Highly Pathogenic Avian Influenza in Ruminants

Press Release

5/22/2024 - Recommendations to Minimize Influenza Transmission at Dairy Cattle Livestock Exhibitions

On Friday, March 29, USDA APHIS confirmed the detection of highly pathogenic avian influenza (HPAI) in dairy herds, with confirmations now in Texas, Kansas, Michigan, Idaho, New Mexico, Ohio, North Carolina, and South Dakota. On Wednesday, April 24, the Animal and Plant Health Inspection Service (APHIS), United States Department of Agriculture

(USDA), is issuing this Federal Order to prevent the spread of highly pathogenic avian influenza (HPAI). The federal order will become effective on Monday, April 29, requiring pre-movement testing for HPAI on lactating cows in intrastate commerce. A Guidance document for the implementation of the order is expected to be issued on Thursday, April 25, 2024.

Although the mechanics are unclear, APHIS will provide reimbursement for testing at NAHLN labs, including samples submitted for:

(1) dairy cattle suspected of disease due to clinical signs,

(2) pre-movement testing,

(3) producers interested in the disease status of their asymptomatic animals, and

(4) samples taken from other animals on dairies associated with this disease event.

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.

A review of H5N1 in livestock includes:

  • Decreased herd level milk production;
  • Acute sudden drop in production with some severely impacted cows experiencing thicker, concentrated, colostrum-like milk;
  • Decrease in feed consumption with a simultaneous drop in rumen motility;
  • Abnormal tacky or loose feces, lethargy, dehydration, and fever.
  • Initial cases indicated older cows in mid-lactation may be more likely to be severely impacted than younger cows and fresh cows or heifers. Additional data indicates younger cattle have been affected; more data and reporting from impacted producers will help to clarify the range of animals affected.


USDA believes that transmission among cows is via mechanical transmission of milk, possibly in a parlor setting where cows are in close proximity to one another, as well as milking equipment. Furthermore, biosecurity breeches where animals, people, and fomites such as equipment, are moved from farm-to-farm.


  • Wild migratory birds are believed to be the source of initial infection via spill over event(s). Transmission between cattle has been confirmed, as well as movement from lactating dairy cows back to poultry.
  • Limited movement of lactating, or about to lactate, animals is key, as well as isolating moved animals from resident herd. Cows moved from Texas to other states are the source for the virus in those new states.
  • One Texas dairy worker has been confirmed positive with HPAI. Initial testing has not found changes to the virus that would make it more transmissible to humans. While cases among humans in direct contact with infected animals are possible, this indicates that the current risk to the public remains low.
  • There are no markers known to be associated with influenza antiviral resistance found in the virus sequences from the patient’s specimen and the virus is very closely related to two existing HPAI A(H5N1) candidate vaccine viruses that are already available to manufacturers, and which could be used to make vaccine if needed.
  • If swabs for conjunctivitis are submitted for testing, the swabs must be sent to CDC in Atlanta because a validated test for the State Hygienic Lab to run.
  • It is important to note that “highly pathogenic” refers to the severe impacts to birds, not necessarily in humans.


  • At this time, there continues to be no concern that this circumstance poses a risk to consumer health, nor does it affect the safety of the interstate commercial milk supply because products are pasteurized before entering the market. Only milk from heathy animals is authorized for distribution into interstate commerce for human consumption, additionally pasteurization has continually proven to inactivate bacteria and viruses, like influenza viruses, in milk and milk products such as cheese.2
  • Based on the limited research and information available, we do not know at this time if HPAI A (H5N1) viruses can be transmitted through consumption of unpasteurized (raw) milk and products (such as cheese) made from raw milk from infected cows. However, we have long known that raw milk can harbor dangerous microorganisms (germs) that can pose serious health risks to consumers.
  • Studies are ongoing to determine if the PCR positives of H5N1 in milk on the retail shelves are actually infectious. Initial tests done at NIAID lab(s) indicate it is not infectious.

As of Friday, April 12, the Iowa Department of Agriculture and Land Stewardship is not aware of any cases of HPAI in dairy cattle or poultry in Iowa. Other states, including Texas, Kansas, New Mexico, Idaho, Michigan, Ohio, North Carolina, and South Dakotahave all reported cases in recent days or weeks. Several states have recently reported cases of HPAI in commercial or backyard poultry. Iowa’s last case in a commercial poultry flock was reported on November 23, 2023. Iowa’s last case in a backyard poultry flock was reported on December 19, 2023. Though a recent case of HPAI was confirmed in a dairy work in Texas, the Centers for Disease Control (CDC) continues to believe the threat to humans remains low.

Heightened Biosecurity Protocols and Practices

With spring migration in full swing, the Iowa Department of Agriculture and Land Stewardship is strongly reminding Iowa poultry producers and dairy farmers to bolster their biosecurity practices and protocols to protect their flocks and herds. The Iowa Department of Agriculture and Land Stewardship has biosecurity recommendations for dairy herds to utilize. In addition, the Department has numerous other biosecurity resources for poultry producers and livestock farms to reference on its website.

“Heightened biosecurity on both poultry and cattle farms is critically important to keeping our livestock healthy. We would strongly recommend farmers work with their veterinarian and have a very good understanding of the health status of any herd that they are receiving any cattle from,” said State Veterinarian Dr. Jeff Kaisand. “Veterinarians, poultry producers with sick birds or dairy farmers seeing unusual or suspicious illnesses should report them to the Department at 515-281-5305.”

Report Sick Cattle and Sick Birds

We are strongly encouraging industry partners, farmers and veterinarians to report cattle illnesses quickly to the Iowa Department of Agriculture and Land Stewardship at 515-281-5305 so that we can monitor any potential cases. The list of symptoms in dairy cattle and poultry can be found on the Department’s website.

Food Safety

It is a longstanding practice that only milk from healthy animals may enter the food supply. The pasteurization process of heating milk to a high temperature ensures milk and dairy products can be safely enjoyed. There is no concern about the safety of pasteurized milk or dairy products. Pasteurization has continually proven to successfully inactivate bacteria and viruses, like influenza, in milk. It also remains safe to eat poultry products. As a reminder, consumers should always utilize the proper handling and cooking of eggs and poultry products, including cooking to an internal temperature of 165˚F.

For additional information on HPAI, please visit the Iowa Department of Agriculture and Land Stewardship’s website.


  • On March 25, 2024, USDA announced that it had detected Highly Pathogenic Avian Influenz (HPAI) in Texas and Kansas dairy herds.


  • Dairy producers with affected animals have reported a rapid onset of illness in herds, specifically among older, lactating cows.
  • Clinical signs include the following:
    • Decreased herd level milk production
    • Sudden drop in milk production from individual cows
    • Discolored and thicker milk
    • Decrease in feed consumption
    • Abnormal feces and fever
    • Older cows may be more likely to be severely impacted than younger cows
    • For dairies whose herds have exhibited symptoms, about 10% (on average) of each affected herd has been impacted, with little to no associated mortality reported among the animals.
    • According to dairy farmers and veterinarians reporting on affected herds, most cows recover within two to three weeks with supportive care.
  • Report Sick Cows:
    • We strongly encourage dairy farmers, veterinarians, and other industry partners to quickly report any suspicious cattle illnesses to the Iowa Department of Agriculture and Land Stewardship at 515-281-5305 so that we can expiditiously monitor and respond to any potential cases.
  • Communication and Coordination with Herd Veterinarians
    • We strongly encourage dairy producers to stay in close communication and coordination with herd veterinarians regarding the health status of cattle - especially prior to any movements of animals occurring - and implementation of biosecurity practices.
  • Food Safety
    • At this stage, USDA believes there is no concern about the safety of the commercial milk supply or that this circumstance poses any risk to consumer health.
    • Dairies are required to send milk from only health animals into processing for human consumption.
    • Milk from impacted animals is diverted or destroyed so that it does not enter the food supply.
    • In addition, pasteurization has continually prove to inactivate bacteria and viruses, like influenza, in milk.
    • Pasteurization is required for any milk entering interstate commerce.

The team at the Iowa Department of Agriculture and Land Stewardship will continue to actively monitor this rapidly evolving situation in close collaboration with USDA, other states, and industry stakeholders. Protecting Iowa's livestock farmers from foreign animal disease has been and will continue to be one of Secretary Naig's top priorities for the Department.