Jessica Metcalf, a professor at Colorado State University, is leading research funded by the U.S. Department of Agriculture to develop improved lures for trapping the New World screwworm, a parasite that poses a threat to livestock and wildlife. The project focuses on identifying foul-smelling substances that attract the screwworm to open wounds, with the goal of enhancing detection and control efforts. The pest was eradicated in the United States over 50 years ago but was detected in Texas in early June.
Metcalf said her team is studying bacterial-produced smells from wounds—volatile organic compounds—to create lures specific to the New World screwworm. She explained, "We use these bacterial cues to stay away from certain things – to not eat spoiled meat, for example. The insects are using them for a different reason. They're like, 'Yes, bring it, that smells like a great place to lay eggs.'" Current traps often capture large numbers of secondary screwworms attracted by rotting meat odors, making it difficult to monitor for the more harmful species.
The USDA has allocated $105 million across 40 projects aimed at improving defenses against this parasite. As of July 23, cases have been found in cattle, sheep, goats, and dogs in Texas and New Mexico. Metcalf's team will analyze differences between volatile compounds produced by wounds versus those from dead flesh and identify bacteria unique to each blowfly species involved.
The research involves partnerships with CSU faculty members Kayla Borton and Kelly Wrighton through the Colorado State Microbiome Network, as well as outreach efforts coordinated by Tracey Goldstein of CSU's One Health Institute. Volunteers including livestock producers and veterinarians will help collect samples from animal wounds for laboratory analysis; stakeholders will receive diagnostic results and benefit from any solutions developed during the project.
Julia Herman of the National Cattlemen's Beef Association said producers must check animals for wounds before moving livestock: "We can't treat our way out of this problem," Herman said. "We have to have other ways to manage this fly... Hopefully we can take some of that stress off the producer and minimize time and resource loss with projects like Dr. Metcalf's."
Current international control methods rely on releasing sterile male blowflies bred at facilities operated by USDA and Panama’s Ministry of Agriculture Development—a technique effective for decades until recent reemergence in Mexico and Central America. Metcalf’s work may inform improvements such as assessing whether sterilization affects flies’ ability to attract mates or refining Sterile Insect Technique programs.
