PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
Participatory epidemiology: A tool to
evaluate impacts of FMD among livestock
owners in Cambodia
C. Bellet1, T. Vergne1,2, V. Grosbois1, D. Holl3, F. Roger1,
F. Goutard1
1CIRAD, AGIRs, Montpellier, France
2ENVA-ANSES, USC EpiMAI, Maisons-Alfort, France
3NaVRI, Phnom Penh, Cambodia
@ Goutard
PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
World health
context
Constraints of
developing countries
- To reinforce surveillance of TADs & EIDs
- To define priorities in surveillance :
Where?
When?
Which resources ?
- To use local knowledge in the surveillance
Improving surveillance
while adapting the
capacities to the needs
Tools and methods
to quantify performances
Se, Sp, VPP
Critical points
- To integrate surveillance in the OH concept
REVASIA program : Background

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
REVASIA Program
Development of methods and tools for the evaluation of TADs
and EIDs surveillance systems in SEA
• Influenza
– Avian (SEA, Egypt)
– Swine (Vietnam)
– Human, zoonosis (Cambodia)
• FMD (SEA)
• Bluetongue (France,
Australia)
• Neglected diseases: BTB
(France) …..
Assessment of the
current situation:
• Epidemiology
• Qlttve surveillance
systems evaluation
• Health Geography
• Participatory Epi
Research : quantitative
assessment of
surveillance systems
• Capture-Recapture
• “QRA”: Assessment of
complex Systems
• Sampling & Modelling
• Socio-economics
• Bayesian evaluation
Strategy Applied Diseases

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
• Overall mortality rates (data
from 1999 to 2009) : 0.7% in
cattle; 1.9% in buffalo; 6.4% in
pigs.
• Mean prevalence rates (data
from 2005 to 2009) 2.1% in
cattle; 10.5% in buffalo; 2.2% in
pigs.
• Difficulty to assess the real
prevalence of FMD – under
reporting and under detection
FMD prevalence in Cambodia
2005 - 2009
2009
S. Tum et al. 2011. Policy Implications of Foot and Mouth Disease in Cambodia. ICAHS

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
Objectives
– Assess the relative impact of FMD as perceived by
Cambodian smallholders
– To validate the use of participatory epidemiology in
surveillance
– To perform a two-source
capture-recapture analysis with
the list of cases officially
reported at OIE to estimate
2009’s outbreaks, level of
underreporting

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
Methods: Village selection
• Svay Rieng Province, 6 districts
• 51 Villages (according to C-R protocol) proportional
to district size
5
12
8
5
8
13
VIETNAM
CAMBODIA
• In each districts:
– Meeting DV + VAHWs
– Ranking of villages according to
number of animal purchase for 2009
– Animal movement = proxy of infection

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
Methods: PEPI tools
• Keys actors (Provincial & Districts Vets, Village Chiefs, VAHWs)
Semi Structured
Interviews (SSI)
Diseases Pair-Wise
Ranking
Diseases Impact
Matrix Scoring
Proportional
Piling
Cattle-Buffalo and Pigs
diseases and losses
Four top-ranked
diseases
Scoring of losses by
diseases
Relative Incidences and
FMD mortality (2009)

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
Methods: Serological diagnostic
• Cattle and buffalos from 4 months to 2 years old
Estimated infected villages prevalence:
30%; risk α: 5%
PrioCHECK® FMDV NS Kit (PI: 50%):
Se = 92.6%, Sp = 96.1% (Bronsvoort et
al., 2006)
18 animals/village for detection of
disease
FreeCalc program - hypergeometric
exact probability - 99% cut-off value
(Cameron, 1999), for village level
Prevalence.

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
Bayesian modelling
• Method of estimating the sensitivity and specificity
of diagnostic tests and disease prevalence when
the true disease state is unknown.
• Prior knowledge and
observed data can be
combined

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
Capture Recapture
Source 1 Source 2
Official list of FMD oubreaks
Reported to the national level
112 villages infected in 2009
51 villages selected using targeted sampling
Participatory approach + Positive serology
13 villages infected in 2009
Independance of the sources
Chapman estimate:
a c
b
d

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
Results: FMD impact
• Ranking: HSFMDCSFBloody Diarrhea (Reak Murl)
• 10 categories of disease impact (DIC)
• Impact Matrix Scoring:
Category of impacts that appear to show a moderate to strong agreement between villages.
moderate agreement: W = 0.26–0.38, P 0.05; strong agreement: W 0.38, P 0.01
HS 35 (4.4) FMD 19 (2.4)CSF 17 (2.2) BDS 8
1
2
3
4
Most important DIC for HS
1 Score of Relative Weight for DIC

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
Results: FMD characterisation
• Clinical symptoms:
• Ulcers vesicles in mouth, tongue, gum 88%
• Ulcers vesicles on the feet 69%
• Sialorrhea 49%
• Mean relative incidence and mortality at village:
• Cattle / buffaloes : 18% [min–max: 2–46] and 3% [0–19]
• Pigs: 11% [1–41] and 4% [0–29]
• Threshold to report to DV: what’s an outbreak?
• 22% (12/51) when 5 animals sick (2-3 days)
• 38% (19/51) when 10 to 20
• 38% (19/51)when to 30 to 40
• 2% (1/51)over 50
@ Bellet
@ Vergne

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
Results: FMD prevalence
2009-2010
Svay Rieng
Serology testing PEPI
Animal Prevalence
627 animals
18.34%
(CI95% 15-20.9)
18%
Min-max [2-46]
Village Prevalence*
51 villages
44 %
(CI95% 26-62)
84%
Se 92.6 % 87%
(CI95% 60-90)
Sp 96.1 % 30%
(CI95% 10-56)
*Selection biais overestimating P
Bayesian modelling

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
Results: Capture Recapture
2009
Svay Rieng
Capture
Recapture
Village
incidence
rate
46 %
(CI95% 17-74)
@ Bellet
Number of
villages in
source 1
Number of
villages in
source 2
Overlapping
fraction
Estimated number
of infected villages
[CI 95%]
112 13 4 315 [117-514]
Evaluation of official reporting rate to provincial authorities : 0.05 (CI95% 0.03–0.13).

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
Conclusion
• Participatory Epidemiology
– HS higher impact than FMD
– FMD: disease that can be managed until CP
– Increase farmers trust Report threshold
• Evaluation
– Good Se, poor Sp FP +++, FN ---
– Overestimation of FMD cases: 1) Method 2) Mis-diagnosis
• Capture Recapture
– More accurate estimation of FMD Prevalence
– Method highlighting the low level of disease declaration at
provincial level

PENAPH: First Technical workshop
Chiang Mai, Thailand, 11-13 December, 2012
Acknowledgment
This work is part of the Sea-PREID network
« Participatory Research group for Emerging and
infectious Diseases Management in South East Asia »
Facilitators: Miss Hélène Ou and Mr Eav Chan
SEACFMD: Dr Abila, Dr Bouchot
FAO: Dr Tum
NaVRI / DAHP: Dr San, Dr Holl
CIRAD: Dr Roger, Dr Vergne, Dr Grosbois, Dr Bellet
VERGNE, T., GROSBOIS, V., DURAND, B., GOUTARD, F., BELLET, C., HOLL, D.,
ROGER, F., DUFOUR, B.,(2012). A capture–recapture analysis in a
challenging environment: Assessing the epidemiological situation of foot-
and-mouth disease in Cambodia. Preventive Veterinary Medicine. 105(3):
235-243
BELLET, C., VERGNE, T., GROSBOIS, V., HOLL, D., ROGER, F., GOUTARD, F.,
(2012) Evaluating the efficiency of participatory epidemiology to estimate
the incidence and impacts of foot-and mouth disease among livestock
owners in Cambodia. Acta Tropica. 123: 31-38