The War on Screwworm: What the Return of a Flesh-Eating Parasite Means for Milam County Producers

CAMERON — For the first time in sixty years, Texas livestock producers are facing a familiar and devastating foe.

On June 3, the U.S. Department of Agriculture (USDA) and the Texas Animal Health Commission (TAHC) confirmed the state’s first case of New World Screwworm (NWS) since 1966, discovered in a three-week-old calf in South Texas. Within days, four more cases were confirmed across Texas and neighboring New Mexico, prompting Governor Greg Abbott to escalate Texas's emergency response operations to Level II (Escalated Response) and issue a rallying cry to the state's agricultural community.

“I have activated the full use of all state resources to respond to the New World Screwworm threat,” Governor Abbott said in an official statement. “The protection of our ranchers, livestock producers, deer breeders, and the Texas economy from this pest is a top priority. We have eradicated this pest before, and we will do it again in close cooperation with our federal partners. Texans should stay alert, check animals daily for wounds, and report any suspected cases immediately.”

While the initial cases are currently concentrated in South and West Texas—including a recent goat infestation in Gillespie County just west of Austin—ag leaders warn that Milam County ranchers and pet owners must immediately enter a state of high vigilance. If the fly establishes a foothold in the state’s dominant cattle-producing regions, the USDA estimates economic losses could skyrocket to $1.8 billion due to animal mortality, intense labor demands, and strict export bans.

What is the Screwworm?

Despite the name, the culprit is not actually a worm. It is the larval stage of the parasitic fly Cochliomyia hominivorax. 

Unlike common blowfly maggots, which only consume dead, decaying tissue, screwworm maggots feed exclusively on the living flesh of warm-blooded hosts.

An adult female fly locates a host and lays up to 400 eggs in any break in the skin. The eggs hatch within 12 to 24 hours, and the larvae immediately begin burrowing deep into the animal's muscle tissue, quite literally eating the host alive. If left untreated, an infested animal can die in less than a week.

Why Milam County is Vulnerable

Because the fly has been eradicated from North America for decades, today's herds have zero natural immunity, and younger generations of stockmen have never had to manage it. Daily ranch operations that break the skin—such as tagging, dehorning, branding, or scraping against a barbed-wire fence—create an immediate entryway for the parasite.

State animal health experts emphasize that preparation is key to stopping a widespread outbreak before it can devastate local economies.

“TAHC has been actively preparing for a resurgence of NWS for over two years,” said Dr. Bud Dinges, TAHC State Veterinarian and Executive Director. “We are putting these preparations into action, and we encourage all animal owners and caretakers to continue to remain vigilant for the presence of larvae in animal wounds and immediately report any suspicions.”

Local officials stress that the U.S. food supply remains 100% safe. Federal agencies have noted that screwworms do not infect processed meat, fruits, or vegetables, and strict commercial inspections prevent any infected animal from ever entering the supply chain. The danger is entirely one of animal welfare and ranch biosecurity.

The State’s Strategic Defense

The government is responding using the same biological weapon that eradicated the pest in the 1960s: the Sterile Insect Technique (SIT). 

Because female screwworm flies only mate once in their lifetimes, state and federal agencies are releasing millions of laboratory-raised, sterilized male flies via aircraft and ground chambers in affected zones. When wild females mate with these sterile males, they produce no offspring, collapsing the local population cycle.

However, with a massive new $750 million domestic sterile fly production facility under construction in Edinburg, Texas, state officials are racing against the clock. Governor Abbott noted that the timeline must be moved up to ensure long-term eradication.

“This is likely to spread over the course of the summer. During winter months, it may kill off the flies or reduce their number, but we can't make it through a second summer,” the governor warned, adding that he is pushing federal regulators to finish the Texas facility ahead of schedule. "The United States has defeated this pest before, and we will do it again."

Rancher Checklist: Inspect, Report, Protect

Local producers should immediately implement the TAHC’s three-pronged protocol to shield their livestock:

• 1. Inspect Daily: Closely examine all livestock, especially newborn calves (checking the umbilical area), recently castrated or branded animals, and any stock showing signs of lethargy or scratching. Wounds may look unusually enlarged, produce a foul odor, or seep dark fluid.
• 2. Delay Elective Procedures: If possible, postpone non-essential surgical procedures (such as dehorning or cosmetic tagging) until cooler months, or ensure animals are heavily protected with topical repellents.
• 3. Treat and Protect Wounds: Clean and treat even the smallest abrasions—including fly or tick bites—with government-approved larvicides or wound dressings to prevent adult flies from landing.

How to Report Suspected Cases:

If you find unusual maggot activity or a wound that is deep, foul-smelling, and refusing to heal, do not attempt to move the animals or remove the larvae yourself. Contact your local veterinarian immediately, or report it directly to the Texas Animal Health Commission at 1-800-550-8242.