Sign up for TPR Today, Texas Public Radio's newsletter that brings our top stories to your inbox each morning.
The United States is expanding its efforts to combat the ongoing spread of the New World screwworm (NWS) into Texas, this time using a combination of sterile flies with fluorescent dye.
The harmful parasite continues to inch over to the Texas-Mexico border, with the northernmost active case around 200 miles from the border. Experts and officials say the flesh-eating parasite poses a threat to the livestock industry, pets, and people.
The USDA currently produces more than 100 million sterile flies per week in a facility in Panama and disperses them across Mexico.
The USDA’s Animal and Plant Inspection Service (APHIS) announced late last month it would shift its efforts to refocus its coverage along the U.S-Mexico border. This includes 50 miles into Texas, along the border with the Mexican state of Tamaulipas.
“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,” Dudley Hoskins, Under Secretary of Marketing and Regulatory Programs for USDA, said in a news release. “We are shifting our polygon as we make every effort to prevent NWS from reaching our border.”
The USDA said sterile insect dispersal — when paired with other techniques such as surveillance, movement restrictions, and outreach — is an effective tool in eradicating NWS.
Female screwworm flies will only mate once during their lifetimes. If they mate with sterile male flies, it will result in unfertilized eggs that don’t hatch. Releasing sterile flies outside of affected areas ensures that the screwworm flies that travel to a new area will not be capable of reproducing.
“Think of it as insect birth control,” said Dr. Casey Locklear, a Texas-based veterinarian and parasiticide lead at Elanco Animal Health. “When a male sterile fly mates with a female fly, she is unable to lay eggs (which) effectively breaks the life cycle.”
Although NWS cases have so far only been reported in animals across Mexico, releasing sterile flies north of current active sites will provide a buffer zone for flies that begin to move closer to the border.
In order to ensure Texas officials, veterinarians, and ranchers can differentiate between sterile and wild screwworm flies, the USDA will dye the sterile pupae.
That fluorescent dye will transfer to the sterile flies once they hatch and will glow under a UV light and could potentially be visible to the naked eye.
“This glow-in-the-dark aspect is a really neat and easy way for scientists to distinguish a safe fly that’s part of our proactive measures versus a potential threatening fly that’s made its way into a new area,” said Locklear.
Texas Gov. Greg Abbott recently issued a disaster declaration on NWS. The preemptive declaration directs the Texas Parks and Wildlife Department and the Texas Animal Health Commission to establish a joint Texas New World Screwworm Response Team.
The USDA also announced this week it had completed a sterile fly dispersal facility in Edinburg to combat the spread of the screwworm and will build a sterile fly production facility in Texas at a later date.
Locklear said the ongoing vigilance on the spread of the screwworm is crucial not only for livestock producers, but to pet owners as well.
“Remain vigilant as the threat of New World screwworm rises, watch your pet for any signs of non-healing wounds, any unexpected wounds … because those are areas of opportunity for New World screwworm.”
