Spatial epidemiology of avian influenza in Asia and intensifying poultry production systems
1. M. Gilbert
Université Libre de Bruxelles
Livestock Systems and Environment (LSE) Seminar
ILRI, Nairobi, 23 January 2014
Spatial epidemiology of avian influenza in Asia and intensifying poultry production systems
2. Spatial epidemiology of avian influenza in Asia and intensifying poultry production systems
M. Gilbert
Biological control and spatial ecology,
Université Libre de Bruxelles
http://lubies.ulb.ac.be/Spatepi.html
4. A moving target #1: distribution in Thailand
1 Jan 2004 – 1 Jul 2004
1 Jul 2004 – 1 Jul 2005
1 Jul 2005 – end 2008
5. A moving target #2: distribution in Indonesia
2004 - 2008
2009
2010
2011
6. 2006 A moving target #3: distribution in India & Bangladesh
2007-2011
2012
7. Outbreaks
A moving target #3: distribution in China
Human cases
Positive markets
8. How to deal with those different situations ?
Pattern of spread
•Absence can be suitable
Pattern of surveillance and control
•What is an absence ?
Analysis
•Break down by country / epidemic phase
Comparative analysis
•Gain a general understanding from multiple studies
9. Focus on a limited set of factors
•What animal is infected
•Pattern of excretion (quantity, duration)
•Contacts with other hosts
Hosts
•How host are moved;
•How fomites are moved;
•Surveillance, prevention, control
Anthropogenic
•How and where the virus persists outside the host
•How and where poultry are raised
Environment
10. Time line
0
200
400
600
800
1000
1200
1400
2004
2005
2006
2007
2008
2009
2010
2011
2012
EMPRES-I HPAI H5N1 records (Asia)
THA
IDN
CHN
IND
BGD
VNM
25. BRT model in Thailand Van Boeckel et al. PLOS ONE 7(11): e49528. doi:10.1371/journal.pone.0049528
26. Different duck systems
Delineate areas where HPAI can persist
Free-grazing, local movements e.g. Bangladesh, India, Indonesia, Nigeria
Free-grazing intensive movements e.g. Central plain of Thailand, Vietnam deltas
Farmed e.g. North- eastern Thailand
28. Review paper on HPAI H5N1 risk factors
•Factors have been studied at various scale: farm to country level;
•Factors were very different from one study to another: real difficulty in comparing studies outcomes;
•Overall, some factors showed consistent association with the risk of HPAI H5N1 presence across countries and scales:
•Domestick duck density;
•Anthropogenic (Human pop. density, distance to roads, markets)
•Indicators of water presence
•The effect of chicken density is variable, most likely due to differences in production systems
29. Review of HPAI H5N1 risk factors
•Factors have been overlooked:
•Socio-economic;
•Trade and market networks;
•Wild bird distribution and movement;
32. China: 75% of ducks
•Outbreaks (mainly in chicken farms)
•H5N1 positives from markets Martin et al. (2011) Plos Pathogens 7(3): e1001308
33. BRT model
•Outbreaks
•Chicken and human pop. density;
•More emphasis on the intensive productions areas
•Market surveillance
•Hpop, duck density, and % water.
•Duck/rice ecosystem in the south Martin et al. (2011) Plos Pathogens 7(3): e1001308
39. •Poyang lake: main lake for migratory watefowls
Poyang lake populations
0.5 million wild birds (75 species);
3 millions « farmed » wild birds;
Surrounded by 10 counties with
26 million ducks and geese in farms;
21 million domestic chicken in farms;
6 million people;
43. Intensified poultry production rapidly, duck population that outweights all other coutries
In regions with extensive interface with the wild avifauna
Connectivity between regions is facilitated by long-distance trade between live-bird markets
Relevance to H7N9 ?
China
44. A quick virtual tour in Huzhou
Detailed investigation for all 12 confirmed H7N9 cases in Huzhou, Zhejiang province (http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20481). Linked to markets with: Chickens infection rate of samples = 36 / 129 = 27% Pigeon infection rate of samples = 2 / 6 = 33%
50. H7N9 in China: var space
•Human population
•Duck population
•Chicken population
•% of land occupied by water
•% of land occupied by rice paddy fields
•Accessibilit y(travel time to major cities)
•Live-bird market density
54. Live bird markets
•Important and widespread in China, Vietnam, Bangladesh, Indonesia, Cambodia
•Can allow disease spread and persistence through the meta-population of live-bird markets
•Social Network Analysis combined with mathematical modelling shows potential for targetting markets where intervention would be most beneficial (Fournie et al. 2012, 2013)
•The current missing elements to understand AI (H5N1/H7N9) persistence and spread ?
57. Where are we going ?
•On-going intensification in China, extensive wild bird interface, high LBM density
•India / Bangladesh: intensification, duck population, extensive interface with wild birds, live bird markets
•Is large-scale farming with high biosafety the only way to intensify production safely ?
•Can subsistance and commercial poultry farming co- exist ?
58. Back to Thailand
One of the highest density of domestick ducks;
Extensive irrigated land;
Large commercial sector;
Smallholders & native chickens;
High human population density;
Few or no live-bird markets
59. Conclusion
•Key role of ducks => differ according to production systems
•Intensification of duck production in contact with WB genetic pool of viruses
•Spread to other poultry and human exposure facilitated by LBM networks
•Try not having both
60. Thank you
Acknowledgments: J. Cappelle, L. Hogerwerf, L. Loth, V. Martin, S. Newman, M. Paul, D. Pfeiffer, D. Prosser, T. Robinson, J. Slingenbergh, K. Stevens, W. Thapongtharm, T. Boeckel, R. Wallace, W. Wint, X. Xiao ,