Bird flu infects another Sioux County dairy farm

The ISU Veterinary Diagnostic Laboratory tests samples from animals for viruses such as avian influenza. (Photo courtesy of Iowa State University Veterinary Diagnostic Laboratory)

Avian flu has infected cattle of a third dairy farm in northwest Iowa, according to the state Department of Agriculture and Land Stewardship.

All three of the highly pathogenic avian influenza infections — the first in cattle in the state — have been discovered by testing in the past week.

The two most-recent detections were in Sioux County, in herds with 1,700 and 250 cows . The first was an O’Brien County herd with 4,500 cows.

IDALS recently began to require surveillance testing at dairy farms that are within 20 kilometers of an infected poultry site, but all of the herd confirmations so far have resulted from dairy operators notifying the department about their sick cows, said Don McDowell, an IDALS spokesperson.

The virus has been circulating widely among wild birds for the past two years and, until recently, mostly affected domestic poultry flocks. But in March, testing confirmed that Texas dairy herds had been infected by it. Since then it has spread to at least 11 other states, including Minnesota and South Dakota.

Infected cattle have large amounts of the virus in their milk but little elsewhere in their bodies. They typically recover from infections within two weeks. However, the virus is often fatal for domestic poultry flocks. Entire flocks are culled to prevent its spread.

Before the recent detections in Iowa dairies, the virus was found in two poultry flocks — one had 4.2 million egg-laying chickens in Sioux County , and one had 103,000 turkeys in Cherokee County.

Testing has confirmed that the version of the virus that has been infecting cattle also infected at least one of those poultry flocks. It has been shown to transmit from cows to poultry and to people.

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