Scientists urge testing, biosecurity and vaccination debate after H5N1 detections in dairy and poultry

Witnesses told the House Agriculture Subcommittee that highly pathogenic avian influenza (H5N1) has shifted the response calculus for poultry and dairy producers and that testing, biosecurity and possible vaccination strategies must be part of the national response. Dr. Terry Hensley of Texas A&M said Texas A&M, Cornell and Iowa State collaborated using shared samples to demonstrate H5N1 virus in mammary tissue and milk from sick dairy cows; the results were reported to NAHLN and confirmed by the National Veterinary Services Laboratories, and USDA announced the dairy confirmation on March 25, 2024. Hensley said the dairy cases showed a rapid drop in milk production and that the network’s coordinated testing was essential to identify the cause. "For several weeks, our laboratories ran every test that might provide an explanation, but there were no definitive answers," Hensley said. "When dairies reported large numbers of dead birds and cats, the possibility of a connection between highly pathogenic avian influenza and sick cattle was suggested." He described how shared testing led to the detection in mammary tissue and milk. Dr. Annette Jones, California state veterinarian, described how the workload in California surged from about 450 influenza samples per month to about 12,000 samples per month at the peak — more than 25 times normal — and credited NAHLN surge capacity for sending technicians to assist testing. "These technicians performed the same test on the same equipment using the same standard operating procedures at their home lab, they were able to immediately expand our lab capacity," Jones said, noting that network standardization allowed accurate, nearly real‑time reporting from labs in seven other states during the outbreak’s peak. Witnesses told members that NAHLN labs have provided more than a million test results nationwide during the current outbreak. Jones framed the outbreak response as three necessary, concurrent efforts: ongoing testing to track prevalence and mutations; biosecurity to limit spread (movement control, PPE, sanitation and decontamination); and reducing environmental virus load — currently done mainly by euthanasia of infected flocks and allowing herds to develop natural immunity. "Testing alone will not make the virus disappear," Jones said. "Biosecurity is needed, but even the best farm biosecurity will be overwhelmed if there is too much virus being produced by surrounding poultry, wild birds, and dairy cows." She urged that dairy vaccination be explored as an additional tool and said, "If I were a poultry producer, a beef producer, a swine producer, or a dairy producer, I would be banging my fist on the table to vaccinate dairy cattle way ahead of poultry." Panelists and members acknowledged trade sensitivities surrounding vaccination; Maine and other witnesses said vaccine discussions must weigh international trade implications against the urgency of reducing environmental viral load. The session included detailed examples of how testing and lab coordination enabled rapid identification of novel transmission pathways, and witnesses urged sustained funding, workforce support and research to advance diagnostics, surveillance and vaccination options.