Participatory epidemiology: A tool to evaluate impacts of FMD among livestock owners in Cambodia
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This document summarizes a study that used participatory epidemiology methods to evaluate the impact of foot-and-mouth disease (FMD) among livestock owners in Cambodia. Key findings include: 1) Livestock owners ranked FMD as the second highest disease impact after hemorrhagic septicemia. 2) Village-level surveys estimated the relative incidence of FMD at 18% for cattle/buffaloes and 11% for pigs. 3) A capture-recapture analysis estimated the true number of FMD-infected villages in 2009 was 315, much higher than the 112 officially reported, indicating low levels of disease reporting.
![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](https://image.slidesharecdn.com/penaphbellet-130425034817-phpapp02/85/Participatory-epidemiology-A-tool-to-evaluate-impacts-of-FMD-among-livestock-owners-in-Cambodia-12-320.jpg)
![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](https://image.slidesharecdn.com/penaphbellet-130425034817-phpapp02/85/Participatory-epidemiology-A-tool-to-evaluate-impacts-of-FMD-among-livestock-owners-in-Cambodia-13-320.jpg)
![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).](https://image.slidesharecdn.com/penaphbellet-130425034817-phpapp02/85/Participatory-epidemiology-A-tool-to-evaluate-impacts-of-FMD-among-livestock-owners-in-Cambodia-14-320.jpg)
Participatory epidemiology: A tool to evaluate impacts of FMD among livestock owners in Cambodia
- 1. 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
- 2. 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
- 3. 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
- 4. 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
- 5. 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
- 6. 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
- 7. 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)
- 8. 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.
- 9. 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
- 10. 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
- 11. 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
- 12. 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
- 13. 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
- 14. 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).
- 15. 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
- 16. 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