HPAI: Avian Influenza in Dairy Cattle

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In late March 2024, the US Department of Agriculture (USDA), the Food and Drug Administration (FDA), and the Centers for Disease Control and Prevention (CDC) issued a statement confirming the identification of Highly Pathogenic Avian Influenza (HPAI) in dairy cattle located in Texas and Kansas. They have suspected that HPAI may be a contributing factor in an unclassified illness affecting older, mid- to late-lactation dairy cattle in several herds in New Mexico, Texas, and Kansas earlier in the year. It is not yet clear if all reports of the unclassified illness are caused by HPAI. Click here to read the original press release.

What is HPAI? This virus is part of a type of Influenza A viruses that primarily affect birds. The highly pathogenic classification is based on the severity of the disease in poultry, but it is not as severe in mammals such as pigs, cattle, or human. The current outbreak in domestic poultry (H5N1) has been occurring since 2022; and it has been reported in 48 states, affecting more than 82 million domestic birds. It is not yet clear if the strain currently affecting dairy cows has spread from the current outbreak in poultry.

Rarely, the HPAI virus can spill over to mammals, including humans, with varying severity of clinical signs. At this point, there is nothing to suggest humans are at an increased risk from this particular strain; and the risk remains very low for human illness. This is only the second time HPAI has been reported in ruminants.

How do cows get the disease? Sporadic outbreaks of HPAI have occurred in commercial poultry operations throughout the country during the last year, including in Ohio. Migrating waterfowl are the reservoirs of the disease and are believed to be the source of the infections in this instance per the USDA. This disease can be devastating to the poultry industry, causing high levels of mortality. However, this does not seem to be the case in dairy cattle where the disease tends to have the following signs:

  • Decreased ruminations, feed intake, and milk production are found in second lactation and older cows typically over 150 days in milk.
  • Milk from affected animals has a thick, yellow, colostrum-like appearance.
  • Manure is typically firm/tacky, and a fever may or may not be present.
  • Typically, 10% of animals in the herd are affected with a peak incidence at 3-4 days and the outbreak lasting approximately 10-14 days.
  • Few if any of the cows die from the disease, with many recovering; although many cows end up being culled due to low production or mastitis.

Is milk and meat safe to eat? Yes! Abnormal milk is not allowed into the supply chain, and the commercial milk supply remains safe thanks to federal animal health requirements and pasteurization. The influenza virus is easily inactivated through pasteurization. Beef is also safe for human consumption if properly handled and cooked. This is not considered a threat to public health.

Additonal Resources

Questions and Answers Regarding Milk Safety During Highly Pathogenic Avian Influenza (HPAI) Outbreaks from the U.S. Food & Drug Administration

Centers for Disease Control and Prevention Report Just One Case of HPAI in a Human