By Sarah Long
8 April 2008 [MEDIAGLOBAL]: Innovative use of satellite imaging technology in Thailand and Vietnam has enabled scientists to better understand the factors that contribute to the perpetuation and spread of H5N1, a highly pathogenic strain of bird flu.
Duck population and patterns of rice cultivation were found to be among the most significant factors in H5N1 breakouts in the two countries. This new information will allow governments to better target and combat potential epidemics.
“We now know much better where and when to expect H5N1 flare-ups,” Jan Slingenbergh, senior veterinary officer at the Food and Agriculture Organization (FAO) said in a recent statement. “And this [knowledge] helps to target prevention and control.”
These findings, reported in the publication Proceedings of the National Academy of Sciences of the United States, outlined the innovative methodology experts from the FAO and associated research centers used to discover these surprising correlations.
Satellite images of the countries were used to map a number of factors believed to have a role in H5N1 outbreaks. These included duck and chicken population movement and growth, human population, rice agricultural patterns and local geography. Scientists were then able to identify which of these factors were most often present when bird flu outbreaks occurred.
The study found that ducks, rather than chickens, appeared to be the major conveyors of bird flu in these two countries; where there were swells in duck population, outbreaks of H5N1 were likely to follow.
Duck population, satellite information revealed, tends to follow patterns of rice harvest around the country, as ducks subsist primarily on rice grains left over after the harvest. Therefore duck populations tend to be highest immediately following the harvest.
“Rice cropping intensity turns out [to be] a very viable predictor of a disease in birds,” Slingenbergh told MediaGlobal. “The satellite-derived information about cropping intensity tells us about the behavior of influenza H5N1 virus.”
“It is remarkable because there is as such no direct link between the rice cropping activity and the behavior of a disease. It all works indirectly,” Slingenbergh explained.
Avian influenza primarily affects bird populations, with relatively few cases occurring in humans. However, if left unchecked in birds, there is a greater chance that the virus will mutate to enable transmission not only from birds to humans, but from humans to other humans, with the potential to become a dangerous epidemic. Therefore, the best way to protect humans from bird flu is prevention – controlling avian influenza while it is still a purely avian disease.
With more global movement of both bird and human populations than ever before, the presence of bird flu anywhere is a threat to public health everywhere.
Using the most modern technology to enable more effective control of bird flu in the developing nations of Asia, where avian influenza has in some areas become endemic, is in everyone’s best interest.
Slingenbergh hopes that this study will provide a model to identify the factors important to bird flu perpetuation in other Asian countries. Such detailed knowledge will allow countries to tailor their programs to their own individual needs, making them much more likely to succeed.
The methodology is now being adapted for use in Indonesia and China — two of the countries most affected by the H5N1 epidemic.
Furthermore, the unique satellite imaging methods used in this study could well have implications beyond bird flu. “Links between disease behavior, wetlands, land use, irrigation [and] climate also exist for other diseases,” Slingenbergh told MediaGlobal, expressing the hope that similar methodology could prove useful in combating other dangerous epidemics around the world.