USDA Confirms Cow-to-Cow Transmission of Avian Flu in Dairy Herds

The U.S. Department of Agriculture (USDA) has confirmed that cow-to-cow transmission is contributing to the spread of avian flu within dairy herds. While the precise mechanisms of transmission remain under investigation, the discovery marks a significant development in understanding the virus’s behavior.

Farmers and veterinarians have been seeking clarity on transmission routes to improve control measures. Avian flu outbreaks have been detected in dairy herds across eight states in the past month, with one dairy worker in Texas also testing positive.

“Those of us that have worked with influenza for a long time were fairly quickly saying, ‘Yep it moves cow-to-cow,'” said Jim Lowe, associate dean at the University of Illinois College of Veterinary Medicine. “You can’t explain the epidemiology any other way.”

Wild migratory birds are believed to be the primary source of the virus. However, USDA investigations indicate that cattle movements between herds and potential transmission from dairy premises to nearby poultry facilities are also playing a role.

The USDA reports that infected cows shed the virus at high levels in their milk, raising concerns about the potential for transmission through unpasteurized milk. While respiratory transmission is not believed to be the main route of infection among cattle, it appears to primarily affect older cows, though younger cows have also been infected.

Despite the ongoing questions, the USDA has opted not to impose quarantines restricting cattle movement around affected dairy farms, unlike the strict measures enforced for poultry facilities. Infected cattle typically recover, whereas avian flu is often fatal for poultry.

The USDA emphasizes that reducing cattle movement, testing animals before transport, and implementing rigorous farm cleaning procedures can help mitigate the need for regulatory restrictions.

Currently, confirmed cases of HPAI in domestic livestock have been reported in Idaho, South Dakota, Kansas, New Mexico, Texas, Michigan, Ohio, and North Carolina.