DES MOINES, Iowa (DTN) -- USDA is planning to test raw bulk milk nationally for the H5N1 bird flu virus because of the growing number of cases during the past month in California dairy herds and the finding of a different strain of highly pathogenic avian influenza on a small Oregon farm that infected at least one pig.

Agriculture Secretary Tom Vilsack spoke to reporters Thursday at the World Food Prize's Borlaug Dialogue about USDA's plans to expand the testing of milk across the country. He also explained that the strain of highly pathogenic avian influenza virus found on an Oregon farm is different from the H5N1 strain that has swept through dairy herds this year.

USDA will begin broader bulk testing of vats or silos at milk processors in November for states such as California that now have the virus.

Since the outbreak began in dairy herds in March, there have been 404 herds hit by the virus in 14 states. California accounts for half of those infected herds -- 202 dairies -- with 158 confirmed cases in the past month alone.

California is the country's largest milk-producing state and accounts for roughly 20% of the country's milk and dairy products.

Vilsack said milk testing often can provide signs that the virus is in a dairy herd before any cows show symptoms. Sometimes cows are also asymptomatic but still carrying the virus.

"We know from some advanced research that when you test the milk it gives you an indication that the virus is there even before you see it in the cows," Vilsack said. "So, testing will give us an opportunity to get ahead, if you will."

OREGON SWINE CASE

USDA's Animal and Plant Health Inspection Service (APHIS) on Wednesday also announced the finding of "H5N1" on an Oregon farm that included at least one pig that tested positive for the virus. Vilsack said that the strain of virus is different from the virus found in dairy cattle.

"The Oregon situation is a little bit different," Vilsack said. While it is H5N1," Vilsack noted, "It's more hi-path (highly pathogenic). It was more the result of wild birds."

Vilsack said there are different variations of virus strains. The Oregon strain was not the same as in dairy cattle or in a lot of the poultry cases. "We tested the poultry. Clearly, they had the virus. That led us to test the swine."

A spokesperson for USDA said genetic sequencing for the pig is still underway. Analysis of the poultry on the farm indicates the virus is consistent with other strains associated with wild birds. "It is H5N1, but not the strain that's been associated with cows," the spokesperson stated to DTN.

USDA will follow up with more detail when the testing results are complete, including results for the other two pigs and what is learned from further sequencing. "Yesterday we wanted to get the update out with as much as we could at the time," the spokesperson stated.

Vilsack said the Oregon farm "was a very small operation," with 70 birds and a couple of swine. "And one of the swine obviously had the virus, and that's obviously the first time we've had to deal with this. So, it's significant -- important for us to know. But it's not related to the dairy situation."

There also was a commercial poultry flock in Oregon that was affected by this outbreak.

"The other important factor in all of this is we're getting back into the migratory season where the birds are flying," Vilsack said.

With Iowa as the country's largest pork producer, Vilsack was asked if swine producers should be doing anything to respond.

"First of all, let's make sure everybody understands the milk is safe, the beef is safe, the pork is safe. There's no issue relative to the food supply. And at this point in time, there's nothing for Iowa producers to do. It's important for them to know this happened, but there's nothing for them to do. Pork producers deal with a variety of viruses on an ongoing basis."

EXPANDED DAIRY TESTING

California has not yet implemented bulk-milk testing but was preparing to start testing in the Central Valley where the infected farms are concentrated. Vilsack indicated USDA and the California Department of Food and Agriculture (CDFA) would test California's milk at processors statewide.

Beyond California, Vilsack said USDA would start with more bulk-milk testing in all 14 states where farms have tested positive for the virus. USDA would then look at expanding that testing "strategically in a tiered state way" to ultimately get to all 50 states, Vilsack said.

"There will be multiple stages here. We test the silos. If it turns out that there is a virus, we'll then begin the process of going to more specific testing -- bulk-tank testing on farms, so that we can identify exactly where the virus could be."

USDA will pay for the cost of sampling, shipping and testing, he said. USDA is still putting together formal guidance on how the testing will work. He said that will require working with state departments of agriculture and veterinarians to get their input on how to fully implement the testing process. Vilsack suggested there could be some reluctance from some state officials or industry.

"I think we're going to find there's a genuine desire and interest to do this on the part of most folks and to be able to, hopefully over time, begin the process of replicating what we have in Colorado."

Ideally, Vilsack said, if all 50 states are testing, "we can certify to the rest of the world that we're virus-free."

CALIFORNIA CASES CHANGE DYNAMICS

When H5N1 first showed up in a Texas dairy herd in March, USDA opted to "respond and react as the situation evolves and changes," Vilsack said.

"We've obviously recently seen the introduction of H5N1 in California and for a period of time we thought it was relatively contained in that state," Vilsack said. "But we've obviously seen recently a significant number of increases in the number of herds that have been impacted and affected despite efforts on the part of California."

Vilsack indicated the volume of dairies affected in California called for aggressive surveillance measures and he pointed to Colorado's work to control the virus. When Colorado's dairy herds were hit with the virus in August, Vilsack said the state instituted a "fairly aggressive testing regime" that allowed Colorado officials to identify precisely where the virus was located. That allowed both veterinarians and farmers to implement more advanced biosecurity measures on farms. "And as a result, they are now virus-free."

He added, "At the same time, we have a more intense concentration of dairy operations in California and we are continuing to see more herds impacted."

Combined with the highly pathogenic avian influenza cases at the Oregon farm, this led USDA to look at how the agency "might ensure that states are in fact virus-free and how we might be able to identify states that are not."

Along with more national bulk testing, USDA continues to work on developing a vaccine for H5N1. The secretary said when he left the World Food Prize event that he was going to the USDA National Animal Disease Center in Ames, Iowa, to get briefed on work to develop a vaccine.

Also see "USDA Confirms First US Case of Bird Flu in Swine at Oregon Backyard Farm," https://www.dtnpf.com/…

Chris Clayton can be reached at Chris.Clayton@dtn.com

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