EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

Thomas Selhorst & Thomas MüllerFLI Friedrich-Löffler-Institut :: Institute for Epidemiology

Wusterhausen/Germany

Scenario-analysis evaluating emergency strategies after rabies

re-introduction

Hans-Hermann Thulke & Dirk Eisinger Helmholtz Centre for Environmental Research UFZ :: Dept. of Ecological Modelling

Leipzig/Germany

Conceptual frame – Alternative Ring – Alternative Dough – Conclusion

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

ScopeScope: Rabies-free region + naïve population

X

Large scale countrywide vaccination successful in past

here economically useless

StrategyStrategy: Limited control area

Conceptual frame – Alternative Ring – Alternative Dough – Conclusion

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

TargetTarget: Eradication + Avoiding breakout from control area

Conceptual frame – Alternative Ring – Alternative Dough – Conclusion

X

Compact circle with 20 baits per km2

Vaccinated area

Unvaccinated area

Rabiesdetection

XX

X

X

X

X

X

X

X

XX

XX

X

StrategyStrategy: Limited control area

Increase control area…

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

Alternative: Alternative: RingRing(Vaccinated area constant + number of baits equal + distance differs)

X

XX

XX

XX

XXX

X

X

X

X

X

COMBAT CONTAIN

CIRCLE RING

XXX

X

X

X

X

X

XX

XX

XX

X

3Conceptual frame – Alternative Ring – Alternative Dough – Conclusion

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

CIRCLE

RING

Time [campaigns]

Simulation resultsSimulation results: Circle vs. Ring ?Conceptual frame – Alternative Ring – Alternative Dough – Conclusion

(10.000 repetitions)R

isk

of B

reak

out

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

Strategy

Risk of breakout higherRing designRing design:

Public Health

0%

20%

40%

60%

80%

100%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Time [# baitings]

Era

dic

ati

on

R - tim e lag 5

R - tim e lag 3

R - tim e lag 1

C - tim e lag 1

0

100

200

300

400

500

600

700

800

900

1000

1 2 3 4 5 6 7 8

Time [# baitings]

Ca

se

s o

f ra

bie

s [

#]

C - time lag 1

R - time lag 5

R - time lag 3

R - time lag 1

Economy More cases of rabies(inner part epidemic starts)

Prolongation of measure(inner part vaccinated later)

Conceptual frame – Alternative Ring – Alternative Dough – Conclusion

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

Conceptual frame – Alternative Ring – Alternative Dough – Conclusion

Eisinger et al. (2005) BMC Inf Dis 5:10Emergency vaccination of rabies under limited resources – combating or containing?

Compact control area Compact control area

around detection around detection

is mandatory!is mandatory!

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

COMBAT COVER

DOUGH

X

XX

XXXX

XXX

X

X

X

X

X XXX

X

X

X

X

X

XX

XX

XX

X

CIRCLE

XXX

X

X

X

X

X

XX

XXXX

X

Focused COMBAT

20 baits per km2 10 baits per km2 40 baits per km2

Alternative: Alternative: Bait density(Immediate combat + Number of baits equal + vaccinated area differs)

Conceptual frame – Alternative Ring – Alternative Dough – Conclusion

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

0

2

4

6

8

10

12

14

16

18

0 10 20 30 40

Baits per km2

Fa

ilure

rate

[%

]

Simulation resultsSimulation results: Area vs. density

__+

?

Dough thinner … Dough thicker

Conceptual frame – Alternative Ring – Alternative Dough – Conclusion

(10.000 repetitions)

Ris

k o

f B

reak

ou

t [%

]

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

0

2

4

6

8

10

12

0 5 10 15 20

Failurerate

Tim

e t

ill 8

0%

su

cc

es

sra

te

[ca

mp

aig

ns

]

5

40

1020

30

7

Dough design by: Dough design by: Strategy slightly thinner advantageous

Public HealthEconomy

The thicker the quicker is eradication

The thicker the fewer rabies cases

0

500

1000

1500

2000

2500

3000

0 5 10 15 20

Failurerate

Ca

se

s o

f ra

bie

s

5

40

1020 30

7

Conceptual frame – Alternative Ring – Alternative Dough – Conclusion

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

ConclusionConclusion

Model-based pre-testing helpful

• Development and evaluation of alternatives

Ring not applicable

• Immediate combat of the outbreak is mandatory

Lower bait density and larger area beneficial

• Trading-off between success and control costs or rabies occurrence

Need for further research!

• Mixed application according to situation

X

x

?

Conceptual frame – Alternative Ring – Alternative Dough – Conclusion

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

Thank youThank you

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

Scenario deduction – Model description – Scenario evaluation – Conclusion & outlook

Model DescriptionModel Description

Evaluation of relative performance of alternative scenarios

Simulation experiment

5

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

Scenario deduction – Model description – Scenario evaluation – Conclusion & outlook

•Fox families in grid cellsSpatial organization

•Reproduction in spring

•Dispersal in autumn

Seasonality

•Individual foxes

(Position & age, sex & disease state)

Population

Model realisation

Simulation model – Rule basedSimulation model – Rule based

suscept. infected infectious empty

i.e. Sayers et al. 1985

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

Scenario deduction – Model description – Scenario evaluation – Conclusion & outlook

Individuals:

Mortality

Reproduction

Bait uptake

Subadults:

Dispersal

Model rules :: BiologyModel rules :: Biology

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

Scenario deduction – Model description – Scenario evaluation – Conclusion & outlook

Neighborhood contacts

Model rules :: Rabies transmissionModel rules :: Rabies transmission

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

Scenario deduction – Model description – Scenario evaluation – Conclusion & outlook

Neighborhood contacts

Mating activity

Model rules :: Rabies transmissionModel rules :: Rabies transmission

Dispersal

EcoEpi – Dept. Ecological Modelling Institute for Epidemiology

Scenario deduction – Model description – Scenario evaluation – Conclusion & outlook

Model rules :: Bait distributionModel rules :: Bait distribution

• 1 - 40 baits/km2 (Spring & Atumn campaigns)

• Spatial assignment to fox families

• Bait competition

• Individual bait uptake