By Tom Polansek
CHICAGO (Reuters) – Migratory waterfowl are to blame for widening avian-flu outbreaks in Texas cows and poultry, and wild birds carrying the virus should be heading north soon, state Agriculture Commissioner Sid Miller said on Tuesday.
The U.S. government since last week has reported cases of the disease in seven dairy herds in Texas and one person who had contact with cows, making it the state most affected by the country’s first-ever outbreaks in cattle. Texas is the biggest U.S. cattle producer.
The cases in dairy cattle and the second human case in two years in the United States renewed concerns about the virus, which has been infecting poultry flocks and a growing number of other species globally since 2022.
A positive test at a Texas egg farm led egg producer Cal-Maine to cull 1.6 million laying hens, the company said on Tuesday. Texas had never before suffered such a major outbreak at a commercial poultry facility, Miller said.
“This is spread by waterfowl,” he said in an interview. “It’s migratory season.”
The U.S. Department of Agriculture (USDA) first reported on March 25 that a cow and milk from two dairies in Texas tested positive for bird flu, with along milk from two dairies in Kansas. The agency later confirmed positive tests in additional dairy herds in Texas, New Mexico, Michigan and Idaho.
The strain of the virus found in the subsequent states is very similar to the strain confirmed in the initial cases in Texas and Kansas that appear to have been introduced by wild birds, the USDA said.
“We’re ready for the ducks to head north to their nesting grounds,” Miller said. “We think within a week or a little longer they’ll all be out of Texas and we’ll be out of the woods.”
USDA said that transmission of the disease between cattle cannot be ruled out.
The U.S. Centers for Disease Control and Prevention considers the risk of bird flu for humans to be low. The Texas patient’s only symptom was eye inflammation, according to the state’s health department.
Richard Webby, a virologist at St. Jude Children’s Research Hospital in Memphis, said testing for flu in cattle is not routine and that it was important to establish the connection between the sickness in cows, and ducks and cats on the farms.
“Some smart people made the link and actually tested them for flu,” he said.
With these cases, people will start looking for similar events in Europe and Asia, said Webby, director of the WHO Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds.
The Texas outbreak may have started about a month ago when a mysterious illness affected about 40% of the state’s dairy herds, Miller said. He said he now suspects it was bird flu, though officials did not know it at the time and can’t confirm it because the animals recovered.
“We were testing for every cattle disease we could think of and then somebody said, ‘What are all these dead birds doing around the dairies?'” Miller said.
