New World Screwworms
New World Screwworms are re-emerging in Mexico at a rapid rate, threatening to cross back into Texas and other southern states with potentially devastating consequences for livestock and wildlife. Once eradicated through one of entomology’s greatest success stories, this flesh-eating parasite now faces weakened containment efforts that urgently need revitalization to protect our agricultural operations and ecosystem health.
Screwworms
Holding the line
New World Screwworm cases are surging from 25 to over 25,000 annually in Panama and spreading into Mexico; we face an urgent threat to North American livestock, wildlife, and human health. Our current defense, a single facility producing 100 million sterile flies weekly, is overwhelmed by this rapidly expanding outbreak. Agriculture Secretary Brooke Rollins’ commitment to establish a new U.S.-based production facility represents our determination to hold the line against this devastating parasite, providing the additional capacity needed to stop the screwworm’s advance and protect our agricultural and wildlife resources.
The Threat
New World Screwworms are devastating parasites whose larvae feed on the living tissue of any warm-blooded host, including livestock, wildlife, and humans. Adult flies lay eggs in open wounds or mucous membranes, and the feeding larvae cause a condition called myiasis. Affected animals attract more flies, creating a deadly cycle that can kill hosts within days if left untreated. This rapidly spreading outbreak threatens to reverse decades of successful eradication efforts across North America.
Our Defense Strategy
For over 20 years, the United States and Panama have collaborated on a joint international mission utilizing the sterile insect technique to protect North America from screwworm infestations. This biological barrier involves releasing millions of sterile male flies weekly to interrupt the pest’s reproductive cycle. The COPEG facility in Panama has successfully produced approximately 100 million sterile flies per week, creating a permanent barrier that has kept the continent screwworm-free since 2002.
Historical Success
The sterile fly program achieved remarkable success, completely eliminating screwworms from the United States by 1982, Mexico by 1991, and Central America by 2002. This technique even helped contain the 2015-16 outbreak affecting the endangered Florida Key Deer. However, this success led to the closure of other production facilities worldwide, leaving us vulnerable when the current crisis emerged. Historical eradication efforts required over 400 million flies per week—four times our current capacity—stressing the urgent need for expanded production capabilities.
International Cooperation
Screwworm eradication requires coordinated efforts across borders – this is a pressing issue since flies don’t remain within a specific boundary. Our partnership with Panama through COPEG shows how international collaboration can create effective biological barriers. Sharing resources, expertise, and prompt response capabilities ensures protection for the entire North American continent.
Prevention and Preparedness
While efforts to increase capacity for combating screwworms through both traditional and new technologies are encouraging, immediate action is still needed.
In the short term, we need guidance on the legal and ethical use of drugs for preventive treatment in cattle and wildlife. Clear direction on surveillance, reporting protocols, containment, and response measures is also essential. For this, we must rely on agency officials at the Texas Animal Health Commission and the Texas Parks & Wildlife Department. For education and outreach, the Texas A&M AgriLife network is critical. Additionally, we must stay engaged with USDA scientists and officials as they develop tools for control.
We may not be able to completely prevent screwworm infestations, but through preparation, we can mitigate their impact while developing the means to eradicate them once again. With luck, we might be able to avoid the worst.
Neal Wilkins, President & CEO
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