Officials confirmed Wednesday that Arizona's first case of New World screwworm was found in a dog in Cochise County.
The Arizona Department of Agriculture, which is operating in close coordination with the U.S. Department of Agriculture, confirmed the case after the initial detection was reported Tuesday evening.
A veterinarian in Cochise County examined a canine suffering from a prominent back wound, officials said.
The practitioner observed that the lesion was heavily infested with aggressive fly maggots exhibiting classic biological markers of New World screwworm, according to an agriculture department news release.
Diagnostic specimens were harvested and dispatched to the Animal and Plant Health Inspection Service’s National Veterinary Services Laboratories in Ames, Iowa, where testing confirmed the presence of the invasive parasite.
This confirmation marks a high-stakes biosecurity event for the American Southwest.
Eradicated from the United States decades ago, New World screwworm has historically maintained a presence in South America before pushing steadily northward through Central America and Mexico.
Following confirmed domestic detections in Texas and New Mexico in June 2026, the arrival of New World screwworm in Cochise County places the parasite directly adjacent to major international border crossings — such as the Sonora-Chihuahua border region near Agua Prieta — and vital interstate livestock transport corridors along Interstate 10.
Given the Southwest’s extensive beef and dairy production systems, an unchecked outbreak poses a catastrophic economic threat to the region’s multi-billion-dollar agricultural sector.
The Associated Press reported that Mexican cattle began moving on Monday through a border crossing in New Mexico that had been closed for nearly two years as both nations work to stop the flesh-eating New World screwworm from spreading.
The screwworm has threatened the $113 billion U.S. cattle industry.
Containment efforts have cost jobs and trade in border communities, cutting off a source of cattle as the U.S. struggles to rebuild drought-depleted herds. Reopening crossings could help ease that squeeze, although experts caution that shoppers shouldn’t expect quick relief on beef prices.
The port at Columbus, New Mexico, is the third to resume Mexican cattle imports under new safeguards, which include tests, shots and inspections that happen before an animal even gets close to the border.
If conditions for safe trade are in place, cattle imports will resume in Nogales, Arizona, on Nov. 30.
