Backyard poultry face HPAI risk when migrating mallards stop to rest

Knowing where, when and for how long mallard ducks – natural carriers of avian influenza – stop and rest as they migrate can help predict the probability that they will spread bird flu to backyard poultry flocks, according to a Cornell University study.

The finding, published in Scientific Reports, takes an important step in explaining the transmission dynamics of bird flu, a strain also known as Highly Pathogenic Avian Influenza (HPAI), and could one day inform people with backyard poultry of the best times to take extra precautions to isolate their birds from wild ones.

The researchers used a computer model to predict infection risk to backyard poultry, resident mallards and overwintering mute swans in Croatia, which serves as a stopover area for both migratory mallards and the swans. While mallards tolerate avian influenza well, it is fatal to mute swans; the dead birds can serve to alert people to the presence of bird flu that is otherwise hard to detect in the wild.

Though Croatia served as a study system in this paper, the results are relevant to other places, including the United States.

Jumping virus

“The virus has jumped independently at different times from wild birds to dairy cows,” said Sebastian Llanos-Soto, a doctoral student in the lab of senior author Renata Ivanek, professor of epidemiology.

“There is an urgent need to improve our ability to predict the introduction of avian influenza at the wildlife-domestic animal interface and our study contributes to this goal,” Llanos-Soto said.

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In the study, the computer model was informed with migratory data, with migratory mute swans arriving in Croatia between September and November to winter and returning to breeding grounds between February and April. Mallards arrive between October and November for a stopover of seven to 28 days before continuing on their migration through the Mediterranean-Black Sea flyway.

The model simulated the transmission of HPAI in an area considered to be of high risk for introduction into poultry farms via waterfowl. The model was validated with real-world bird and farm data from the study area.

The study was funded by the College of Veterinary Medicine; the Cornell Institute for Digital Agriculture; and the U.S. Department of Agriculture National Institute of Food and Agriculture.