Avian influenza: elephant in the industry?

Right, wrong or otherwise, highly pathogenic avian influenza H5N1 remains a hot topic in the production animal industries.  After detection in dairy cattle across multiple states in March 2024, the U.S. Department of Agriculture implemented a series of testing requirements to document virus movement and prevent further spread. Fast forward to today, as new testing is being rolled out to monitor the status of HPAI in each state, new infections continue to be found in poultry, wild birds and dairy cattle.

Currently, the federal order from the USDA mandates that all lactating dairy cattle crossing state lines have a negative influenza test (milk sample) within seven days of movement.  The number of animals tested depends on the number of cattle moving. Usually, if the group is larger than 30 head, then only 30 head need to be tested.  If the group is smaller than 30 head, every cow in the load needs to be tested. A common example of this in our practice is farms selling lactating cows at out-of-state auctions, both live and online. Note, however, that cull cows going to slaughter are typically subject to a different set of rules and paperwork depending on the state but do not normally need an influenza test as long as they move straight to the packer. Non-lactating dairy cattle (heifers, dry cows, bull calves) are not currently required to have testing before interstate movement.

Another testing option for moving lactating cows includes the Dairy Herd Status Program. This program is for dairy producers who choose to enroll their herds and agree to weekly herd testing of bulk tank milk. To enroll in this program, the dairy producer must submit an application detailing the farm’s protocol for collecting and testing bulk tank milk along with other pertinent farm data. Once approved by the state vet and the USDA vets (in my experience in Minnesota anyway), the herd will then be eligible to submit bulk tank samples for influenza testing. After three consecutive weeks of negative test results for HPAI, the herd will receive a “monitored unaffected herd” status. Continued weekly bulk tank sample testing with negative results and participation in the status program allows the herd to maintain the “monitored unaffected herd” status and move animals interstate without the additional individual animal milk testing. I feel this is a good option for herds moving cows frequently, but I would recommend planning well ahead of time if producers are interested in enrolling. My experience is that the turnaround to get enrolled is a little bit slow (3-4 weeks) but once enrolled, the program is efficient. However, if a farm misses a week of testing, they must reenroll according to the USDA rules.

Now for the latest news you may have heard about.  The USDA rolled out new testing in December 2024 called the National Milk Testing Strategy to provide a way to identify states and herds with H5N1. This program is using a combination of dairy processing plant silo monitoring and state-specific surveillance. It essentially has a 5-point plan: (1) silo monitoring at plants to identify where the disease is located and any trends; (2) developing bulk tank sampling programs in each state based on the results of the national silo results; (3) for states with H5N1 detections, identify cases and implement response measures to reduce virus spread; (4) demonstrate absence of H5N1 in dairy farms in each state through regular bulk tank sampling; (5) demonstrate H5N1 freedom in U.S. dairy cattle through periodic sampling and testing. The USDA began this program by initiating silo testing in a small subset of states. I don’t know the exact specifics of each step or when Minnesota will be enrolled, but I imagine that it will take some time to move through the whole program with all 50 states.

I have also heard that the USDA is exploring cattle vaccines against H5N1, though international trade regulations may heavily influence any adoption of vaccines as a control strategy.

Why does all this matter? HPAI doesn’t appear to be going away any time soon. In fact, new infections in commercial and backyard poultry continue to be found even in the winter. It also has massive implications for our poultry producers. To be clear, for poultry flocks that detect HPAI, depopulation is often the primary method of control, NOT slaughter. This includes commercial flocks and backyard flocks. In fact, since Dec. 1, 2024, approximately 32,000 birds in Wisconsin, 96,000 birds in Minnesota, and 6.6 million birds in Iowa have tested positive for HPAI and many have been depopulated. For the year 2024 in Minnesota, approximately 2.4 million birds tested positive for HPAI. Imagine the financial implications of depopulating 2.4 million birds. Then imagine the mental challenges of caretakers and owners possibly losing that many birds.    

In summary, I’ll leave you with some signs of HPAI:

— Cows: increased respiratory and gastrointestinal disease; though the main complaint has been dramatically decreased milk production and abnormal milk with a thick colostrum-like appearance.

— Cats: neurological disease and unexplained death, usually in multiple cats.

— Poultry: unexplained increase in mortality, decreased egg production, respiratory issues such as gasping or foaming at the mouth, quiet or depressed birds or neurologic signs (twisted necks).

— Human infection: HPAI is considered to be a low risk to the public by the Centers for Disease Control and Prevention, though 10 states have reported human infections.  

Here are some basic biosecurity ideas:

— Wash or change boots between farms and wear gloves; wash hands especially when working in the parlor. Consider changing sweatshirts or coveralls if one spends significant time in parlors. This includes milk haulers, milking system service providers, Dairy Herd Improvement Association testers and others who step on dairies, especially in parlors. The virus is shed in huge amounts in milk so anyone who has contact with milk or milking equipment/areas could potentially spread the virus.  

— Have separate boots and clothes if you have poultry at home and don’t wear those items to dairies. Avoid having ducks or geese, especially if you have poultry because ducks and geese attract wildfowl and increase the risk of HPAI.

— Don’t share trailers, trucks, and other equipment between premises without washing and disinfecting. See https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/livestock/enhance-biosecurity for more biosecurity ideas. Currently, there is still financial support for biosecurity implementation on farms as well as testing (https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/livestock/financial-assistance).

Megan Weisenbeck is one of six veterinarians at Northern Valley Livestock Services in Plainview, MN. She practices primarily dairy production medicine in Minnesota and Wisconsin. Megan can be reached at [email protected].