FACT CHECK: Experts Debunk Claim That Screwworm Outbreak Is Solely Due to One Administration's Border Policy

The reemergence of the New World screwworm in the United States for the first time in nearly six decades has triggered a massive agricultural response—and a fierce political blame game. Since the first domestic case was confirmed in a South Texas calf in early June 2026, the outbreak has grown to over 30 animal cases across Texas and New Mexico.[3]

As the parasitic fly threatens the multibillion-dollar U.S. beef industry, some political figures have pointed to human migration and border enforcement as the primary culprits. U.S. Agriculture Secretary Brooke Rollins and several lawmakers have publicly argued that permissive border policies and the resulting illicit cattle trafficking allowed the pest to travel north from Central America.

However, entomologists, epidemiological investigators, and agricultural experts broadly reject this framing. An examination of the evidence reveals that the screwworm's spread is driven by biological factors, wildlife movement, and long-term shortages in sterile-fly production—not human migration policies.

One of the central political arguments suggests that a lack of border enforcement turned the Darien Gap into a highway for infested animals, causing the biological barrier in Panama to collapse. Entomologists point to a much different cause: a biological strain failure. The barrier, maintained since the 1990s by releasing sterile flies, began failing around 2022 because the wild screwworm population adapted, and aging production facilities simply could not breed enough sterile flies to keep up. Experts note this was a decades-in-the-making logistical failure, entirely unrelated to human border crossings.[1]

Another prominent claim is that illicit cattle trafficking across the U.S.-Mexico border brought the parasite directly to Texas ranches. The Texas Animal Health Commission has directly refuted this theory. Executive Director Lewis R. "Bud" Dinges recently testified to state lawmakers that epidemiological investigators have found absolutely zero evidence linking the Texas cases to the illicit movement of cattle from Mexico.

Instead, experts emphasize that the screwworm does not rely on human smugglers to cross international lines. Small, free-ranging wildlife—such as armadillos, rabbits, opossums, and deer—are highly efficient hosts. These animals move fluidly across the border through brush and desert, making traditional human-focused border enforcement ineffective at stopping the parasite's natural geographic expansion.[1]

The current administration has also claimed that the previous White House did nothing to prepare for or stop the outbreak, stating that no funds were secured before the transition of power. Federal records show this assertion is false. In late 2023, the USDA approved $109.8 million in emergency funding to combat the screwworm in Panama, followed by an additional $165 million in late 2024.

Furthermore, when Mexico reported its first case near the Guatemala border in November 2024, the USDA immediately halted imports of live cattle and bison from Mexico to protect domestic herds. Former directors of USDA emergency programs caution against reducing the outbreak to a simple partisan narrative, describing the situation as a long-term preparedness failure spanning multiple administrations and Congresses, exacerbated by international workforce shortages.[1]

With the political rhetoric set aside, the actual solution relies entirely on entomological science. The United States originally eradicated the screwworm in the 1960s using the Sterile Insect Technique, which involves releasing millions of sterile male flies to mate with wild females, resulting in unfertilized eggs and a collapsing population.[4]

To combat the current outbreak and push the parasite back south, the USDA estimates it needs up to 500 million sterile flies per week. To meet this immense demand, a newly retrofitted production facility recently opened in Metapa, Mexico, and a new $750 million facility is being constructed in Edinburg, Texas.[4]

In a major scientific breakthrough that could turn the tide of the outbreak, the USDA recently announced the development of the "Novo fly." This genetic advancement allows breeding facilities to produce 100 percent sterile males, instantly doubling the effective fighting force against the parasite without needing to expand physical plant capacity.

Meanwhile, public health officials are working to reassure the public that the risk to humans remains exceptionally low. While the screwworm can theoretically infest any warm-blooded animal, human cases are incredibly rare. The Centers for Disease Control and Prevention confirmed this month that there have been zero locally acquired human cases in the U.S. during this outbreak.[2]

The economic stakes of getting this scientific response right are massive. A widespread outbreak could cost the U.S. agricultural sector more than $700 million annually in direct losses and up to $2 billion in broader economic damage, driven by livestock mortality and restricted international trade. This underscores why agricultural economists are urging lawmakers to fully fund sterile-fly facilities rather than debating border wall funding as a solution to an insect problem.[4]

By focusing on entomological realities rather than political grievances, agricultural authorities are deploying the precise biological tools required to secure the U.S. livestock industry. The successful containment of the screwworm will depend on robust sterile-fly production and vigilant monitoring by ranchers, proving that scientific logistics, not border politics, will ultimately solve the crisis.[1][4]