OMAHA (DTN) -- There is another twist in the investigation of highly pathogenic avian influenza (HPAI) in dairy cows.

Samples tested by the Food and Drug Administration (FDA) showing remnants or fragments of HPAI in pasteurized milk indicate the H5N1 virus has spread across more dairy herds than federal investigators have discovered.

In a statement Tuesday, FDA explained samples of pasteurized milk had tested positive for the virus, though the agency said the findings "do not represent actual virus that may be a risk to consumers." FDA added, "To date, we have seen nothing that would change our assessment that the commercial milk supply is safe."

FDA and USDA had initially said the virus had not entered the commercial milk supplies because milk from sick cows was being destroyed. FDA's statement Tuesday stressed that pasteurization is generally expected to eliminate pathogens to a level that does not pose a risk to consumer health.

"While milk is pasteurized, not sterilized, this process has helped ensure the health of the American public for more than 100 years by inactivating infectious agents," FDA stated.

So far, USDA's National Veterinary Services Laboratories has confirmed 33 dairy herds in eight states have been infected. The latest was another Idaho dairy on April 19.

However, there have been concerns because some cattle have tested positive for HPAI but have been asymptomatic as well.

As DTN noted Tuesday, USDA's lack of information shared about the outbreak is drawing fire from researchers who say the department is not providing enough information for them to research the spread of the virus.

"In an obscure online update this week, the Department of Agriculture said there is now evidence that the virus is spreading among cows and from cows to poultry," the New York Times reported.

So far, the HPAI outbreak in cattle has not had a major impact on dairy prices, though DTN's Opening Dairy Comments on Wednesday noted, "Milk futures took a hit Tuesday with overnight trading activity showing further selling pressure. Overnight trading volume has been increasing recently, which may be an indication of greater volatility this year."

FDA on Tuesday stated, "Some samples collected have indicated the presence of HPAI" but did not indicate how many samples of pasteurized milk were taken. The agency is now increasing its efforts to test more milk, including more testing "that is representative of real-world scenarios in which milk is typically pooled in large amounts from numerous healthy cows from numerous farms before pasteurizing and processing."

FDA added, "Work is underway to test samples of milk in systems that represent current industry practices using the range of temperature and time combinations that are used in pasteurization processes."

The National Milk Producers Federation and International Dairy Foods Association issued a joint news release Tuesday, noting "FDA reaffirms that pasteurization is effective against HPAI; the commercial milk supply is safe."

NMPF and IDFA stated, "The data cited by FDA is consistent with many other studies demonstrating that the legally required temperature and time for milk pasteurization will readily inactivate HPAI. Viral fragments detected after pasteurization are nothing more than evidence that the virus is dead; they have zero impact on human health. Further, the federal PMO (pasteurized milk ordinance) prohibits milk from sick cows from entering the food supply chain. Milk and milk products produced and processed in the United States are among the safest in the world."

The groups added, "We encourage the FDA to continue to gather scientific data and information, consistent with its plans."

FDA and dairy groups also cautioned again about the risks of consuming raw milk -- which has not been pasteurized.

"Because of the limited information available about the possible transmission of H5N1 virus via raw milk, the FDA continues to recommend that the industry does not manufacture or sell raw milk or raw milk products, including raw milk cheese, made with milk from cows showing symptoms of illness, including those infected with avian influenza viruses or exposed to those infected with avian influenza viruses," FDA stated.

FDA also recommended farmers take precautions to discard milk from affected cows, so the milk does not become a source of further spread. That includes taking precautions to heat the milk even though it is being dumped.

"Any raw milk or milk products from exposed cattle that are fed to calves (or to other animals, such as farm cats) should be heat treated or pasteurized," the FDA stated.

Full FDA update https://www.fda.gov/…

See, "Scientists, Others Question USDA's Information Sharing About H5N1 in Dairy Cattle," https://www.dtnpf.com/…

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

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