Flesh-Eating Screwworm Returns to U.S. Cattle After 60 Years, Sparking Agricultural Crisis

For the first time in six decades, a devastating agricultural parasite has breached the United States border, threatening the multi-billion dollar cattle industry. The New World screwworm—a flesh-eating fly larva that burrows into the living tissue of warm-blooded animals—has established a foothold in the American Southwest.[2]

As of late June 2026, federal and state agricultural authorities have confirmed at least 16 animal infections across Texas and New Mexico. The victims so far include cattle, sheep, goats, and one domestic dog, signaling that the outbreak has already spread beyond the initial contamination zones in southern Texas.[2][4][5]

The biological reality of the New World screwworm (Cochliomyia hominivorax) is gruesome. Female blowflies deposit hundreds of eggs on the edges of open wounds—even minor ones like tick bites or umbilical scars on newborn calves. Once hatched, the maggots use sharp mouth hooks to tear into living flesh, burrowing deeper as they feed. Left untreated, an infestation can kill a mature animal within a week.

The parasite's return marks the reversal of one of the most successful pest eradication campaigns in American history. Through the aggressive release of sterile male flies, the U.S. Department of Agriculture (USDA) officially eliminated the screwworm from the continental United States in 1966. For decades, a joint U.S.-Mexico commission maintained a biological barrier, eventually pushing the pest as far south as Panama.

But that barrier has collapsed. Since 2023, outbreaks have surged northward through Central America and Mexico. Experts attribute the resurgence to a combination of climate change expanding the fly's viable habitat, increased movement of cattle across borders, and disruptions to sterile fly production during the pandemic.[4]

The first domestic case of the current crisis was detected on June 3 in a three-week-old calf in Zavala County, Texas. Since then, the parasite has jumped hundreds of miles, with cases appearing in West Texas counties and across the state line in New Mexico. The rapid geographic jump has alarmed veterinarians, who fear the true scale of the outbreak may be larger than the confirmed case count suggests.[2][3][4]

The economic stakes are massive. Texas is the nation's largest beef producer, and the outbreak arrives at a time when beef prices are already at near-record highs. International markets are reacting swiftly; on June 5, Canada instituted a ban on imported cattle that had been in Texas within the previous 21 days, threatening a lucrative export channel.[2][5]

The primary weapon against the screwworm remains the Sterile Insect Technique (SIT). Because female screwworms mate only once in their lifetime, flooding an environment with sterile males ensures that wild females lay unfertilized eggs, eventually crashing the population.

However, the U.S. is facing a severe supply shortage. The sole facility producing sterile flies, located in Panama, has ramped up production to roughly 115 million flies per week. Agricultural experts project that eradicating the pest from North America will require between 500 million and 700 million sterile flies weekly. A new Texas-based breeding facility is being accelerated, but it will not come online until next year.[3][5]

In response, USDA Secretary Brooke Rollins has secured $1.3 billion in emergency federal funding to tackle the crisis. The agency has also launched a $105 million "Grand Challenge," funding 40 research projects to develop next-generation eradication tools. These include breeding sterile males with hyper-active sex drives, deploying AI-controlled drones to monitor wildlife, and using trained dogs to sniff out larvae.[5][6]

Despite the influx of funding, the federal response has become a flashpoint for political friction. Secretary Rollins has publicly pointed to the previous administration's border policies and funding cuts as the catalyst for the parasite's northward march. Supporters argue the current USDA was proactive, catching the threat early and mobilizing unprecedented resources before the first domestic case even occurred.[1][3]

Critics and local officials, however, accuse the USDA of downplaying the immediate danger to ranchers. Some agricultural leaders are demanding a formal emergency declaration, which they argue would unlock further federal resources and provide clearer compensation protocols for ranchers whose herds are quarantined. The USDA maintains it already has the necessary authority to manage the crisis without a formal declaration.[3]

Amid the agricultural panic, public health officials are urging calm regarding human safety. While the screwworm can occasionally infect humans, such cases are exceedingly rare. The Centers for Disease Control and Prevention (CDC) states that the current risk to the U.S. public is very low, with no locally acquired human cases reported during this outbreak.[4]

Furthermore, the USDA has assured consumers that the U.S. food supply remains safe. The screwworm does not infest meat, and strict inspection standards prevent any contaminated livestock from entering the commercial food chain.[2]

For now, ranchers across the Southwest are on high alert, inspecting their herds daily for unusual wounds or signs of distress. With the sterile fly supply bottlenecked and the summer heat providing ideal breeding conditions, the battle to push the flesh-eating parasite back out of the United States is expected to be a grueling, multi-year campaign.[3][5]