New World screwworm threat continues as USDA, Texas tries to stop it

A parasitic fly that was eradicated from the United States in the 1960s has been slowly creeping back after being detected within 25 miles of the Texas-Mexico border, marking its closest approach to American soil to date.

U.S. Department of Agriculture Sec. Brooke Rollins said on a media call on Tuesday, June 2, that her department is actively working to prevent the New World screwworm from entering the U.S., but if it does, it is ready to combat it.

"The New World screwworm crisis farmers and ranchers experienced back then will not repeat itself today," Rollins said. "Unlike then, USDA is leading a robust, detailed and technologically advanced response."

As of June 2, no cases have been reported in the U.S., but the latest detection of the parasitic fly in Coahuila, Mexico, is causing concern and has reinforced the federal government's ongoing, multi-front response.

That response includes closing U.S.-Mexico livestock ports to the construction of a new $750 million sterile fly production facility at Moore Air Base in South Texas.

Here are the key takeaways, Sec. Rollins and other officials provided to the public during a media call on June 1.

What is the New World screwworm?

According to the USDA, the New World screwworm (NWS) is a parasitic fly that impacts livestock, pets, wildlife, and, less commonly, people and birds. Their larvae feed on the living tissue of warm-blooded animals.

USDA reports that the current risk to animals and people in the United States remains  very low and that NWS is not contagious.

Rather, Screwworm infestations begin when a female fly lays eggs on a wound or body opening. The eggs hatch intolarvae that burrow into the wound and feed on living tissue, then after about 7 days of feeding, larvae drop to theground, burrow into the soil, and pupate.

The adult screwworm fly emerges from the soil after 7 to 54 days.

Current cases of New World Screwworm in U.S., Texas

As Rollins stressed, there are no reported cases in the U.S.; however, there are cases reported in Mexico — one recently reported 25 miles from the U.S.-Mexico border.

"Last week, Mexico reported up to eight New World screwworm detections," Rollins said. "One detected 25 miles from the US-Mexico border with the goat in Coahuila, our closest detection to date."

The secretary reiterated that the development had not caught her department by surprise and that she had implemented a five-pronged plan last summer to detect, control and combat the NWS.

Rollins also took a moment to debunk recent headlines about the screwworm being detected one mile from the Texas border, which were propagated by Texas state Rep. Don McLaughlin, R-Uvalde, in a June 1 social media post.

"When that false information gets out, it causes significant panic, and rightly so, and especially if it's coming from elected officials and from media," Rollins said. "In an effort to get information out to be as transparent as possible, to make sure that everyone who's tracking this and who wants to track it has access to every single thing that we know."

New World screwworm activity, prevention in Texas

As Rollins put it, New World screwworm cases are being reported closer to the Texas portion of the U.S. Southern border than in New Mexico, Arizona and California.

Recently, the USDA, in partnership with the Department of War, constructed a new $750 million sterile fly production facility at Moore Air Base in South Texas.

"That facility will be capable of producing up to 300 million additional sterile flies per week, which is what we really need to begin pushing this back to South America," Rollins said.

Those flies are then released in certain areas to stop NWS from reproducing. The Texas investment comes on top of an additional $21 million investment to convert an existing facility in Metapa, Mexico, into an NWS sterile fly dispersal facility.

Texas Animal Health Commission Director Dr. Bud Dinges said TAHC staff is constantly monitoring traps for NWS detection and working with USDA to leverage and expand existing ground release sites for the distribution of sterile flies in South Texas.

Additionally, TAHC staff are increasing their presence in South Texas to bolster its NWS outreach programs and provide additional awareness and resources to locals.

Dinges also called upon all Texans to continue to monitor their animals closely and often for open wounds and infestations.

"Over 58,000 suspicious flies have been submitted for official identification, and none have been detected by New World as New World screwworms," Dinges said. "It remains possible that New World screwworms will never reach Texas. However, given the expanding New World screwworms and fly population in Mexico and the severe threat it poses to Texas livestock industry, livestock and wildlife industries, we now must prepare and act as if it will."

If individuals suspect an animal may be infested with New World screwworms. Notify the Texas Animal Health Commission or your local veterinarian immediately.

USDA has set up a new email address — [email protected] — where the public can submit questions about NWS. Individuals are also encouraged to visit screwworm.gov for more information and the latest updates on New World screwworms.

Mateo Rosiles is the Texas Connect reporter for USA TODAY and its regional papers in Texas. Got a news tip for him? Email him at [email protected].