UNITED NATIONS, March 26: Ducks, rice and people — and not chickens — have emerged as the most significant factors in the spread of avian influenza in Thailand and Vietnam, says a new study by the United Nations Food and Agriculture Organisation (FAO).

“Mapping H5N1 highly pathogenic avian influenza risk in Southeast Asia: ducks, rice and people” also finds that these factors are probably behind persistent outbreaks in other countries such as Cambodia and Laos.

The study, which examined a series of outbreak of avian influenza in Thailand and Vietnam between early 2004 and late 2005, was initiated and coordinated by FAO senior veterinary officer Jan Slingenbergh and published in the latest issue of the Proceedings of the National Academy of Sciences of the United States.

Through the use of satellite mapping, researchers looked at a number of factors, including the numbers of ducks, geese and chickens, human population size, rice cultivation and geography, and found a strong link between duck grazing patterns and rice cropping intensity.

In Thailand, for example, the proportion of young ducks in flocks was found to peak in September-October; these rapidly growing young ducks can therefore benefit from

the peak of the rice harvest in November-December.

“These peaks in congregation of ducks indicate periods in which there is an increase in the chances for virus release and exposure, and rice paddies often become a temporary habitat for wild bird species,” the agency said in a news release.

“We now know much better where and when to expect H5N1 flare-ups.”

The paper notes that there is a strong link between duck grazing patterns and rice cropping intensity. Ducks feed mainly on leftover rice grains in harvested paddy fields, so free-ranging ducks in both countries are moved to many different sites in line with rice harvest patterns.