The United States faces a resurgence of the screwworm, a devastating flesh-eating parasite not seen domestically since the 1980s. Recent outbreaks in Texas and New Mexico signal the re-entry of *Cochliomyia hominivorax*, a fly whose larvae feed on living animal tissue. This marks a significant setback for decades of eradication efforts.

Prior to its elimination, screwworms caused catastrophic losses, killing millions of livestock and wildlife annually. The USDA's successful eradication program, starting in the 1930s, relied on the "sterile male technique." This method involves releasing millions of sterile male flies to mate with wild females, preventing viable offspring and ultimately eliminating the pest. A barrier at the Darien Gap maintained this success for decades.

However, the barrier at the Panama-Colombia border appears to have failed around 2023, allowing screwworms to spread north again. The USDA is now re-implementing eradication efforts, but expects the process to take years. The return of this parasite underscores how quickly a forgotten threat can re-emerge when control measures lapse.

The current outbreaks are a stark reminder of screwworm's destructive potential. Agricultural agencies are working to contain the spread, but the long road to eradication has begun anew.