Screwworms Return: Texas Takes Action to Protect Livestock

Texas Takes Action Against Reemerging Parasitic Fly Threat

Texas is actively working to prevent the reemergence of a parasitic fly that could have significant consequences for the state’s agricultural sector. The Texas Department of Agriculture (TDA) is leading an initiative to stop the spread of the "new world screwworm," as stated by Commissioner Sid Miller in a press release on July 21. This effort involves introducing a synthetic bait known as Swormlure-5, designed to attract and eliminate the pests.

The new world screwworm was recently identified in Mexico, prompting coordinated efforts between Texas and the U.S. Department of Agriculture to eradicate the pest. Miller emphasized the broader implications of this issue, stating that it is not just a local concern but a nationwide crisis. He warned that the pest could lead to billions of dollars in economic losses and place a heavy burden on agriculture, wildlife, and public health systems.

"We cannot wait for sterile flies alone to turn the tide. That's why we're applying a little cowboy logic and bringing back swormlure, now with an enhanced formula that's more powerful and effective than ever," Miller said.

Understanding Screwworms

Native to the Western hemisphere, the new world screwworm is a parasitic fly that lays eggs in the fresh wounds of warm-blooded animals. According to Texas A&M AgriLife Extension, the larvae or maggots feed on the animal’s flesh, causing severe wounds and potentially death if left untreated.

The name "screwworm" comes from the feeding behavior of the maggots, which burrow or screw into an animal's wound. As they feed using their sharp mouth hooks, they cause extensive damage to the host's tissue. Over time, this can lead to severe wounds and "deadly damage" to the animal if not discovered or treated.

Signs of Screwworm Infestation

Some indicators of a screwworm infestation include:

• Foul-smelling wounds with visible maggots
• Animals biting or licking at wounds
• Lesions in navels, ears, dehorning or branding sites
• Unusual restlessness or lethargy

Although screwworms were eradicated in the U.S. in the 1960s, they have occasionally reemerged over the years.

Texas’ Strategy to Combat Screwworms

Previously, Texas used a synthetic bait called "swormlure" along with a mix of the insecticide dichlorvos to control the pests. Now, the state is employing a newer version of the bait, Swormlure-5, which acts as an attractant and capture tool. According to the TDA, Swormlure-5 targets only screwworms and blow flies, posing no threat to honeybees, monarch butterflies, or other pollinators.

Miller noted that in prior research and deployment, this method eliminated approximately 90% of the flies within a two-to-four-week period. The remaining 10% were then eliminated through the release of sterile male flies in areas where traps were deployed.

The TDA stated that these efforts will reinforce existing sterile fly operations and "supercharge" early detection and suppression of screwworms, helping to protect livestock and wildlife.

Collaborative Efforts

In addition to its own initiatives, the TDA is collaborating with the U.S. Department of Agriculture and the Mexican Government to monitor and control potential screwworm hotspots. Miller emphasized the importance of a united effort, saying, "We've beaten the NWS before, and we'll do it again. But it will take all hands on deck."

He expressed confidence in the effectiveness of Swormlure-5, calling it a potential game-changer in the fight against the new world screwworm. "We need another success story like we had in the '70s, and I believe Swormlure-5 bait is the game-changer that will get us there," he concluded.