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BVD-infection-risk_2004 BVDV-INFECTION-RISK IN THE COURSE OF THE VOLUNTARY BVDV-ERADICATION PROGRAM IN STYRIA/AUSTRIA OBRITZHAUSER W. a,c, FUCHS, K. b, KÖFER, J. c a Veterinary Laboratory, A-8605 Parschlug, Austria b Institute for Applied Statistics and System Analysis, Joanneum Research, A-8010 Graz, Austria c Animal Health Service of the Department of Veterinary Administration, Styrian Provincial Government, A-8010 Graz, Austria

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BVD-infection-risk_2004 Population of bovines in Styria (2003) Bovine herds 17,365 Cows (approx.) 147,000 on average8.5 cows / herd Young stock (approx.) 190,000 Bovines total (approx.) 337,000 on average 19.4 bovines / herd BVDV-infection-risk

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BVD-infection-risk_2004 1998Voluntary BVDV-eradication program 2001Voluntary BVDV-eradication program in breeding herds 2004 Compulsory national BVDV-eradication program in Austria (01-Aug-2004) in all cattle herds (with the exeption of fattening herds) BVDV-infection-risk BVDV-eradication in Styria (Scandinavian eradication scheme)

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BVD-infection-risk_2004 Tests for BVDV (antibodies, BVD-virus) of all animals intended for common pastures (since March 2001) Tests for BVDV (antibodies, BVD-virus) of all animals intended for breeding market places (since 2001) Repeated bulk milk tests for antibodies to BVDV (2001 – 2004: 2 times a year in breeding herds only) Voluntary BVDV-eradication program in breeding herds 2001 - 2004 BVDV-infection-risk

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BVD-infection-risk_2004 Repeated spot tests to identify/monitor presumably non-infected herds (depending on bulk milk test results) Investigations for BVDV in herds identified as possibly infected; removal of the PI-animals Follow-up tests of all calves born during one year after removal of the last PI from the herd Certification of herds which proved to be free of BVDV BVDV-infection-risk Voluntary BVDV-eradication program in breeding herds 2001 - 2004

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BVD-infection-risk_2004 TestSample (matrix) MethodAge at sampling BVD-Ab(bulk) milk Serum Plasma BVDV-Ab Svanovir All samples are tested BVD- Virus detection Whole blood (EDTA), leucocyte fraction IDEXX HerdCheck BVDV Ag/Leuco- cytes > 28 days< 6 months: all animals are tested > 6 months: Ab-negativ animals are tested > 6 months: no BVD-Ag test, if the result of spot test on blood samples (BVD-Ab) is pre-sumably non-infected < 28 daysonly BVD-Ab negative samples are tested for BVD- Ag Serum Plasma RT-PCR> 28 daysdoubtful results; pooled samples Diagnostic strategy BVDV-infection-risk

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BVD-infection-risk_2004 n% Herds in Styria (1) 17,365 Cattle in Styria (2) 336,956 Herds participating in the eradication program (2) 4,41225.4 Cattle in herds covered by the eradication program (2) 147,06943.6 PI animals identified (3) 1,362 PI animals identified in breeding herds (3) 1,034 Herds with PI-animals (1) 850 Breeding herds with PI-animals (1) 60313.7 (1) 30-06-2004 (2) 31-07-2004 (3) 01-01-2001 – 31-07-2004 BVDV-infection-risk Voluntary BVDV-eradication program in breeding herds 2001 – 2004 (3)

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BVD-infection-risk_2004 N herds% Non-infected Low level of antibodies in bulk milk 1,744 Non-infected (spot test young stock) 1,044 Non-infected (spot test young stock) last test more than 6 months ago 324 Non-infected (total)3,11270.6 (Possibly) infected3197.2 Ambiguous3287.4 No tests65314.8 Herds total4,412100.0 BVDV-infection-risk Voluntary BVDV-eradication program in breeding herds status 31-07-2004

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BVD-infection-risk_2004 fattening herds (not covered by the BVDV-eradication program) breeding herds (covered by the BVDV- eradication program) non-breeding herds (not covered by the BVDV- eradication program) cattle markets common pastures purchase & trade exhibitions import BVDV-infection-risk

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BVD-infection-risk_2004 BVD- database ELISA- READER (WinRead) herds..... animals..... Ab/Ag- ELISA results..... bulk milk ELISA results..... result bulk milk- test..... result Ab/Ag tests..... Summ. test results..... report Ab/Ag tests..... report BVD- status..... report PI- animals..... reports process controll.......... AMA- database common pastures markets Breeding Organisations epidem. data Process Controll Sampl. report auctions common pastures..... Sampl. data sheet.......... Sampl. control report..... VETGIS screens BVDV-infection-risk

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BVD-infection-risk_2004 BVDV-infection-risk BVDV-infected herds* - BVDV-eradication program in Styria * herds are grouped as BVDV- infected untill 1 year after iden- tification of the last PI-animal in the herd

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BVD-infection-risk_2004 First identified PI per BVDV-infected breeding herd – month of birth BVDV-infection-risk

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BVD-infection-risk_2004 in the course of a voluntary BVDV-eradication program ? Scandinavian eradication sheme Eradication without vaccination in a cattle-population which is only in part covered by the BVDV-eradication program ? 4,412 breeding herds (25.4 % of all cattle herds in Styria) 147,000 cattle (43.6 % of all bovines in Styria) in a cattle-population in which putting cattle to common pastures and purchase of cattle is widespread ? 35,000 cattle from 4,100 herds put to common pastures per season Up to 26,000 cattle (10,500 female, 15,500 male) are purchased BVDV-infection-risk How does BVDV-infection-risk develop...

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BVD-infection-risk_2004 Exposures: Common pastures Cattle trade (purchase) BVD-control program (overall risk) Risk assessment BVDV-infection-risk Periods of time: Time before the beginning of the BVDV-eradication program (2001) compared to the first 30 months after the implementation of the BVDV-eradication program (2003) For the period from Aug-2002 to Jul-2003 compared to the period from Aug-2003 to Jul-2004

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BVD-infection-risk_2004 03 / 2001 – 06 / 2001: BVD-tests in cattle intended for common pastures and follow-up tests in breeding herds Deadline* for new infections in breeding herds sending cattle to common pastures: 2001-15-12 09 / 2001 – 12 / 2001: bulk milk tests and follow-up tests in all breeding herds Deadline* for new infections in breeding herds not sending cattle to common pastures : 2002-30-06 Risk assessment * Date of birth of the oldest detected PI-animal per herd BVDV-infection-risk

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BVD-infection-risk_2004 RISK RATIO (RR) R elative measure of the difference in risk between the exposed and unexposed population. Def.: The rate of disease among the exposed divided by the rate of the diseased among the unexposed. A relative risk of 2 means that the exposed group has twice the disease risk as the unexposed group. ODDS RATIO (OR) W ay of assessing whether the probability of a certain event is the same for two groups. Def.: Odds of diseased being exposed divided by odds of not diseased being exposed. An odds ratio greater than one implies that the event is more likely in the first group. An odds ratio less than one implies that the event is less likely in the first group. RR = a * (c + d) / c * (a + b) OR = (a / c) / (b / d) Measures of risk 95% CI = 95% confidence-intervall BVDV-infection-risk

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BVD-infection-risk_2004 Compared to the time before the implementation of the eradication program, the risk of BVDV-infections in herds using common pastures, was at least 4 times lower during the first 30 months of the eradication program. RR = 5,22 * OR = 5,77 * RR/OR for breeding herds sharing common pastures with other herds before and after the implementation of the BVDV-eradication program 95% CI: [ 3.83 – 7.11] 95% CI: [ 4.19 – 7.97] * = p < 0,05 * first 30 months BVDV-infection-risk

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BVD-infection-risk_2004 Compared to the time before the beginning of the eradication program, the risk of BVDV-infections in herds with purchased cattle was considered to be at least 8 times lower after the eradication program had been established. RR = 10,32 * OR = 11,45 * RR/OR for breeding herds with purchased cattle before and after the implementation of the BVDV-eradication program 95% CI: [ 7.17 – 14.87] 95% CI: [ 7.89 – 16.62] * = p < 0,05 * first 30 months BVDV-infection-risk

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BVD-infection-risk_2004 In 2001 the overall risk of BVDV-infections in breeding herds in Styria appeared to be 5 - 9 times higher than after the implementation of the BVDV-eradication program. RR = 6.27 * OR = 6.81 * RR/OR for breeding herds in Styria - overall risk before and after the implementation of the BVDV-eradication program 95% CI: [ 4.79 – 8.20] 95% CI: [ 5.16 – 8.97] * = p < 0,05 * first 30 months BVDV-infection-risk

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BVD-infection-risk_2004 Exposure ORRRp LL 95%-CImeanUL 95%-CILL 95%-CImeanUL 95%-CI Herds using common pastures 4.195.777.973.835.227.11< 0,05 Herds with purchased cattle 7.8911.4516.627.1710.3214.87< 0.05 All herds (overall risk) 5.166.818.974.796.278.20< 0,05 Odds-Ratio (OR) and Risk Ratio (RR) for breeding herds before compared to the first 30 months after the implementation of the BVDV-eradication program 95 %-CI = confidence intervallLL = lower limitUL = upper limitp < 0,05 = significant BVDV-infection-risk

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BVD-infection-risk_2004 Exposure ORRRp LL 95%-CImeanUL 95%-CILL 95%-CImeanUL 95%-CI Herds using common pastures 1.051.793.061.041.773.00< 0,05 Herds with purchased cattle 1.151.943.301.141.923.24< 0.05 All herds (overall risk) 1.462.253.461.452.233.42< 0,05 Odds-Ratio (OR) and Risk Ratio (RR) for breeding herds period Aug-2002 to Jul-2003 compared to period Aug-2003 to Jul-2004 95 %-CI = confidence intervallLL = lower limitUL = upper limitp < 0,05 = significant BVDV-infection-risk

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BVD-infection-risk_2004 Period ORRRp LL 95%-CImeanUL 95%-CILL 95%-CImeanUL 95%-CI Before implementation of the BVDV-eradication program Herds using common pastures 1.421.772.211.371.682.06< 0.05 Herds with purchased cattle 1.201.562.021.181.501.90< 0.05 In the course of the BVDV-eradication program (first 30 months) Herds using common pastures 1.743.185.811.733.135.68< 0.05 Herds with purchased cattle 0.641.403.060.641.403.03n.s. Odds-Ratio (OR) and Risk Ratio (RR) for exposed breeding herds compared to not-exposed breeding herds 95 %-CI = confidence intervall LL = lower limit UL = upper limit p < 0,05 = significant n.s. = not significant BVDV-infection-risk

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BVD-infection-risk_2004 Period ORRRp LL 95%-CImeanUL 95%-CILL 95%-CImeanUL 95%-CI Aug-2002 to Jul-2003 Herds using common pastures 0.971.572.540.971.552.50n.s. Herds with purchased cattle 0.801.352.290.801.352.26n.s. Aug-2003 to Jul-2004 Herds using common pastures 1.393.046.661.393.026.57< 0.05 Herds with purchased cattle 0.861.823.830.861.813.80n.s. Odds-Ratio (OR) and Risk Ratio (RR) for exposed breeding herds compared to not-exposed breeding herds 95 %-CI = confidence intervall LL = lower limit UL = upper limit p < 0,05 = significant n.s. = not significant BVDV-infection-risk

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BVD-infection-risk_2004 The BVDV-eradication program in Styria was successful in decreasing the BVDV-infection risk significantly New BVDV-infections could not be totally ruled out under the conditions of the voluntary BVDV-eradication program in Styria New infections could be explained in almost all cases by incom- pliance with the conditions of the BVDV-eradication program A further decrease of the risk of BVDV-infections requires the introduction of a compulsory BVDV-eradication program for all herds BVDV-infection-risk Conclusion:

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