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USDA requires influenza testing for movement of dairy cattle

Animal and Plant Health Inspection Service (APHIS) says the new federal order aims to help it ‘get ahead of’ H5N1 in dairy cattle and limit its spread.

Holstein Dairy Cow On Truck
Vadzim Shubich |

The U.S. Department of Agriculture (USDA) will require dairy cattle to receive a negative test for Influenza A virus prior to interstate movement, according to new measures spelled out in a federal order issued April 24 by USDA’s Animal and Plant Health Inspection Service (APHIS). The new rules will take effect on April 29.

The move comes after multiple dairy herds in eight U.S. states have tested positive for the H5N1 avian influenza virus. Some herds tested positive after they acquired cows from affected herds in other states. USDA has identified spread between cows within the same herd, spread from cows to poultry, spread between dairies associated with cattle movements, and cows without clinical signs that have tested positive. USDA said the new actions will “help us get ahead of this disease and limit its spread.”

The following measures will be required:

Mandatory testing for interstate movement of dairy cattle

  • Prior to interstate movement, dairy cattle are required to receive a negative test for Influenza A virus at an approved National Animal Health Laboratory Network (NAHLN) laboratory.
  • Owners of herds in which dairy cattle test positive for interstate movement will be required to provide epidemiological information, including animal movement tracing.
  • Dairy cattle moving interstate must adhere to conditions specified by APHIS.
  • As will be described in forthcoming guidance, these steps will be immediately required for lactating dairy cattle, while these requirements for other classes of dairy cattle will be based on scientific factors concerning the virus and its evolving risk profile.

Mandatory reporting

  • Laboratories and state veterinarians must report positive Influenza A nucleic acid detection diagnostic results (e.g. PCR or genetic sequencing) in livestock to USDA APHIS.
  • Laboratories and state veterinarians must report positive Influenza A serology diagnostic results in livestock to USDA APHIS.

Updates from USDA

On April 16, APHIS microbiologists identified a shift in an H5N1 sample from a cow in Kansas that could indicate that the virus has an adaptation to mammals. Centers for Disease Control and Prevention (CDC) conducted further analysis of the specimen sequence, which did not change its overall risk assessment for the general public, because the substitution has been seen previously in other mammalian infections and does not impact viral transmission. Additionally, APHIS’ National Veterinary Services Laboratories found H5N1 in a lung tissue sample from an asymptomatic cull dairy cow that originated from an affected herd and did not enter the food supply.

USDA said the novel movement of H5N1 between wild birds and dairy cows requires further testing and time to develop a critical understanding to support any future courses of action. This federal order is critical to increasing the information available for USDA. Requiring positive test reporting will help USDA better under this disease and testing before interstate movement will limit its spread.

“While we are taking this action today, it is important to remember that thus far, we have not found changes to the virus that would make it more transmissible to humans and between people. While cases among humans in direct contact with infected animals are possible, our partners at the U.S. Centers for Disease Control and Prevention (CDC) believe that the current risk to the public remains low,” USDA said on its website. “Additionally, we continue to see affected cows recover after supported care with little to no associated mortality. We also continue to work with our partners in the states and industry to emphasize the critical importance biosecurity plays in limiting disease spread for all livestock and poultry.”

In an update this week, U.S. Food and Drug Administration (FDA) said tests have indicated the presence of avian influenza (AI) virus in pasteurized milk, but says it believes pasteurized milk is safe for human consumption and will conduct further testing. Pasteurization is likely to inactivate the virus, FDA said, however the process is not expected to remove the presence of viral particles. Therefore, some of the samples collected have indicated the presence of AI using quantitative polymerase chain reaction (qPCR) testing.

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