The Dairy Industry's Growing Concern: Influenza A and Its Impact on Dairy Cattle

Influenza A, including highly pathogenic avian influenza (HPAI), has emerged as a significant threat to the dairy industry, with cases detected in dairy cattle across multiple states. While the virus is not typically fatal in dairy cattle, its effects are far-reaching, causing substantial economic and operational challenges for affected farms. Infected cows often experience a significant drop in milk production, and some become seriously ill, leading to increased costs and reduced productivity. Pennsylvania, a state with numerous multi-species farms that house both poultry and dairy operations, is particularly vulnerable. The ease with which Influenza A spreads between animals and farms underscores the urgent need for robust biosecurity measures to prevent widespread outbreaks.

How Does Influenza A Spread in Dairy Cattle?

The initial introduction of Influenza A into dairy herds in the Southwestern U.S. is believed to have occurred through infected wild birds. Since then, the virus has primarily spread through cow-to-cow transmission, facilitated by the movement of lactating dairy cows, contaminated equipment, and people traveling between farms without adhering to biosecurity protocols. The virus can be transported via trucks, farm equipment, clothing, footwear, tools, and even humans. To mitigate this risk, farms must implement strict biosecurity measures, such as wearing designated boots, using disinfectant footbaths, cleaning equipment thoroughly, and disinfecting vehicle tires. Penn State Extension and the Center for Dairy Excellence (CDE) is offering support to dairy producers in developing and maintaining effective biosecurity plans.

Pennsylvania's Proactive Response: Mandatory Milk Testing

In response to the rapid spread of HPAI in dairy cattle across the U.S., the Pennsylvania Department of Agriculture (PDA) implemented mandatory milk testing at no cost to producers in November 2024. This initiative aims to detect the presence of Influenza A/HPAI in lactating dairy cattle and prevent potential cross-species transmission to poultry, which could result in devastating losses for both industries. The testing program, which begins at the processor level, requires milk processors and dairy farms to collect and submit raw milk samples from each compartment of milk tankers every 14 days. Samples must be accompanied by detailed submission forms and sent to designated Pennsylvania Animal Diagnostic Laboratory System (PADLS) labs within 48 hours of collection.

National Milk Testing Strategy: A Coordinated Effort

On December 6, 2024, the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS) announced the National Milk Testing Strategy (NMTS), a comprehensive program aimed at eliminating H5N1 in U.S. dairy cattle. The NMTS complements Pennsylvania's existing testing program and builds on the April 2024 Federal Order requiring mandatory testing for the interstate movement of lactating dairy cattle. The NMTS focuses on testing bulk milk and requires farms, bulk milk transporters, transfer stations, and dairy processing facilities to allow APHIS to test for HPAI upon request. Laboratories and state veterinarians must report positive Influenza A nucleic acid detection results to APHIS, and owners of positive herds are required to provide epidemiological information, including animal movement logs.

The NMTS is structured into five stages:

1. Implementing National Plant Silo Monitoring: Establishing a system to monitor bulk milk at processing plants nationwide.
2. Determining a State’s H5N1 Dairy Cattle Status: Assessing the presence or absence of the virus in each state.
3. Detecting and Responding to the Virus in Affected States: Rapidly identifying and containing outbreaks in states with confirmed cases.
4. Demonstrating Ongoing Absence of H5 in Dairy Cattle in Unaffected States: Ensuring that states without confirmed cases remain free of the virus.
5. Demonstrating Freedom from H5 in U.S. Dairy Cattle: Achieving the ultimate goal of eradicating H5N1 from the national dairy cattle population.

Requirements for No-Cost Mandatory Testing in Pennsylvania

The PDA has outlined specific requirements for the mandatory testing program to ensure comprehensive surveillance and early detection of the virus:

• Sample Collection: Milk processors in Pennsylvania purchasing or receiving bulk raw milk directly from a Pennsylvania dairy farm or milk cooperative must collect samples at the processing plant. For milk delivered to out-of-state processors, samples must be collected by a bulk milk hauler/sampler.
• Testing Frequency: Samples must be collected at least once every 14 days, with initial samples staggered to ensure coverage across all pickup routes within the first 14 days.
• Submission Details: Samples must be submitted in tubes provided by the PDA within 48 hours of collection, accompanied by a PADLS submission form. The form must include the number of farms contributing to the sample, the USDA-issued premises ID of the processing plant, the number of samples, the date of collection, and the name of the sampler.
• Positive Test Protocol: If Influenza A is detected in a milk tanker sample, the processor must provide the PDA with the identification of all Pennsylvania dairy farms included in that tanker within 12 hours. The PDA will then require testing of milk samples from each identified farm.

Consequences of a Positive Test Result

If Influenza A is detected in a milk sample, the affected farm will be placed under an Order of Special Quarantine and identified as an infected premise. An Infected Zone with a three-kilometer radius will be established around the farm, and all lactating dairy herds within this zone will be required to submit milk samples for surveillance. Testing and sampling within the Infected Zone will continue based on epidemiological analyses until the zone is declared safe.

While the quarantined farm will still be permitted to ship milk, it must adhere to strict biosecurity standards to prevent further spread of the virus. PDA will work closely with producers to ensure business continuity while minimizing the risk of transmission to other farms. Milk samples from farms within the Infected Zone may be collected by weighers/samplers, federal or state officials, or accredited veterinarians and must be submitted to the nearest PADLS lab.

Current Status of HPAI in Dairy Cattle

As of December 2024, there have been no confirmed cases of HPAI in Pennsylvania dairy cattle. However, the outbreak has affected 15 states, with a total of 720 confirmed cases reported since the beginning of the outbreak. The implementation of the NMTS and Pennsylvania’s proactive testing program are critical steps in preventing the spread of the virus and protecting the state’s dairy and poultry industries.

The Importance of Vigilance and Collaboration

The dairy industry's vulnerability to Influenza A highlights the critical need for vigilance, proactive testing, and adherence to biosecurity protocols. The economic and operational impacts of an outbreak can be severe, as seen in other states that delayed implementing testing measures. Pennsylvania's mandatory milk testing program, combined with the national efforts under the NMTS, represents a coordinated approach to safeguarding the U.S. dairy industry. By working together, dairy producers, processors, regulatory agencies, and federal authorities can mitigate the risks posed by Influenza A and protect the livelihoods of those who depend on these vital industries.

For more information on sample submission and testing locations, visit the Pennsylvania Animal Diagnostic Laboratory System website at www.padls.agriculture.pa.gov.

Samples should be sent to the Animal Diagnostic Laboratory at 131 Pastureview Rd., University Park, PA 16802, or delivered to the nearest PADLS lab.

Source: USDA APHIS,  www.padls.agriculture.pa.gov