USDA Creates Milk Testing Strategy to Combat H5n1 in Dairy Cattle

The U.S. Department of Agriculture (USDA) announced a new federal order, as well as accompanying guidance, on December 6 as part of its new National Milk Testing Strategy (NMTS). This builds on measures taken by USDA and federal and state partners since the outbreak of H5N1 in dairy cattle in March.

"This NMTS is designed to increase USDA's and public health partners' understanding of the virus' spread in the United States through a structured, uniform, and mandatory testing system that will help swiftly identify which states, and specific herds within them, are affected with H5N1; support the rapid implementation of enhanced biosecurity measures to decrease the risk of transmission to other livestock; and importantly, inform critical efforts to protect farmworkers to help lower their risk of exposure," according to the announcement.

The federal order has three requirements. First, that raw or unpasteurized milk samples nationwide be collected and shared with USDA for testing to better monitor the spread of the virus in dairy cows.

That encompasses raw milk from any entity responsible for dairy farms, bulk milk transporters or transfer stations, and dairy processing facilities that send or hold milk intended for pasteurization.

Second, the federal order also requires herd owners with positive cattle to provide epidemiological information that enables activities such as contact tracing and disease surveillance.

Finally, similar to USDA's April 24 federal order, it requires that private laboratories and state veterinarians report positive results to the USDA that come from tests done on raw milk samples drawn as part of the NMTS.

The first round of testing under the federal order and the NMTS began December 16 in six states: California, Colorado, Michigan, Mississippi, Oregon and Pennsylvania.

On December 17, the USDA announced that seven more states would be included in the testing strategy: Indiana, Maryland, Montana, New York, Ohio, Vermont, and Washington.

These 13 states represent a geographically diverse mix, some of which have been affected by H5N1 in dairy cows and others that have never detected the disease. Additionally, these states represent eight of the top 15 dairy producing states in the country, accounting for nearly 50% of U.S. dairy production, according to the USDA.

Results from this testing will be included in the routine testing reports shared by USDA's Animal and Plant Health Inspection Service, and any newly affected herds will be reported on the website on the existing HPAI confirmed cases in livestock map.

The USDA announced in late October its plans to implement a tiered strategy to collect milk samples to better assess where H5N1 is present, with the goal to better inform biosecurity and containment measures, as well as to inform state-led efforts to reduce risk to farm workers who may be in contact with animals infected with H5N1. The agency USDA has previously conducted bulk-milk testing approaches, including doing so to eradicate brucellosis from dairy herds. A paper published last March in the Journal of Dairy Science concluded that "testing of (bulk milk) samples can be an important element of infectious disease surveillance programs, particularly if repeated testing is implemented over time."

Dr. Fred Gingrich, executive director of the American Association of Bovine Practitioners, said during the November 20 call with reporters that the virus has demonstrated a remarkable ability to exploit new hosts, underscoring the need for rigorous surveillance and biosecurity.