BVD-infection-risk_2004 BVDV-INFECTION-RISK IN THE COURSE OF THE VOLUNTARY BVDV-ERADICATION PROGRAM...

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, Austriab Institute for Applied Statistics and System Analysis,

Joanneum Research, A-8010 Graz, Austriac Animal Health Service of the Department of Veterinary Administration,

Styrian Provincial Government, A-8010 Graz, Austria


Population of bovines in Styria (2003)

Bovine herds 17,365

Cows (approx.) 147,000

on average 8.5 cows / herd

Young stock (approx.) 190,000

Bovines total (approx.) 337,000

on average 19.4 bovines / herd

BVDV-infection-risk


1998 Voluntary BVDV-eradication program

2001 Voluntary BVDV-eradication program inbreeding herds

2004 Compulsory national BVDV-eradicationprogram 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)


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


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


n %

Herds in Styria(1) 17,365

Cattle in Styria(2) 336,956

Herds participating in the eradication program(2) 4,412 25.4

Cattle in herds covered by the eradication program(2) 147,069 43.6

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) 603 13.7

(1) 30-06-2004 (2) 31-07-2004 (3) 01-01-2001 – 31-07-2004

BVDV-infection-riskVoluntary BVDV-eradication program in

breeding herds 2001 – 2004(3)


fattening herds(not covered by the BVDV-eradication

program)

breeding herds

(covered by the BVDV-

eradication

program)

non-breeding herds

(not coveredby the BVDV-

eradicationprogram)

cattle markets

common pastures

purchase & trade

exhibitions

import

import

BVDV-infection-risk


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


BVDV-infected herds

962.2 %

1082.5 %

1373.2 %

2656.3 %

3127.3 %

0

50

100

150

200

250

300

350

I/2002 II/2002 I/2003 II/2003 I/2004

BVDV-infectedherds

BVDV-infection-riskBVDV-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


0

5

10

15

20

25

30

Jän.

96

Jul.9

6

Jän.

97

Jul.9

7

Jän.

98

Jul.9

8

Jän.

99

Jul.9

9

Jän.

00

Jul.0

0

Jän.

01

Jul.0

1

Jän.

02

Jul.0

2

Jän.

03

Jul.0

3

Jän.

04

Jul.0

4

Start of the BVDV-eradication program

First identified PI per BVDV-infected breeding herd – month of birth

BVDV-infection-risk


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 ...


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


RISK RATIO (RR) Relative 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) Way 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.

diseasednot

diseasedtotal

yes a b a+b

no c d c+d

total a+c b+d a+b+c+d=N

disease status

exposure

RR = a * (c + d) / c * (a + b)

OR = (a / c) / (b / d)

Measures of risk

95% CI = 95% confidence-intervall

BVDV-infection-risk


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

infected not infected

before 376 3647 4023

in course* 60 3963 4023

436 7610

BVD-statusBVDV- eradication

* first 30 months

BVDV-infection-risk


Exposure OR RR p

LL 95%-CI mean UL 95%-CI LL 95%-CI mean UL 95%-CI

Herds using common pastures 4.19 5.77 7.97 3.83 5.22 7.11 < 0,05

Herds with purchased cattle 7.89 11.45 16.62 7.17 10.32 14.87 < 0.05

All herds (overall risk) 5.16 6.81 8.97 4.79 6.27 8.20 < 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 intervall LL = lower limit UL = upper limit p < 0,05 = significant

BVDV-infection-risk


Exposure OR RR p


Herds using common pastures 1.05 1.79 3.06 1.04 1.77 3.00 < 0,05

Herds with purchased cattle 1.15 1.94 3.30 1.14 1.92 3.24 < 0.05

All herds (overall risk) 1.46 2.25 3.46 1.45 2.23 3.42 < 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 intervall LL = lower limit UL = upper limit p < 0,05 = significant

BVDV-infection-risk


Period OR RR p


Aug-2002 to Jul-2003

Herds using common pastures 0.97 1.57 2.54 0.97 1.55 2.50 n.s.

Herds with purchased cattle 0.80 1.35 2.29 0.80 1.35 2.26 n.s.

Aug-2003 to Jul-2004

Herds using common pastures 1.39 3.04 6.66 1.39 3.02 6.57 < 0.05

Herds with purchased cattle 0.86 1.82 3.83 0.86 1.81 3.80 n.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


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:

BVD-infection-risk_2004 BVDV-INFECTION-RISK IN THE COURSE OF THE VOLUNTARY BVDV-ERADICATION PROGRAM...

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