The USDA’s Animal and Plant Health Inspection Service (APHIS) released an updated New World screwworm (NWS) Response Playbook this week to serve as a comprehensive guide for coordinated, science-based action should the parasitic insect reach U.S. territory.

The USDA called NWS a “devastating pest” that can cause serious, and in some cases, deadly infestation to animals and humans.

NWS continues to persist in parts of South America and has recently moved north through Central America and Mexico. It reached southern Mexico in late 2024, prompting an initial closure of the U.S. border to livestock imports. After a brief reopening, the border has been closed continuously since May 2025, removing more than 1 million head of Mexican cattle a year from the U.S. market at a time when the U.S. beef herd is at a 75-year low and beefpackers are struggling with severe cattle shortages.

The scourge was eradicated decades ago from the United States, which remains NWS-free. Nevertheless, agricultural authorities continue to work to keep NWS from crossing the Rio Grande, and to prepare in the event it does.

USDA is executing its five-pronged plan to keep NWS out of the United States, Under Secretary for Marketing and Regulatory Programs Dudley Hoskins said.

“While we are aggressively safeguarding American agriculture and working with Mexico to prevent further northward spread, we must also ensure that our domestic response plans are ready for immediate activation,” he said. “Strong coordination with states, producers, veterinarians, sportsmen and other partners is essential to achieving that goal.”

The updated Playbook outlines critical science-based strategies for federal, state, tribal and local responders, including how to coordinate responses, reduce the spread of NWS, manage infested animals and maintain business continuity.

In October, APHIS shared a draft Playbook in order to gather feedback from a spectrum of stakeholders, such as state animal health officials, federal and tribal partners, livestock and wildlife industry groups, veterinary organizations and others.

According to APHIS, the updated Playbook reflects the respondents’ expertise and operational experience and provides field-ready guidance for real-world response scenarios. To ensure continued alignment with state-level plans and industry practices, APHIS has pledged to revise the Playbook as preparedness activities advance and evolve.

The NWS Foreign Animal Disease Preparedness and Response website is www.aphis.usda.gov/animal-emergencies/nws.

For more information about USDA’s efforts to prevent and prepare for NWS, visit Screwworm.gov.