1 country wide eradication

8/3/2019 1 Country Wide Eradication

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BVDV Summer Symposium, 7-8 March 2005, Wellington, New Zealand

Ann LindbergSwedish Dairy Association

Countrywide eradication ofBVDV – how can it be done?



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Outline

Background

Systematic control in Europe

The Swedish BVDV scheme

– Strategy in non-infected herds

– Strategy in infected herds – Biosecurity

– Future challenges

Cost-benefit of control

Predictors for positive progress

General model for BVDV control

Summary



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Background



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Strategies for BVDV control –

”the old differentiation” Immunization(vaccination)

Avoiding exposure(zoo-sanitary approach)



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Non-systematic control approaches

vs

Systematic control approaches



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Systematic control

Goal-oriented, systematic reduction inthe incidence and prevalence of BVDV

infection Implies that progress is being

monitored

Scale – sectoral/regional/national Typically based on the ”avoiding

exposure” approach



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Non-systematic control

Measures implemented on aherd-to-herd decision basis

Typically immunisation strategies

using live or killed vaccines

and/or removal of PI animals inselected cohorts withoutsystematic follow-up



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Systematiccontrol in Europe



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Density of bovines



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Prevalenceof herds with

(any)

antibodies inbulk milk

Initialscreenings

1%

77%37%

95%



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Prevalence ofherds withantibody levels

in bulk milkindicative of

recent/ongoingBVDV infection

1993

<1%

40%7%

40%



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Scandinavian schemes

Schemes on BVDVlaunched in ’93-’94.

Goal =>eradication

Vaccines havenot been and

are notavailable



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General outline of the

schemes Use herd level tests (test strategies) for

screening of herds with unknown status and

for monitoring of free herds Similar general strategy

– Establish probable herd status

– Monitor non-infected herds (antibodies)

– Clear infected herds from the infection

– Biosecurity framework controlling contacts / movements of animals between herds



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Prevalence of herds underinvestigation 1993-2005

0

2

4

6

810

12

14

16

18

1 9 9 3

1 9 9 4

1 9 9 5

1 9 9 6

1 9 9 7

1 9 9 8

1 9 9 9

2 0 0 0

2 0 0 1

2 0 0 2

2 0 0 3

2 0 0 4

2 0 0 5

Year

I n f e c t e d h e

r d s ( % )

SE

DKNO

FI

0.01%

0.77%

0.01%

0.26%



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The SwedishBVDV scheme



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Why eradication?

TB eradicated during the 60s

Long term control of salmonella in the

farm animal sector National eradication scheme on

enzootic bovine leukosis 1990-2000

Low prevalent IBR eradicated during1995-1998.



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Sufficientresources

Pieces that fell in place..

Gooddiagnostics

Financialsolution

Motivation

Goodunderstanding of the

epidemiology



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Organisation Launched in September 1993.

Coordinated by Field work is organised mainly through 8

regional livestock cooperatives

Financed by farmers’ fees and by subsidies fromthe Board of Agriculture

Affiliation – Voluntary: 1993-1997 60% (D-93%; B-27%)

– Industry demand: 1997 (dairy), 1999 (beef)88% (D-100%; B-77%)

– Compulsory: 1 June 2002 (by law)

100%



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Separation between non-infected- and infected herds

using herd level diagnostics

BULKMILK

BULKMILK



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Strategy in non-infected herds



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Screening/monitoring methods

BULKMILK

BULKMILK

5-10

5-10

1.

2.

3.

(7) 12 months



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Certification

BULKMILK

7(12) months



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No individual testing ofanimals in connection with..

..livestock trade

..common pastures

..exhibitions

..i.e. contact with animalsfrom other herds

Perishable goods…

BVDV-

free

Approved sample notolder than 3 months



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Strategy ininfected herds



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Infected herds

Systematic removal of

PI animals

Next presentation!



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Biosecurity



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Biosecurity?



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Re-routing livestock trade

Demand for BVDV free cattle

Access to information on BVDV

status (all involved) Efficient diagnostic system (time

from sampling to status is availableminimised)

Rules and regulations



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Other biosecurity measures

Direct contacts of all kind managed in the samemanner (based on a recent test)

Follow-up testing after potentially risky exposures Direct contacts with sheep/goats dealt with in a

similar way

Transportation staff should not enter cattleaccommodations

Visitors should be provided with clothes/boots to

borrow Double fencing towards adjacent farms

Follow-up testing after ET (imported embryos)



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Future

challenges



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Prevalence of herds with highlevels of antibodies in bulk milk

1993-2004

0

5

10

15

20

25

30

35

40

45

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

%



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Future challenges

Continued import control – (livestock),embryos, semen

BVDV on the OIE agenda

Conclude the scheme!

Intensify work with herdclearances

Use available legislationto handle non-compliers

Regionalisation?

Molecularepidemiology fortracing sources of newinfections

Alternative ways tomonitor beef herds



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Cost-benefit of control



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Cost-benefit NorwegianBVDV programme (1993-2003)

Benefit estimated as expectedlosses – (avoided losses + cost

for control)

Norwegian conditions

Ref: Paul S. Valle, Norwegian School of Veterinary Sciences



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Health and production losses

Effects of BVDV infection on:

Extra days open

Milk production

Culling

Animals lost/died

Treatments


C b fi N i



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Estimated losses without control: 6.9million NZD/year

Cost-efficient already year 2

Benefit ~37.1 million NZD

(discounted value) over whole period

75% of all costs carried by the industry



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-1000

0

1000

2000

3000

4000

5000

6000

7000

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

N

e t c a s h f l o w ( N Z D )




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Predictors for progress



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..intervene ininfected herds


..prevent new

infections

..rapidly

detect new casesof infection

..getacceptance of /

compliance withthe scheme

Ability to..



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Ability to prevent new infections

Efficiency in means to protect free herds – change contact pattern – reduce risk associated with necessary

contacts

Efficiency in means to control infectedherds –

control movements from them – reduce the risk associated with being incontact with them.



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Ability to rapidly detect new

cases of infection Efficiency of diagnostic procedures

– test performance

– test frequency

Efficiency in tracing sources of newinfections

Efficiency in the follow-up of herds that

have not re-confirmed their (free) status Access to subsidies on costs of

monitoring



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Ability to intervene in infected herds

Efficiency of procedures aimed at clearingherds from the virus (diagnostics, logistics).

Strength in incentive to clear infected herds

– voluntary vs compulsory – strength of sanctions

Access to subsidies on costs for elimination of virus from infected herds

Access to compensation for slaughter of PI animals



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Ability to get acceptance of /compliance with the scheme

Ability to communicate expected benefits ofcontrol

Extent of farmer involvement and awareness

Degree of involvement by farmers’ organizations(incl. industry support for sanctions)

Strength in support from authorities (legislation - juridical support for sanctions, subsidies)

Impact of market effects Presence of alternative financial solutions (e.g.

insurance)



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time

Herd size and density

time

Initial prevalence



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time

”Cumulative power”



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The rate of progress of currentsystematic control schemes has notbeen a function of initial prevalence,herd density, herd size etc

It has been dependent on to whatextent they have been able to

develop these ”abilities”!



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General model for BVDV control



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BIOSECURITY



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BIOSECURITY

VIRUS ELIMINATION



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BIOSECURITY

MONITORING

VIRUS ELIMINATION



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BIOSECURITY

IMMUNIZATION

VIRUS ELIMINATION

MONITORING

Advantages with zoosanitary



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Advantages with zoosanitaryapproach

Easier to communicate importance ofbiosecurity

Does not convey a false sense of security

Risk of reinfection is rapidly reduced assoon as trade control is initiated

Easy to interpret diagnostics, possible to

use cheap screening methods

Future investments in monitoring are verylimited



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If systematic reduction of BVDVprevalence is the goal:

Build the pyramid from thebottom…



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Summary



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Summary

The Nordic countries are facingeradication of BVDV, with reductions inprevalence from 40 to <1% in 11 yearstime.



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Vaccines have not been used to protectsusceptible herds

A strong and instantaneous reduction inrisk of reinfection has been gained bylearning farmers to ask for BVDV freecattle..

Summary



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Summary

The strategies chosen have been basedon the preconditions in each country

Progress more related to organisationand ability to take measures, than toinitial prevalence and herd size/density



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Summary

A general model for systematic BVDV controlhas got three necessary steps:

Biosecurity, Virus elimination and Monitoring

Immunization is

– optional – adds a level of complexity

– ”advanced users only”



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Thank you!

1 country wide eradication

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