By Julie Tomascik
Editor

Federal and state officials are intensifying efforts to prevent the re-emergence of the New World screwworm (NWS) in the United States by shifting resources closes to the Texas-Mexico border as the pest continues to move north in Mexico.

The U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) announced its reallocating sterile fly dispersal operations to reinforce coverage along the U.S.-Mexico border.

The new dispersal area will include operations along the border with Tamaulipas, Mexico, extending roughly 50 miles into Texas.

USDA produces and disperses about 100 million sterile flies each week as part of its primary strategy to stop the spread of NWS. Sterile fly releases are designed to create a buffer zone that prevents reproduction if the fly continues its northward movement.

“At Secretary Rollins’ direction, our highest priority is protecting the United States from screwworm,” said Dudley Hoskins, Undersecretary of Marketing and Regulatory Programs for USDA. “The northernmost active case of NWS in Mexico is still about 200 miles away from the border, but we’ve seen cases continue to spread in Tamaulipas and further south in Mexico. So, we are proactively shifting our polygon as we make every effort to prevent NWS from reaching our border.”

The sterile insect technique works by releasing sterile male flies, which mate with wild females that only reproduce once in their lifetime. When females mate with sterile males, the eggs laid do not hatch, slowing the population’s spread.

USDA officials noted sterile flies may be detected in Texas traps as part of this proactive strategy. To differentiate sterile flies from wild ones, released insects are marked with a fluorescent dye visible under ultraviolet light.

In addition to sterile fly dispersal, USDA continues to enforce import restrictions, wildlife inspections and surveillance and trapping efforts.

To date, more than 42,000 flies collected from border-region traps have been tested with no detections of NWS inside the U.S., according to USDA.

Wildlife inspections of more than 9,300 animals across 131 U.S. counties, USDA said, have also shown no signs of infestation.

At the state level, Gov. Greg Abbott issued a disaster declaration in January in response to the growing threat, allowing Texas agencies to mobilize resources and coordinate prevention and response efforts.

The coordinated approach between federal and state agencies is critical to protecting livestock, wildlife and rural economies.

“USDA’s decision to shift sterile fly dispersal to the border, combined with the governor’s disaster declaration, strengthens the protective barrier Texas agriculture depends on,” said Tracy Tomascik, Texas Farm Bureau associate director of Commodity and Regulatory Activities.

Although the northernmost active NWS case in Mexico is about 200 miles away, Texas farmers and ranchers are urged to remain vigilant and report any suspicious wounds or infestations immediately.

“Early detection and reporting are essential,” he said. “Farmers, ranchers and animal owners are the front line in this effort, and their vigilance is important in protecting Texas and the nation from this devastating pest.”

Adult screwworm flies are about the size of a common housefly or slightly larger, with a metallic green or blue body, orange eyes and three dark stripes down its back.

NWS maggots can infest livestock and other warm-blooded animals, including people. They most often enter an animal through an open wound and feed on the animal’s living flesh.

Signs of NWS infestation include draining or enlarging wounds and signs of discomfort. Screwworm larvae (maggots) and eggs can be found in and around body opening, such as the nose, ears and genitalia or the navel or newborn animals.

Visit screwworm.gov to view a map with active NWS cases.