The New World Screwworm (Cochliomyia hominivorax), a parasitic fly once eradicated from North and Central America through decades of coordinated effort by governments and livestock producers, is making a troubling return—this time through a backdoor few anticipated: narco-funded cattle ranching. In parts of Central America, illegal ranching on protected lands has become a front for drug trafficking and money laundering. The ripple effects of this trend now threaten U.S. cattle producers with the resurgence of a deadly livestock pest.
The Screwworm Fly
The screwworm fly is incredibly damaging to livestock operations. It lays its eggs in even the smallest wounds where they grow into screw-shaped larvae that eat their hosts alive. If left untreated, a screwworm infestation can kill a cow in 7 to 14 days. The cost to producers of monitoring for the fly, treating animals, and losing animals to the fly was enormous. In the 1950s, screwworm infections cost American ranchers up to $200 million per year, equivalent to nearly $1.8 billion in today’s dollars.
So you can imagine everyone’s excitement when scientists discovered they could eradicate the fly with the “Sterilized Insect Technique” (SIT). Raymond Bushland and Edward F. Knipling discovered that the female screwworm fly only mates with one male, while the male tries to mate with as many females as possible. The two scientists developed a technique of sterilizing male flies and releasing them in the wild to reduce the number of eggs and larvae. Ranchers worked closely with scientists, their local veterinarians, and government agencies to identify infestations, treat them, and release sterilized male flies in their region. Over time, the fly was eradicated from the U.S., then Mexico, then all of the neighboring countries in Central America, down to Panama.
Since 2006, the U.S. and Panama together have maintained a barrier zone of sterile male flies to prevent wild screwworm flies from South America from reinfesting Central and North America. At the same time, USAID staff helped maintain the barrier by working with local ranchers and veterinarians in Mexico and Central America. Their job was to monitor for the screwworm and ensure that outbreaks were treated immediately to prevent further spread of the flies.
But the barrier is beginning to break now. According to USDA’s Animal and Plant Health Inspection Service (APHIS), “In 2023, NWS detections in Panama exploded from an average of 25 cases per year to more than 6,500 cases in 1 year. Since then, screwworm has been detected in Costa Rica, Nicaragua, Honduras, Guatemala, Belize, El Salvador, and Mexico, north of the biological barrier that’s successfully contained this pest to South America for decades.” Understanding the reasons why this is happening is critical to finding another long-term solution.
Cattle, Cocaine, and Conservation Zones
At the heart of this issue is the rise of “narco-ranching.” Drug traffickers in countries like Honduras, Guatemala, and Nicaragua purchase land, or more often move into biosphere reserves, clear forests, and run cattle herds to launder profits from the drug trade. These cattle are smuggled northward through Mexico, bypassing health inspections and veterinary oversight.
Insight Crime’s fourteen-month-long investigation found that the illegal cattle market is a convenient way for drug traffickers to move their product north to the United States, which continues to be the world’s largest consumer of cocaine. It’s also an excellent way to launder money and diversify their income sources by controlling land and timber resources that they can sell for additional income.
The illegal cattle trade is also fueled by Mexico’s domestic demand for beef and the growing global market as well. This creates an incentive for ranchers—legal and illegal alike—to scale up operations, even at the cost of forest loss and disease risk. Narco-ranchers can easily sell their cattle into this growing market, blending them with legitimate stock and bypassing the biosecurity checks that were key to screwworm eradication decades ago. The New World Screwworm thrives in these unsupervised conditions.
U.S. Funding Cuts and the Breakdown of Preventive Systems
The United States once played a central role in preventing problems like this. Through USAID and the USDA, it partnered with Central American governments on eradication programs, border inspections, and sustainable rural development.
But with the start of the Trump administration, funding cuts have undermined these systems:
- USAID anti-drug programs in Colombia and Peru have been suspended or reduced, withdrawing support for legal rural industries and crop substitution. (AP News)
- In Colombia, over 80 programs connected to peacebuilding and anti-coca strategies were shut down in early 2025. (Reuters)
- Funding and coordination around veterinary inspection and vector control—key to screwworm surveillance—have also dwindled, leaving gaps at exactly the time smuggling is expanding.
These funding cuts have eroded local alternatives to illicit economies, strengthened criminal control of remote territories, and opened new routes for screwworm resurgence.
Implications for U.S. Ranchers and the USDA’s responses
Today, Texas and other border states remain at risk from reinfestation, particularly if infected animals cross undetected. Wildlife—especially white-tailed deer, feral hogs, and stray dogs—could serve as hidden hosts, complicating containment. And as seen in a recent case in Chiapas, Mexico, authorities can be slow to detect outbreaks until the flies have already spread. (Reuters)
The Chiapas outbreak caused the U.S. to suspend live cattle imports from Mexico on November 22, 2024. USDA Secretary Rollins lifted that suspension on February 1, 2025 after implementing new inspection protocols. The U.S. also coordinated with Mexico to begin aerial drops of sterilized male flies in outbreak areas and areas of concern. On May 11, Rollins reinstated the suspension. The suspensions are subject to monthly reviews, with the USDA emphasizing the importance of containment and eradication efforts in Mexico to ensure the safety of U.S. livestock.
Here’s what it could mean for the U.S. Cattle Industry and consumers:
Supply Chain Disruptions: Mexico has historically been a substantial supplier of feeder cattle to the U.S., Mexico has historically been a substantial supplier of feeder cattle to the U.S., with annual imports averaging over 1 million head. The sudden halt in imports disrupts feedlot operations, particularly in border states like Texas and Arizona, where producers rely on a steady influx of Mexican cattle to maintain production levels. This disruption forces feedlot operators to seek alternative sources, often at higher costs.
Increased Operational Costs: With the suspension in place, feedlot operators must procure cattle from domestic sources, which may be limited due to existing herd sizes and regional availability. This scarcity can drive up the prices of feeder cattle, increasing operational costs for producers. Brownfield Ag News
Rising Consumer Prices: The U.S. is reliant on Mexican cattle imports to meet domestic demand. In 2024 alone, the U.S. imported over 2 million head of cattle—approximately 1.25 million of which came from Mexico, USDA data shows. The combination of disrupted supply chains and increased operational costs contributes to rising beef prices for consumers. Analysts predict that if the suspension continues, consumers could see noticeable price hikes at grocery stores and restaurants by summer 2025. Parriva
2. Compounding Factors: The suspension exacerbates existing challenges in the beef industry, such as declining cattle inventories and increased production costs. For instance, Tyson Foods reported a $258 million loss in the second quarter of 2025, attributing part of the loss to reduced cattle supplies and increased costs. Straight Arrow News
3. Market Volatility: The uncertainty surrounding the duration of the import suspension contributes to market volatility, affecting futures prices and planning for producers and retailers alike.
A Policy Link Often Ignored
This is not simply a story of pests or parasites—it is a case study in how interconnected drug policy, rural development, and environmental security really are.
By cutting U.S. support for forest protection, Indigenous land rights, and alternative economies in Latin America, we’ve created conditions where narco-networks flourish—and the tools to fight old enemies like screwworm have been quietly dismantled.
The reemergence of the New World Screwworm isn’t just a veterinary concern—it’s a warning. As forest ecosystems collapse, Indigenous communities are displaced, and cattle laundering spreads unchecked, U.S. ranchers and farmers are left vulnerable to a preventable threat.
Reinvesting in international partnerships, sustainable development, and biosecurity programs isn’t charity—it’s strategic self-preservation.
Further Reading and Sources:
- The Secrets of Cattle Smuggling from Guatemala to Veracruz, Mexico
- Illegal Cattle Trafficking Is Fueling Dangerous Resurgence of New World Screwworm – Wildlife Conservation Society (notes that Mexican cattle producers are calling for immediate action to stop illegal cattle crossings.
- USAID cuts threaten Amazon forest and fuel drug trade concerns – Context News
- Mexico says US suspension of beef imports because of screwworm is unfair – Associated Press
- US halts Mexican cattle imports after screwworm found in Chiapas – Mexico News Daily
- U.S. halts live cattle, horse, bison imports from Mexico over screwworm outbreak – Laredo Morning Times
- Opportunities for Intervention in the Illegal Cattle Trade – See Chapter 6 of the Insight Crime full report.
