Flesh-eating screwworm has reached the US — a comeback driven by organized crime

The Flesh-Eating Screwworm Has Arrived in the U.S. Cattle Industry

Flesh eating screwworm has reached the US – The flesh-eating screwworm has reached the U.S., according to the U.S. Department of Agriculture, which confirmed the presence of New World screwworm in a Texas calf. This development has raised alarms among experts, as the parasite, known for its rapid reproduction and destructive feeding habits, marks a troubling return to American soil. Scientists have long warned about the risks of smuggling practices, which now appear to be the catalyst for this resurgence. The discovery underscores the growing threat posed by illegal livestock trade, as the fly’s spread could jeopardize millions of cattle and the multi-billion-dollar industry they sustain.

From Central America to the U.S. Border

Ecologist Jeremy Radachowsky, leading programs for the Wildlife Conservation Society, had predicted the screwworm’s reemergence. He emphasized the parasite’s ability to infest living hosts, a trait that makes it particularly dangerous. The last time the screwworm invaded the U.S. was in the 1970s, when it caused hundreds of millions in agricultural losses. This time, the threat is amplified by organized crime networks that exploit the cattle smuggling routes across Mexico and Central America. These groups, driven by economic incentives, have bypassed health inspections, allowing the fly to infiltrate new regions.

Radachowsky noted that the New World screwworm’s life cycle is both swift and relentless. Eggs laid in open wounds or body cavities hatch into larvae that consume the host’s tissue, often leading to fatal infections. The parasite’s survival strategy—relying on living animals for sustenance—means it can thrive in environments where livestock are moved without oversight. Recent smuggling activities in the Darien Gap, a critical corridor between Panama and Colombia, may have played a role in its northward expansion. As the screwworm has reached the U.S., its spread could complicate efforts to contain it within Mexico and Central America.

Environmental and Economic Fallout

The resurgence of the flesh-eating screwworm has reached beyond livestock, affecting ecosystems and local communities. Radachowsky highlighted the deforestation linked to illegal cattle ranching, which creates new habitats for the fly and destabilizes native wildlife. The parasite’s presence also threatens food security, as outbreaks could lead to mass culling of cattle herds. Meanwhile, the economic impact is projected to be severe, with estimates suggesting potential losses in the billions. The USDA’s decision to close southern border ports for livestock from Mexico in July 2025 was a direct response to this crisis.

“The spread of this parasite has reached a critical point,” said Radachowsky. “Every infected animal carries the risk of spreading the infestation further.”

Experts warn that the flesh-eating screwworm’s arrival in the U.S. could disrupt global trade networks. Smuggling operations not only introduce the fly but also facilitate the movement of other pathogens, such as avian flu and tuberculosis, through unregulated livestock transfers. This dual threat highlights the interconnectedness of environmental and public health challenges. The Mexican government has criticized the USDA’s border restrictions, arguing that they hinder agricultural partnerships and economic stability. However, the urgency of containing the screwworm’s spread has forced policymakers to prioritize immediate action over long-term trade considerations.

Authorities are now exploring multiple strategies to combat the infestation. The USDA and Mexico’s agriculture departments have resumed the use of sterilized flies, a method that proved effective in the past. This approach, which targets adult flies to prevent reproduction, is being combined with pesticide-based interventions like the Screwworm Adult Suppression System (SWASS). Radachowsky stressed that coordinated efforts across the U.S., Mexico, and Central America are essential to preventing a full-scale outbreak. While SWASS has been praised for its efficacy, concerns about carcinogenic chemicals have delayed its widespread deployment. The task force continues to evaluate its risks and benefits as the screwworm has reached the U.S. cattle industry.