By Karen Gleason
The 830 Times
It sounds like the plot summary of a B-grade horror movie: A community is threatened by an invader who eats its victims alive as a group of earnest, hardworking men and women race the clock to stop it.
But this is no Hollywood fantasy, it’s the reality facing livestock producers and game ranch managers in Val Verde County as they brace themselves for a new war against an old foe: the New World Screwworm.
The New World Screwworm, a parasitic blowfly, lays its eggs in a warm-blooded animal’s wounds or scratches or in its thin mucous
membranes. When those eggs hatch, the larvae eat their way through the hapless victim’s living flesh. In the past, New World Screwworms devastated herds of livestock and wildlife populations alike before being eradicated from the U.S., Mexico and Central America by the herculean efforts of local, state and federal governments and their contractors.
The new threat facing local livestock producers was discussed Thursday during a two-hour-long emergency meeting of Val Verde County Commissioners Court, called by County Judge Lewis G. Owens Jr. and attended by about 45 area ranch owners and managers.
To accommodate the larger-than-normal crowd, Owens moved the meeting from the old county court-at-law courtroom off East Losoya Street, where the court normally meets, to the second-floor county court-at-law courtroom in the main courthouse off Pecan Street.
Owens opened the meeting with the “Citizen Comments” portion of the agenda, recognizing former Del Rio City Councilman and livestock producer Lee Weathersbee.
Weathersbee, who said he’d grown up in a ranching family, held up a pair of slim stainless-steel forceps that he said he’d used as a young man to pull the screwworm fly’s flesh-eating larvae from the open sores on livestock.
“I was just a teen in the mid ’50s when I faced this rascal, and when I heard about it (coming back), the nightmares and the horrors it brought back was just unbelievable. We had no deer. They couldn’t raise a fawn. (The flies) would come to the blood, and the worst part about it all, human beings weren’t safe from it, and there were some people in San Antonio that died of it.” Weathersbee said.
After Weathersbee spoke, Owens said he’d begun getting phone calls about the screwworm situation on Saturday, adding he learned there had been a confirmed case in Musquiz, Coah., Mexico, about 70 miles from the Texas border.
Owens then called on Tommy Yeater, Val Verde County agent for agriculture and natural resources, who thanked everyone for coming and
said, “It is a very crucial time for us. I appreciate the Texas Animal Health Commission for working with us to get here on such short notice.”
Yeater introduced Dr. T.R. Lansford, deputy executive director of the Texas Animal Health Commission, and Dr. Sandra Leyendecker, Laredo region director for the Texas Animal Health Commission.
Yeater said, “This is not gloom and doom as it was back in the ’60s and ’70s. I do remember as a child, digging those maggots out and throwing some black goop in (the wound) that stunk to high heaven. We’ve come a long way from that. . . The main thing I’d like to push to you all as our producers in Val Verde County is please report any cases. That’s the main thing. The fastest way this spreads is by somebody not reporting it and putting an animal in a trailer and hauling it across the state.”
He added, “We’ve had several cases in Mexico before the case in Musquiz, but this group (Texas Animal Health Commission) and the USDA have kept it from coming into Texas on numerous occasions already, but it’s still moving north, but it ain’t stepped over into Texas yet.”
Yeater turned the mic over to Leyendecker, who began an in-depth presentation on the New World Screwworm, also called NWS.
Leyendecker began her presentation with photos of the NWS, which, except for a few physical details, looks much like an ordinary housefly.
“The key thing is that the NWS maggots infest living tissue. They’re not like the maggots you’d find on a dead animal. These, literally, the fly looks for a wound, lays her eggs and the maggots that result are eating live flesh,” Leyendecker said.
Throughout her presentation, Leyendecker implored those attending to call her if they discover an animal with NWS maggots on it.
She said humans moving livestock to and from their ranches are more responsible for the fly’s expansion in range than the fly would be by itself.
“Back in the day, it took 34 years to eradicate screwworms from North America down past Central America and into Colombia,” she said.
Leyendecker said a facility in Panama is the only remaining producer of sterile screwworm flies, which were used to eradicate the screwworm fly in the U.S., Mexico and Central America. She said Mexico is building a sterile fly production facility in the state of Chiapas, and an old airfield in Mission, Texas, will once again serve as the focal point for eradication efforts in the U.S.
Leyendecker said after the screwworm had been effectively eradicated from the U.S., Mexico and Central America in the last century, an increase in cases was noted in Panama in 2022.
“In July of 2023, they saw them in Costa Rica, and then in September (2023), Honduras, and we as an agency started to worry in September 2024. . . In two years, (NWS has spread) from Panama to Chiapas, Mexico,” she said.
Leyendecker also told the group that the most recent confirmed case was found Tuesday in Zaragoza, Coah., Mexico, 28 miles from Eagle Pass.
Animal Health Commission, gives a presentation about the New World Screwworm to members
of county commissioners court and a group of local ranchers during an emergency meeting of the
court on Thursday. (Photo by Karen Gleason)
“As long as there are screwworms in Mexico, we are at risk,” she said.
Leyendecker said any warm-blooded animal, including wildlife like whitetail deer, javelina, rabbits, foxes and squirrels, domestic animals like horses, cows, sheep, goats, dogs and cats and humans, as well as birds, can be infected by NWS.
Leyendecker also went over the NWS life cycle. After the female fly mates, she will look for a warm-blooded animal with a wound. Leyendecker said the wound can be small, for instance, a scratch from a barbed wire fence or a wound caused by dehorning or ear-tagging, and the fly will lay her eggs in that wound.
The eggs hatch within 12 hours. The fly larvae – maggots – begin feeding on the living tissue of the host animal, and in a week, they will drop off the animal. They will burrow into the ground to form a pupa, and from that pupa a new fly will hatch to begin the life cycle anew.
Leyendecker said adult NWS flies have bright red or orange eyes, three dark lines on the back of their thoraxes (the upper body of the insect) and are a metallic blue or green. The veterinarian warned, however, that many flies can have the same color characteristics.
She said until the National Veterinary Sciences Lab in Ames, Iowa, confirms the presence of an NWS, the USDA will not drop sterile flies in the area.
Leyendecker also spoke about how sterilized flies are dispersed, with the two major methods being dropping chilled sterile flies from aircraft and releasing them from ground dispersal units. She said dispersal of sterile flies is concentrated in areas where NWS has been confirmed.
In the late 1970s and early 1980s, Del Rio International Airport served as the home base of the Del Rio Flying Service, a locally-owned company that operated under contract with the USDA to drop sterile flies in the region and at the time, boasted the largest fleet of single-engine aircraft in the United States.
Leyendecker said the TAHC is also carrying out surveillance trapping in the region to learn how the NWS are moving and where the next outbreak might occur.
“We can’t protect you if we don’t know where it’s at,” Leyendecker said.
Leyendecker spoke about some signs to look for in infected animals and showed a series of graphic photos of NWS infestations on a variety
of domestic animals and on humans.
She urged ranch managers to regularly check their animals for wounds and spoke about other preventive and treatment methods.
When Leyendecker finished, Owens asked her to email him the presentation so it could be posted on the county’s website.
Lansford also spoke to the group, stressing the importance of movement controls and inspections, reviewing treatments and surveillance.
Lansford stressed, “This is not a food safety issue.”
He, too, urged those attending the meeting to quickly report any possible infestation so steps can be taken to quickly respond and prevent the flies from spreading farther into the U.S.
Following the presentations, Lansford and Leyendecker fielded questions from some of those attending the meeting.
The writer can be reached at delriomagnoliafan@gmail.com
depicting the successful efforts to eradicate the New World Screwworm from North America. Efforts in the latter half of the 20 th Century pushed the parasitic fly south of the Darien Gap in Panama, but in the past three years, NWS cases have been reported in Central America and Mexico. In the past week, a case was confirmed in Zaragoza, Coah., Mexico, 17 miles from Eagle Pass, Texas. (Courtesy graphic/Texas Animal Health Commission)
