USDA aims to isolate, exhaust H5N1 virus in dairy herds

The USDA’s strategy against bird flu in dairy cattle is to identify infected herds and wait for the virus to die out within the herds, said Agriculture Secretary Tom Vilsack on Monday. “I’m confident we have a good understanding of the virus and how it is being transferred,” he added.

“We are trying to essentially corner the virus” within infected herds so it eventually dissipates, he said during a teleconference.

The H5N1 avian flu virus was confirmed in dairy cattle for the first time on March 25 in the Texas panhandle. It was found in eight other states through April 25. No other states have reported an outbreak since then.

Three cases of cattle-to-human infections, involving dairy farmworkers, have been identified. Last week, a farmworker in Michigan was the first to experience respiratory symptoms — a potentially more serious condition. The CDC said genomic sequencing indicated H5N1 remained an avian virus and has not adapted to mammals. The risk to the general public was low, it said; people in contact with infected animals should wear masks, gloves, and other protective equipment.

The government has faced repeated questions about whether it knows for certain how widespread bird flu in cattle is. To date, H5N1 has been confirmed in 80 herds in nine states. The USDA requires dairy farmers to test lactating cows for bird flu before shipping them across state lines. It also offers money to dairy farms to improve their biosecurity standards against disease and will launch a voluntary program for weekly testing of milk samples drawn from bulk storage tanks on dairy farms.

Vilsack said the voluntary testing program was expected to generate more information about conditions in the field. “Literally thousands of tests have been conducted,” he said.

The CDC says it has tested 40 people for bird flu and was monitoring around 300 people, most of them in Michigan, the state with the largest number of infected herds, 23. Idaho is second with 17, followed by Texas with 15.

Over the weekend, the Iowa state Agriculture Department said highly pathogenic avian influenza was discovered on a turkey farm in Cherokee County in northwest Iowa. It was the second outbreak in a week in Iowa. The other was an egg farm with 4.2 million hens. Bird flu has killed 96.6 million birds, mostly hens and turkeys, in U.S. domestic flocks since outbreaks began in February 2022, according to a USDA database.