Screwworm Threat Looms Over U.S. Beef Supply Chain
A flesh-eating parasite is advancing through Mexico, threatening U.S. cattle imports and driving up beef prices.
The Situation
The New World Screwworm, a parasitic fly eradicated from the U.S. in the 1960s, is moving north from Central America into Mexico. This development has prompted the U.S. government to suspend cattle imports from Mexico—a country that supplies more than one million head of cattle to the U.S. annually.
With the U.S. cattle herd already at a multi-decade low, the disruption could significantly impact supply, elevating beef prices even further.
What Is the Screwworm?
Screwworms are flies whose larvae feed on the living tissue of warm-blooded animals. Females lay eggs in open wounds, including small abrasions, brands, or healing ear tags. Once hatched, larvae burrow into the flesh, enlarging the wound and, if left untreated, ultimately killing the host.
This pest was eradicated from the U.S. decades ago through a program that involved releasing sterilized males to interrupt reproduction. The current northward spread of screwworms poses a serious risk to both livestock and biosecurity.
Impact on Beef Supply and Prices
The import suspension cuts off a critical source of feeder cattle.
A reduced supply of cattle puts upward pressure on beef prices, which are already at record highs.
A previous screwworm-related import ban from November to February also contributed to price increases earlier this year.
Beef prices are expected to remain high throughout the summer, with retailers and consumers already feeling the impact.
Containment Efforts
The U.S. Department of Agriculture is responding by converting a fruit fly facility in Mexico to produce sterile screwworms, allocating $21 million to the effort. The goal is to flood the environment with sterile males to suppress the outbreak.
Meanwhile, a factory in Panama is currently releasing 100 million sterile screwworm flies each week. Experts say this effort must be scaled rapidly to prevent further northward movement.
Risks to U.S. Ranchers
If screwworms cross into the U.S., the Texas economy alone could face up to $1.8 billion in losses from livestock deaths, labor, and treatment costs. Most ranchers today are unequipped to identify or treat screwworm infestations, as the pest has not been present for decades.
Treating infections requires the manual removal of larvae and intensive wound care—laborious, expensive, and disruptive to herd health and operations.
Conclusion
The screwworm threat adds a new layer of uncertainty to an already strained beef market. For producers, importers, and retailers, this is a critical development to watch. If not contained, the parasite could destabilize supply chains and further inflate meat prices in the months ahead.