WASHINGTON —  The U.S. Department of Agriculture plans to embark on a year-long study beginning next month that will test samples for evidence of highly pathogenic avian influenza from former dairy cattle moved into meat production.

Emilio Esteban, the under secretary for food safety at the USDA, told reporters on a call Tuesday the new testing program follows three studies undertaken during the spring and summer that all found beef in the nation’s food supply is safe to eat.

“However, we want to move forward with an additional step,” Esteban said. “And what this means is that when those carcasses are tested, they are held and are not going to go into commerce until we get the results back.”

The virus, also referred to as bird flu or H5N1, has been found in wild bird and domestic poultry flocks within the United States for years. But the ongoing outbreak in dairy cattle has forced animal and human health experts to establish testing for a new community of agriculture workers and livestock.

The news of additional testing for the country’s meat supply came alongside the results of a study from the U.S. Food and Drug Administration that reinforced the safety of pasteurized dairy products.

Steve Grube, chief medical officer for the FDA’s Center for Food Safety and Applied Nutrition, said that the most recent round of dairy product testing included 167 foods that were processed in 27 states in June and July.

“None of the product samples contained viable H5N1, reaffirming that pasteurization is effective,” he said. “The second survey was intended to address geographic and product gaps from the initial sampling of the commercial milk and dairy product supply that the FDA conducted during April and May.”

Testing milk in bulk tanks

Federal officials have also launched a voluntary program for farmers to test the milk in bulk tanks for H5N1, a step that’s intended to make it easier for them to move their cows between states without having to individually test each one.

Eric Deeble, deputy under secretary for marketing and regulatory programs at USDA, said the department’s Farm Service Agency has approved 23 of the 35 applications it has received so far to help ease the financial burden on dairy farmers who take their herds out of production after testing positive.

The program — known as Emergency Assistance for Livestock, Honey Bees, and Farm-raised Fish — has approved more than $1 million in payments.

The price paid to farmers is based on a formula that includes the price of milk from the preceding month as well as the number of dairy cattle that contract H5N1.

Deeble said on the call with reporters that of the approved applications, a dozen are from Colorado, which has seen a sharp increase in the number of positive H5N1 tests within its dairy industry.

Deeble argued the uptick is due to certain factors within the state and cautioned people against assuming that if testing was increased in other areas of the country, the number of positive H5N1 tests for dairy cattle would spike.

“I don’t think that it is accurate necessarily to extrapolate from the situation in Weld County, Colorado,” Deeble said. “Weld County and Colorado dairy in particular is rather unique in the degree to which the dairies are all closely associated with one another; both spatially and the way in which there is a lot of movement between the facilities.”

“It is a tightly integrated dairy community that’s isolated from much of the rest of the state, and there is a lot of connectivity between the premises in the way in which they use vehicles, support services, milk trucks,” Deeble added.

During the last 30 days, five states have had dairy cattle test positive for H5N1, including Colorado, Michigan, Minnesota, South Dakota and Texas.

Colorado holds a disproportionate number of cases with 26 of the dairy herds to test positive, while the other four states combined hold a total of six herds.

Other mammals diagnosed with H5N1 during the last six weeks are overwhelmingly in Colorado, which has found the virus in house mice, deer mice, domestic cats, a desert cottontail and a prairie vole.

Effect on cats

Public health officials said during the call Tuesday they are beginning to look more closely at when and why cats are being affected by the spread of H5N1.

Barn cats as well as those that hunt outside, coming into regular contact with wild birds that hold a reservoir of H5N1, have tested positive for the virus before.

But a report from the Colorado Veterinary Medical Association earlier this month noted that two of the six cats diagnosed with H5N1 in that state this year “were indoor only cats with no direct exposures to the virus.”

Public health officials on the call were unable to answer a question about how indoor-only cats would have come into contact with H5N1.

Experts on the call cautioned that as fall approaches, wild birds will begin migrating and dairy farmers will likely ship their cattle at higher rates, both of which could lead to an uptick in the number of positive cases of H5N1 being reported in dairy cattle as well as other animals.

Lia Chien contributed to this report.