Threat to US dairy cattle: Screwworm moves closer, first HPAI case in Nebraska
A new case of the New World Screwworm has been confirmed by Mexico on 21 September in Sabinas Hidalgo in the state of Nuevo León, less than 70 miles (about 112 km) from the US-Mexico border. Also, a recent case of highly pathogenic avian influenza (HPAI) H5N1 has been confirmed in a dairy cattle herd in Nebraska.
According to the USDA, this is now the northernmost detection of New World Screwworm during this outbreak, and the one most threatening to the American cattle and livestock industry.
Protecting from New World screwworm a priority
“Protecting the United States from New World Screwworm is non-negotiable and a top priority of the Trump administration,” said US Secretary of Agriculture Brooke L. Rollins, adding, “This is a national security priority. We have given Mexico every opportunity and every resource necessary to counter New World Screwworm since announcing the New World Screwworm Bold Plan in June 2025. Nevertheless, American ranchers and families should know that we will not rely on Mexico to defend our industry, our food supply, or our way of life.”
In the most recent case, Mexico’s National Service of Agro-Alimentary Health, Safety, and Quality (SENASICA) has indicated that an affected animal – an 8-month-old cow – had recently been moved to a certified feedlot in Nuevo León from a region in southern Mexico with known active New World Screwworm cases.
The USDA added that prior to this, the northernmost detection was reported on 9 July 2025 in Veracruz, approximately 370 miles (just under 600 km) farther south.
“We are firmly executing our 5-pronged plan and will take decisive action to protect our borders, even in the absence of cooperation,” said Secretary Rollins.
USDA’s eradication plans include:
- The USDA has begun construction on a domestic sterile fly dispersal facility at Moore Air Force Base in Edinburg, Texas. This US$8.5 million facility, expected to be substantially complete by the end of 2025, will be capable of dispersing up to 100 million sterile flies per week.
- It continues to disperse 100 million sterile flies per week in Mexico, sourced from the COPEG facility in Panama. The USDA is providing support to Mexico to renovate a production facility in Metapa, which is expected to produce an additional 60-100 million sterile flies.
- It is conducting monthly audits of Mexico’s New World Screwworm response and is helping Mexico develop a more risk-based trapping plan, especially in Veracruz and along the border. Mexico currently deploys traps in high-risk areas, with the support of the USDA.
Currently, US ports remain closed to imports of cattle, bison, and horses from Mexico due to the threat of NWS.
First case of highly pathogenic avian influenza (HPAI) in Nebraska
On 15 September, the USDA confirmed the detection of highly pathogenic avian influenza H5N1 clade 2.3.4.4b, genotype B3.13 in a dairy cattle herd in Nebraska. This is the first known case of HPAI in cattle in Nebraska.
While dairy cattle in a total of 18 states have been infected since the start of the outbreak in March 2024, the Animal and Plant Health Inspection Service (APHIS) has seen cases in only a small number of states this year, the USDA stated.
The USDA highlights that biosecurity is still essential to mitigate the risk of disease introduction or spread between premises. The APHIS recommends enhanced biosecurity measures for all dairy farms, especially since the migratory bird season approaches in autumn. Any livestock with clinical signs, or any unusual sick or dead wildlife, should be reported to the state veterinarian.
The Nebraska Department of Agriculture (NDA) has issued an importation order stating that in an effort to protect the dairy herd in Nebraska, it is issuing an importation order that will require all breeding female dairy cattle entering the state of Nebraska to obtain a permit issued by NDA prior to entry. The order has been extended to 30 November 2025 and will be re-evaluated on a quarterly basis.
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