Updates on Highly Pathogenic Avian Influenza Virus (HPAIV) H5N1

By Ed Maltby, NODPA Executive Director

H5N1 is here to stay, and the federal government is not doing anything different, despite continued outbreaks with both poultry, livestock and humans. The Trump administration’s intention is to combat avian flu in poultry by moving away from mass culling of infected flocks and prioritizes enhanced biosecurity measures and medication to control the spread of the virus.

The Secretary of Agriculture is currently re-evaluating the use of vacines. In a statement to Agri-Pulse on March 4th 2025, Rollins says the five-pronged approach to bird flu includes “efforts to explore vaccines, therapeutics, and other strategies to protect egg-laying chickens and reduce depopulation. “USDA is taking a targeted, science-driven approach to developing next-generation solutions and will invest up to $100 million to determine the best path forward. A formal public solicitation will be issued in the coming week. Vaccine and therapeutics strategy, logistics, and surveillance … are critical steps in advancing this effort.”

There is nothing specific about enhanced biosecurity for poultry, which currently appears at an all-time high, but dairies need to upgrade their systems, especially to protect humans. In launching a $1 billion, five-stage strategy aimed at curbing the spread of H5N1to protect the U.S. poultry industry, there was no mention of any new policy or allocation of funds for dairy. The USDA’s Secretary of Agriculture’s suggestion is to get your own backyard chicken if you want to combat the high price of eggs. Perhaps you also need your own house cow as well!

The US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) recently confirmed an H5N1 detection in Idaho dairy cattle, the state’s first since October. Since early 2024, APHIS has reported 977 H5N1 detections in dairy cattle from 17 states of which 730 have been in California, where 70% of the herds have dealt with H5N1, and milk production fell by 9.3% in November. Since February 1, 2025, 36 new cases of H5N1 in dairy cows have been reported, including the first cases in Nevada and Arizona. The costly financial and milk production consequences of H5N1 infections in US dairy have been laid bare in new research (https://www.dairyreporter.com/Article/2025/03/18/a-ton-of-milk-per-cow-lost-in-bird-flu-stricken-herd-study/ ). Economic losses due to decreased milk production,mortality and early herd removal were estimated at $950 per clinically affected cow for a total cost of approximately $737,500 for the herd during the observation period. Research results demonstrate a long-lasting production impact and signifi cant financial consequences of HPAI H5N1 virus infection to dairyfarms. Research dcument available at: : https://www.researchsquare.com/article/rs-6101018/v1 .

Human infections

The outbreak has infected dozens of people, mostly farm workers. So far, most people infected experience mild illness and eye inflammation, and the virus is not spreading between people. The first H5N1 death in the US was reported in January 2025 following exposure to infected chickens. One of the earliest strains of avian influenza isolated from a human in Texas shows a unique collection of mutations that enables it to more easily replicate in human cells, researchers from Texas Biomedical Research Institute (Texas Biomed) reported in Emerging Microbes & Infections. The finding highlights a key concern about the H5N1 strains of avian influenza currently circulating in the U.S., the speed at which the virus can mutate when introduced to a new host.

Vaccine for dairy cattle

A new study indicates that HPAI is more prevalent in dairy cows than previously reported. Scientists have identified a concerning genetic mutation, PB2 E627K, in four dairy cow herds nearly a year after the virus was first detected in Texas. This mutation, linked to increased mammal-to-mammal transmission, was also found in the firts humand case last March. While the USDA is not changing its policy on dairy cows infected by H5N1 or seemingly trying any new approaches, Elanco Animal Health has signed an agreement with South Dakota biotech firm Medgene to commercialize its bird flu vaccine in cattle. An Elanco press release says the Medgene vaccine is in the final stages of review for a conditional license and has met USDA’s platform technology guidelines. Injecting dairy cattle with a vaccine will be far easier than with poultry and will not have any effect on exports of dairy product. Dairy organizations back vaccine use to control the virus. It is uncertain

The American Dairy Coalition has published the following information from their December 18, 2024 webinar about the learning curve for H5N1 in dairy:

Cows shed the virus up to 16 days before clinical signs.
Producers report 30 to 40% herd level milk production loss that comes back about halfway after six to eight weeks (time shaved off peak production); some next lactation impacts are emerging as the udder has receptors for the virus, and infection can cause scarring.
Virus does not discriminate - young cows and older cows, all stages of lactation; even dry cows with collars showed the same drop in rumination minutes.
Mortalities increased by 1.5 to 2% at the herd level.
Longer term impacts of early culling, aborted pregnancies; other reproduction issues emerging.
Primary spread of virus between herds comes from cattle movement, shared equipment, shared personnel.
Mechanisms of spread within herds include direct cow-to-cow contact, milking machines, and respiratory spread.
Some producers found that identifying sick cows early via forestripping to check for discolored milk and immediately pulling them into a separate milking group can slow the rate of spread within the herd.
Work with your herd vet on supportive care, but producers found supportive therapies generally do not change outcomes, fever lasts 2 to 3 days.
Balance reduction of external stress to sick cows with stress to labor. Producers found that if weather is good, it may be best to do less interaction with the cows to reduce their stress and the labor stress; let them rest in clean comfortable area; consider letting virus run its course with less interactions, except for the very sick; consider reducing milking frequency temporarily for those cows alongside the drop in milk production; consider strategic culling of already identified DNB's (do-not-breeds) if you learn your herd tested positive in bulk milk sampling.
Bed with straw and/or provide plenty of loose hay close to sick cows in the pen as this is what they will more likely eat when rumination and intakes drop.
Further support rumen with fresh feed, frequent pushups, and consider prebiotics and probiotics.
Have a plan for how cows will be identified (i.e. forestripping check for discolored milk); where sick cows will be housed and treated, and have a treatment plan.
Keep records (ELAP indemnity for milk loss), number of impacted cows per month removed or deviated, milk production records (verifies drop).
Unaffected herds minimize risk by having a biosecurity plan; limiting herd introductions, especially lactating cows, testing before introduction; using quarantine periods; testing heifers returning from off-site; restricting traffic and visitors (parking area by office); limiting crossover of dairy workers with domestic poultry exposure; wearing gloves, washing hands, protecting eyes and face; keeping work clothing and boots onsite.

Posted: to Industry News on Sat, Mar 15, 2025
Updated: Tue, Mar 18, 2025