Tracking Avian Flu With Satellite Observation

Xiao and colleagues were recently awarded $1.55 million for a four-year project funded by the U.S. National Institutes for Health (NIH) as part of the Ecology of Infectious Diseases (EID) Program jointly sponsored with the U.S. National Science Foundation. The EID program supports research projects that develop quantitative analysis and modeling capacity for better understanding the relationship between man-made environmental change and transmission of infectious agents. Certain agricultural and livestock production practices are known to play a critical role in the spread of the Highly Pathogenic Avian Influenza or HPAI.

Xiao, of the UNH Institute for the Study of Earth, Oceans, and Space (EOS) Complex Systems Research Center (CSRC), is the principal investigator for a team that includes international co-investigators Jan Slingenbergh of the United Nations Food and Agriculture Organization in Rome, Italy, Marius Gilbert of the Université Libre de Bruxelles, Brussels, Belgium, and Fumin Lei and Zhongwei Guo of the Institute of Zoology, Chinese Academy of Sciences in Beijing, China. EOS scientist Rob Braswell is also a co-investigator. [1]

The ecology of the avian influenza involves a complex web of factors, including environmental settings, agricultural practices of rice production and harvesting, poultry production involving huge populations of free-grazing ducks, and the migratory behavior of wild bird populations. Depending on how all of these risk factors intermingle over time, the virus can be spread through the environment by infected wild birds or domestic poultry.

The UNH project will use environmental remote sensing data from Earth observing satellites in combination with research in epidemiology, ornithology, and agriculture to provide a better picture of how HPAI survives and gets transmitted among poultry and wild birds. This powerful information will serve to adjust the strategies to reduce the spread of diseases and also to prevent its introduction into areas at risk.

Compared to this time last year, outbreaks of the virus have been low. The exact reasons for this are unknown. However, the research team believes restrictions on the movement of large, free-grazing duck populations could be an important factor. For example, Thailand made great strides in limiting the movement of these duck populations over the past year.

But because their research is based mainly on the links between avian flu, ducks, rice paddy agriculture, and wetland areas in Thailand, the researchers caution that what is true for one region may not apply precisely to others. However, it is believed that similar scenarios exist for other countries in eastern and southeastern Asia where avian flu still occurs because these countries all have significant duck populations and rice agriculture, and wetlands over deltas and plains.

While the trade and traffic of chicken in particular may cause rapid and intercontinental-scale spread of avian flu, domestic ducks grazing in the open fields are believed to act as the "maintenance" host – supporting continuous viral circulation but showing little sign of diseases.

The important role of free-grazing ducks as a source of avian flu infection, including for chicken, was first detailed by Marius Gilbert [2], a spatial ecologist at the Free University of Brussels, working with FAO and Thai investigators in the central plains of Thailand. Gilbert and colleagues discovered that climate and local hydrology dictate the local rice crop calendar, while the availability of post-harvest rice paddy grain, which serves as feed for the ducks, shapes duck husbandry practices.

To fully understand the complex risk pattern, in space and time, of HPAI survival and transmission, a diverse team is required: local experts in rice and duck production systems, epidemiologists, ecologists, agriculturalists, ornithologists (wild birds), spatial modelers, virologists, and remote sensing experts. Together, the team hopes to unravel the puzzle and generate a composite picture of how avian flu, wild birds, poultry, land use, rice agriculture, wetlands and climate are interrelated.

Of the current project, which builds upon related remote sensing work he has done under FAO and National Aeronautic and Space Administration (NASA) funded projects, Xiao adds, "The strength of our group, and of this proposal, is that over the last few years we’ve been able to pull a lot of information out of satellite observations that can help unravel the complex risk factors involved in avian flu ecology."

For example, using imagery of varying resolution from different types of satellites, the team can map and track the spatial-temporal dynamics of crop cultivations (when planted, harvested, etc.) and wetlands. Used in conjunction with other geospatial data of environment, bird migration, and poultry production, dynamic maps of "hot spots" and "hot times" for viral transmission can be developed in near-real-time mode and will aid the public, researchers, business, and decision-makers in preparing for a potential pandemic crisis.

Says Xiao, "It will be interesting for scientists to compare the current situation with last year’s outbreaks in light of the changes in poultry management, agriculture practices, and wild bird migration." And satellite imagery will provide critical information for this comparison. Xiao and colleagues will use the Moderate-resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite for continuous observation at moderate spatial resolution. The four-year project represents a significant enrichment for EOS and CSRC in terms of their traditional areas of focus.

"The Institute as a whole and the center in particular have focused more on remote sensing in the areas of the carbon cycle, the water cycle, biogeochemical cycles and climate change, and this is really the first time we’ve gotten into human and animal health," Xiao says.

Of this new direction , EOS director Berrien Moore says, "We are very proud of Xiangming Xiao and his colleagues. Exploiting new multidisciplinary approaches to complex problems is at the heart of research at EOS. Their work will not only contribute to successful strategies for mitigating a serious health threat, it will also introduce our students to new ways of attacking important and difficult challenges."

[1] Gilbert, Marius et al. Free-grazing Ducks and Highly Pathogenic Avian Influenza, Thailand. Emerging Infectious Diseases Vol. 12, No. 2. February 2006.

[2] Gilbert, Marius et al. Avian influenza, domestic ducks and rice agriculture in Thailand. Agriculture. Ecosystems and Environment. 2006. doi:10.1016/j.agee.2006.09.001

[3] Gilbert, Marius et al. Anatidae Migration in the Western Palearctic and Spread of Highly Pathogenic Avian Influenza H5N1 Virus. Emerging Infectious Diseases. Vol. 12, No. 11. November 2006.