Bird flu has potential to make fall return

PIERRE — The avian flu that shut down some poultry farms in South Dakota this spring could be a threat again this fall, when temperatures cool and waterfowl make their southern migration back from Canada, the state’s top animal-health official said Tuesday.

South Dakota hasn’t seen a new outbreak of avian flu since May 28, but the virus remains active for 180 to 210 days, including at fields and ponds where wild birds stop and feed, state veterinarian Dustin Oedekoven said.

He told members of the state animal industry board that their May 20 ban against poultry exhibitions, such as at 4-H events and the South Dakota State Fair, should remain in place.

State animal-health officials will give presentations on bio-security to agriculture producers during the Sept. 2-7 state fair.

The South Dakota outbreaks began in late March and eventually spread into a variety of turkey and chicken farms in eight counties.

Oedekoven and his staff imposed control zones to monitor vehicle traffic and worked with firefighters to euthanize infected flocks by using foam sprayed from fire trucks.

The control zones have since been released.

He said poultry barns next to cornfields appear more susceptible according to Minnesota researchers.

Migratory wild birds feed in the fields in the fall, contaminating them with the virus, he said, then farmers prepare the fields for spring planting, stirring the virus into the air.

The virus seems able to survive for roughly 3280 feet, carried on the wind into barns.

An infected poultry barn then becomes “a constant virus factory” with the air-circulation system fanning the virus back into the outside environment, according to Oedekoven.

The virus constantly changes and mutates in the wild bird flocks, and those birds mix on their summer ranges in northern Canada, he said.

The infections seem to stall in South Dakota’s summer temperatures. “We were looking for this type of heat to slow the virus,” Oedekoven said.

The latest variation of the virus doesn’t seem to have infected pheasants and grouse to this point and doesn’t seem to have affected the health of human beings. There isn’t a commercial vaccine available.

Federal monitoring of wild birds for the disease stopped in 2012. “That’s one thing that got cut,” Oedekoven said.

There are many steps that producers can take to potentially reduce risk, but there’s no sure prevention as wild birds return.

“What recommendation do we have for that?” Oedekoven said. “It’s not going to be so simple.”

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