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Chaidate Inchaisri Department of veterinary Medicine
Faculty of Veterinary Science Chulalongkorn university
E-mail address: [email protected]
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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
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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
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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
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Veterinary epidemiology
Multivariable analysis
Tempo-spatial and network
analysis
Economics
Simulation model
The epidemiological techniques
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0 (n=38)
2.24 (n=89)
32.96 (n=91)
11.11 (n=117)
13.08 (n=107)
13.79 (n=116)
048
12162024283236
2549 2550 2551 2552 2553 2554
Pe
rce
nt
of
po
siti
ve f
arm
s
สพรรณบร
6.11 (n=229)
14.74 (n=217)
16.08 (n=286)
1.18 (n=253)
0.49 (n=204)
10.76 (n=223)
0
2
4
6
8
10
12
14
16
18
2549 2550 2551 2552 2553 2554
Pe
rce
nt
of
po
siti
ve f
arm
s
ราชบร
1.67 (n=179)
3.1 (n=483) 1.76
(n=452) 0.31 (n=314)
0.3 (n=329)
6.45 (n=341)
02468
1012141618
2549 2550 2551 2552 2553 2554
Pe
rce
nt
of
po
siti
ve f
arm
s
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)
02468
1012141618
2549 2550 2551 2552 2553 2554
Pe
rce
nt
of
po
siti
ve f
arm
s เพชรบร
0.36 (n=548)
2.23 (n=760) 0.98
(n=813) 0.32
(n=913) 0.13
(n=760)
1.81 (n=827)
02468
1012141618
2549 2550 2551 2552 2553 2554
Pe
rce
nt
of
po
siti
ve f
arm
s
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)
02468
1012141618
2549 2550 2551 2552 2553 2554
Pe
rce
nt
of
po
siti
ve f
arm
s
นครปฐม (Panumas et al., 2554)
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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
0
5
10
15
20
25
30
A B C D E F G H I J K L M N O P
Pe
rce
nt
of
po
siti
ve g
oat
s
Farm (n=2-112 per farm)
เมษายน สงหาคม ธนวาคม
(Panumas et al., 2554)
Percent of serum positive per flock
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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.
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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
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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
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No strategy to control disease
0
10
20
30
40
50
60
0 12 24 36 48 60 72 84 96 108 120 132 144 156 168 180 192 204 216 228 240
Pe
rce
nt
of
10
0%
po
siti
ve f
lock
s
Months
Stochastic default values (10,000 flocks)
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0
10
20
30
40
50
60
70
0 12 24 36 48 60 72 84 96 108 120 132 144 156 168 180 192 204 216 228 240
Pe
rce
nt
of
succ
ess
ive
flo
cks
in
era
dic
atio
n p
rogr
am
Months
Stochastic default values (10,000 flocks)
Percent of successive flocks in eradication program with uncertain inputs
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99 98 95
99 98 95
0
10
20
30
40
50
60
70
80
90
100
1 3 6
Pe
rce
nt
of
succ
ess
ive
flo
cks
in e
rad
iati
on
pro
gram
w
ith
in o
ne
ye
ar
Eradication Program Interval (months)
Perfect specificity Average specificity Poor specificity
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Increase transmission per contact
Eradication program interval = 3 months
Within 1 year
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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.
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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.
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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
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GISTA (Geo-Informatics and Space Technology Development Agency)
ส ำนกงำนพฒนำเทคโนโลยอวกำศและภมสำรสนเทศ (องคกำรมหำชน)
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-10
0
10
20
30
40
50
60
70
80
90
เปอรเซนตของพนททไดรบผลกระทบจากปญหาอทกภย
อ.ชมแสง
อ.เกาเลยว
อ.ทาตะโก
อ.โกรกพระ
อ.เมองนครสวรรค
อ.บรรพตพสย
อ.พยหะคร
อ.ตาคล
อ.หนองบว
อ.ลาดยาว
อ.แมวงก
อ.ไพศาล
กงอ.แมเปน
กงอ.ชมตาบง
อ.ตากฟา
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82%
51%
30%
38%
53% 78%
69% 49%
73%
71%
65%
40%
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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)
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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)
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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
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Vet
Society
Farm DLD
University
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ปญหำ???
วำงแผน ออกแบบกำรศกษำและกำรวเครำะหปญหำ
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รวมมอ รวมใจ
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บรกำรสงคม
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เรยนรชมชน
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ศกษำ วจยภำคสนำม
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รวบรวมขอมล
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วเครำะหขอมล น ำเสนอรปแบบกำรแกปญหำ
ถำยทอดควำมรสชมชน
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Thank you