the use of epidemiology to support decision making

Chaidate Inchaisri Department of veterinary Medicine

Faculty of Veterinary Science Chulalongkorn university

E-mail address: Chaidate@hotmail.com

Field epidemiology

• “A primary goal of field epidemiology is to inform, as quickly as possible, the processes of selecting and implementing interventions to lessen or prevent illness or death when such problems arise” (Goodman and Buehler, 2008)

• An emergic diseases

– Require quick response diagnosis and managements

Disease control in endemic areas

• How to reduce and prevent the spread of infection?

• How to reduce disease loss?

• Do we need to eradicate or to live with disease?

• In long term, is it possible to eradicate that disease in some areas?

• If yes, How to do it? – Epidemiological study

• Host, agent, environment and transmission

– Difference locations, farms – Difference strategies

Epidemiological procedure

• Identify problems

• Study designs

• Explore for visualization

• Find risk factors, associations between factors, causes

• Evaluate the effect on production (animal performance)

• Evaluate the effect on economics and social

• Give priority and make decision

Veterinary epidemiology

Multivariable analysis

Tempo-spatial and network

analysis

Economics

Simulation model

The epidemiological techniques

0 (n=38)

2.24 (n=89)

32.96 (n=91)

11.11 (n=117)

13.08 (n=107)

13.79 (n=116)

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2549 2550 2551 2552 2553 2554

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6.11 (n=229)

14.74 (n=217)

16.08 (n=286)

1.18 (n=253)

0.49 (n=204)

10.76 (n=223)

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2549 2550 2551 2552 2553 2554

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1.67 (n=179)

3.1 (n=483) 1.76

(n=452) 0.31 (n=314)

0.3 (n=329)

6.45 (n=341)

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2549 2550 2551 2552 2553 2554

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กาญจนบร

1.38 (n=217)

8.73 (n=206)

0.47 (n=209)

0.35 (n=280)

0.89 (n=224)

7.14 (n=224)

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0.36 (n=548)

2.23 (n=760) 0.98

(n=813) 0.32

(n=913) 0.13

(n=760)

1.81 (n=827)

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2549 2550 2551 2552 2553 2554

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ประจวบครขนธ

1.85 (n=103)

11.68 (n=77)

1.28 (n=156)

6.28 (n=175)

6.04 (n=149)

6.53 (n=152)

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2549 2550 2551 2552 2553 2554

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นครปฐม (Panumas et al., 2554)

n=7-9 n=52-87

n=16-19 n=28-39

n=13-17

n =40-46

n=2-8

n=7-12 n=25-32

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A B C D E F G H I J K L M N O P

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Farm (n=2-112 per farm)

เมษายน สงหาคม ธนวาคม

(Panumas et al., 2554)

Percent of serum positive per flock

DLD strategy

• Test and slaughter

– A serum positive goat by a serial test of ELISA and complement fixation test (CFT) is eradicated.

– For a positive farm, all goats are retested until no more positive results in the herd (a negative farm at level B).

– After 6 months, a goat farm is declared to be free from brucellosis at the level A when all goats in flocks level B are negative for the sequence tests.

The structure of model for one time step

Flock size • Population structure

• Prevalence

Test • Sensitivity

• Specificity

Culling • Positive serum test

• Old goat, death

• Sales

Kidding

Negative serum test

Service per

pregnancy

Abortion

Kid death

Sales • Closed flock • Constant flock size • Contact transmission rate???

Monte Carlo Stochastic-dynamics Approach

Input data used for the simulation model

Parameters Default

Flock size Lognorm(27,32)

Prevalence RiskUniform(0.01,0.5)

Sensitivity

ELISA RiskUniform(0.87,0.89)

CFT RiskUniform(0.79,0.82)

Specificity

ELISA RiskUniform(0.84,0.99)

CFT RiskUniform(0.87,1)

Contact number per month RiskPoisson(10, RiskTruncate(1,30))

Transmission per contact RiskUniform(0.0005,0.001)

Transmission per service RiskUniform(0.4,1)

Ratio female per male RiskTriang(1,1,38.2)

Number services per pregnancy RiskNormal(1.7, 0.9), RiskTruncate(1,3)

Litter size RiskNormal(1.2,0.4), RiskTruncate(1,4)

Kidding per year RiskNormal(1.34,10), RiskTruncate(1,2)

Abortion rate RiskNormal(0.03,0.03), RiskTruncate(0,0.5)

Kid death rate RiskNormal(0.13,0.03), RiskTruncate(0.07,0.2)

Adult death rate RiskUniform(0.05,0.15) Program interval 1-12 months

No strategy to control disease

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Months

Stochastic default values (10,000 flocks)

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Months

Stochastic default values (10,000 flocks)

Percent of successive flocks in eradication program with uncertain inputs

99 98 95

99 98 95

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1 3 6

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Eradication Program Interval (months)

Perfect specificity Average specificity Poor specificity

Increase transmission per contact

Eradication program interval = 3 months

Within 1 year

Network between flocks with the size of node represents the value of degree centrality with positive flock (red circle) and negative flock (blue circle). The box node represents the flocks without knowing disease status.

Conclusions • The important of animal movements on spreading of

disease and the specificity of diagnostic test in eradication program

• Add other strategies – Add other methods or technologies to control animal

movement – Simultaneous test and slaughter program with animal

movement control – Establish the goat farmer community to reduce

uncontrollable movements between provinces – Quarantine farms – Improve the specificity of diagnostic test – When the prevalence at flock level is very low and the

specificity of diagnostic test is poor, consider culling positive flocks.

Further studies

• Do more research in other areas

• Production structure, production chain, value chain

• Evaluate the success of other strategis

• Evaluate the economical benefit of other programs

GISTA (Geo-Informatics and Space Technology Development Agency)

ส ำนกงำนพฒนำเทคโนโลยอวกำศและภมสำรสนเทศ (องคกำรมหำชน)

-10

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เปอรเซนตของพนททไดรบผลกระทบจากปญหาอทกภย

อ.ชมแสง

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82%

51%

30%

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53% 78%

69% 49%

73%

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Representation of location and size of significant clustered areas for poultry farming loss per square kilometer. The degree of loss is indicated by the intensity of color (high intensity 0 high color)

Representation of location and size of significant clustered areas for swine farming loss per square kilometer. The degree of loss is indicated by the intensity of color (high intensity 0 high color)

Conclusions

• Cluster mapping reveals the area with high risk in farming loss due to the flooding

• This helps planners to assess spatial risk factors, and to ascertain what would be the most suitable types of livestock farming and which period should be avoided for the livestock farming

Vet

Society

Farm DLD

University

ปญหำ???

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ศกษำ วจยภำคสนำม

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Thank you