Agriculture officials throughout the West are continuing to find new cases of highly pathogenic avian influenza in wild and domestic birds, dairy cattle and even swine, prompting the USDA to ramp up testing and monitoring for the virus.

The agency’s Animal and Plant Health Inspection Service is working with state veterinarians to collect raw milk samples to better assess where the H5N1 virus is present, with the goal to better inform biosecurity and containment measures. Colorado is already doing such testing, and the USDA has used bulk milk testing to eradicate brucellosis from dairy herds.

APHIS has also approved field trials for several possible vaccines for H5N1 in cattle and other species, and health officials are telling farmers that biosecurity is their best weapon against the spread of the disease.

“Avian influenza is a very serious disease with serious implications for animal welfare,” said Amber Itle, Washington’s state veterinarian. “It’s crucial to stay alert for any sudden illness and deaths in your flock and take steps in biosecurity.”

The measures come as the virus that has been devastating farm animals since 2022 shows few signs of abating. The flu is widespread in wild birds worldwide and is causing outbreaks in poultry and U.S. dairy cows with several recent human cases among U.S. dairy and poultry workers, warns the U.S. Centers for Disease Control and Prevention.

Related:HPAI is spreading in California dairy herds

Oregon recently recorded the first known case of H5N1 in a pig. The hog was part of a non-commercial backyard farm in Crook County, Ore., east of Bend, at which officials also euthanized 70 infected birds, according to the Oregon Department of Agriculture. The livestock and poultry on this farm shared water sources, housing and equipment, APHIS said.

New detections

Elsewhere in the West:

California has been the epicenter of the current outbreak in dairy cattle, with 278 Central Valley dairies seeing infections this fall as of Nov. 12, according to the state Department of Food and Agriculture.

State health officers have confirmed 21 human cases in California, with all of them having contact with animals at different farms and experiencing mild symptoms such as conjunctivitis. There have been 46 confirmed human cases nationwide, including 11 in Washington and nine in Colorado who were exposed to infected poultry, the CDC reports.

Related:U.S. spots first bird flu case in swine

Nationwide, HPAI has affected 105.2 million poultry, been confirmed in 10,563 wild birds and infected 492 dairy herds as of Nov. 12, according to the CDC. In the West, infected dairy herds have been reported in Colorado (64 cases), Idaho (35 cases), Utah (13 cases), New Mexico (nine cases) and Wyoming (one case), the USDA reports.

Spread from farm to farm

USDA data collected over the past seven months has shown that H5N1 can be transmitted on equipment, people or other items that move from farm to farm, including between dairies and poultry facilities. A federal requirement to test cattle before movement between states has curbed the spread, but officials say local and state biosecurity efforts are just as important.

Anja Raudabaugh, chief executive officer of Western United Dairies, said recently that farms are taking myriad biosecurity measures, including:

WUD has been handing out free PPE and passing on resources and information, including on a dedicated website, Raudabaugh said.

This summer, California’s Department of Public Health handed out protective equipment for dairy farmworkers and others handling raw dairy products, as well as for slaughterhouse and commercial poultry farmworkers.