-hand maps) or prophylactic vaccination of 50% of farms in a protection zone comprising all of Scotland (right-hand graphs). The legend indicates the proportion (%) of replicates for which each 5km grid square contained at least one affected farm.
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